understanding stealth and aircraft survivability - amazon web

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A MITCHELL INSTITUTE STUDY

The Radar GameUnderstanding Stealth and Aircraft Survivability

By Rebecca Grant September 2010

A mitchell inStitute Study

On September 12, 1918 at St. Mihiel in France, Col. Wil-liam Mitchell became the first person ever to command a major force of allied aircraft in a combined-arms opera-tion. This battle was the debut of the US Army fighting under a single American commander on European soil. Under Mitchell’s control, more than 1,100 allied aircraft worked in unison with ground forces in a broad offen-sive—one encompassing not only the advance of ground troops but also direct air attacks on enemy strategic tar-gets, aircraft, communications, logistics, and forces beyond the front lines.

Mitchell was promoted to Brigadier General by order of Gen. John J. Pershing, commander of the American Expeditionary Force, in recognition of his com-mand accomplishments during the St. Mihiel offensive and the subsequent Meuse-Argonne offensive.

After World War I, General Mitchell served in Washington and then became Commander, First Provisional Air Brigade, in 1921. That summer, he led joint Army and Navy demonstration attacks as bombs delivered from aircraft sank several captured German vessels, including the SS Ostfriesland.

His determination to speak the truth about airpower and its importance to America led to a court-martial trial in 1925. Mitchell was convicted, and re-signed from the service in February 1926.

Mitchell, through personal example and through his writing, inspired and en-couraged a cadre of younger airmen. These included future General of the Air Force Henry H. Arnold, who led the two million-man Army Air Forces in World War II; Gen. Ira Eaker, who commanded the first bomber forces in Europe in 1942; and Gen. Carl Spaatz, who became the first Chief of Staff of the United States Air Force upon its charter of independence in 1947.

Mitchell died in 1936. One of the pallbearers at his funeral in Wisconsin was George Catlett Marshall, who was the chief ground-force planner for the St. Mihiel offensive.

ABOUT THE MITCHELL INSTITUTE FOR AIRPOWER STUDIES: The Mitchell Institute for Airpower Studies, founded by the Air Force Association, seeks to honor the leadership of Brig. Gen. William Mitchell through timely and high-quality re-search and writing on airpower and its role in the security of this nation.

Brig. Gen. Billy Mitchell

Published by Mitchell Institute Press© 2010 Air Force AssociationDesign by Darcy Harris

ABOUT THE AUTHOR: Dr. Rebecca Grant is an airpower analyst with 20 years of experience in Washington, D.C. She is President of IRIS Independent Research and serves as director, Mitchell Institute, for the Air Force Association. She has written extensively on airpower and among her most recent publications are several Mitchell reports, including The Vanishing Arsenal of Airpower (2009), The Tanker Imperative (2009), and Airpower in Afghanistan (2009).


By Rebecca Grant

September 2010A mitchell inStitute Study


FOREWORD 6

INTRODUCTION 8

SURVIVABILITYBEFORERADAR 10

THERADARGAMEBEGINS 15

THEPOSTWARRADARGAME 23

WINNINGTHERADARGAME 29

SIGNATUREREDUCTIONANDMISSIONPLANNING 36

LOWOBSERVABLESINTHEOPERATIONALENVIRONMENT 44

CONCLUSION:THEFUTUREOFSTEALTH 53

ENDNOTES 56

THE RADAR GAME: Understanding Stealth and Aircraft Survivability

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Radio aids to detection and ranging ... radar—as it’scommonly called—transformed air warfare in 1940. It

hasheldagriponwould-beattackersanddefenderseversince.

ThisspecialreportfromtheMitchellInstituteforAirpowerStudies isarepublicationofa longessay Iwrote in1998togetatwhystealthwassuchanimportantbreakthroughforairpower.Then,asnow,therewerequestionsaboutthefutureofstealth.

Consider the times. The dazzling combat success of theF-117intheGulfWarof1991hadbeenfollowedbythecan-cellationof theB-2 stealthbomberprogram in1992.Cuts totheF-22stealthfighterprogramhadalreadybeenmade.Ex-periencedairmenwere strongly in favorof stealth. Someof-ficials,likeformerSecretaryofDefenseWilliamPerryandthen-UndersecretaryofDefenseforAcquisitionPaulKaminski,werethoroughlysteepedintheworkingsofstealthanditsbenefits.But for many, intricate stealth programs seemed a question-able investmentgiven thedecliningdefensebudgetsof thelate1990s.Stealthwaswrappedupinthevalueofairpowerasawholeandinthere-evaluationofAmericansecuritypolicies.

Still,adozenyearsagotherewasastrongcommitmenttostealth.TheAirForce,Navy,andMarineCorpsalongwithBritainhadcommittedtotheJointStrikeFighter.TeamsledbyLockheedMartinandBoeingwereworkingondesigns.Per-hapsmostimportant,thelong-rangeAirForcebudgethadaplantofieldanall-stealthfighterforceofmorethan2,200fighters.Thefutureofstealthseemedassured.

Combat experience quickly revalidated its importanceduringthe1999NATOairwarwithSerbia.B-2sflewmissionsintoheavilydefendedairspaceanddideverythingfromtak-ingouttheNoviSadbridgetoattackinganddestroyinganSA-3surface-to-airmissilebattery.F-117sflewcrucialmissions.(OneF-117wasshotdown.)TheintensiveairwarwithIraqinearly2003againsawtheuseofbothF-117sandB-2sagainstavarietyoftargetsinandaroundBaghdad.

Sincethen,stealthhascomeunderassault.The reasonshave much to do with strategy, politics, and budgets, andlittletodowiththecapabilityassessmentsthatdrovethede-cisionstodevelopandbuystealthaircraftinthefirstplace.

Theradargameitself is justascriticalas itwasadozenyearsago.Radarremainstheleaderintechnologiesforde-tectingaircraftandmissileattack.Asthestudynotes:“Whywereaircraftsovulnerabletoradardetection?Inshort,forallthereasonsthatincreasedtheiraerodynamicqualitiesandperformance.Metalskins,largeverticalcontrolsurfaces,bigpowerfulengines”andsoon.

Thestudydetailshowthefirstroundsoftheradargamewere all about electronic countermeasures. RAF BomberCommandfamouslyheldbackthefirstuseofchaffforoverayear,fearingthattheGermanswouldimplementcounter-measures,too.DuringtheColdWar,electroniccountermea-suresandelectroniccounter-countermeasuresbecameoneof theblackestartsofairpowerandoneof itsmost impor-tant.Stealthwasinpartawaytobreakthetug-of-war.

That was why stealth was so attractive. Attackers mustundotheadversary’sadvantageeitherbylow-levelingress,high-altitude operations, speed, electronic countermea-sures,orstealth.Ofthese,theabilitytodiminishtheeffectsofradarreturnisoneofthemostchallengingandoneofthemostrewarding.Alowobservableaircraftgainsadvantagesin how close it can come to air defense systems. Low ob-servableaircraftdonotgetafreepassinthebattlespace.Lowobservabilityhastobefine-tunedtodefeatadversarysystemsastheyestablishandhand-offtracksandzeroinonfirecontrolsolutions.Notmuchwillpreventthebigbumpoflong-range, low frequency radarsused for initialdetection.But,ittakesmuchmorethanablipona“TallKing”radartounravelawell-plannedmission.

Over thepastdecades, it’sneverbeeneasytoconveywhatlowobservabletechnologiesactuallydo.Understand-ingthemrequiressomegraspofphysics,ofradarphenom-

Foreword

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enology,ofaircraftdesign,ofhowmissionsareplannedandexecuted. One hears so often that stealth is not invisibility.The inversecorollary is thata single radardetectionofanaircraftatapointintimeandspacedoesnotequalanim-penetrablebattlespace.TheBritishnickname“ChainHome”fortheircross-Channelradarsuitehaditaboutright.Ittakesa chain of detections, interpretations, and correct actionsbydefenderstointerceptanaircraft.Stealthbreaksupthechain by removing, reducing, or obfuscating a significantpercentageofthosedetectionopportunities.

MuchofThe Radar Game isdevotedtoabasicdiscus-sionofhowstealthworksandwhyitiseffectiveinreducingthe number of shots taken by defensive systems. Treat thislittleprimerasa steppingoffpoint fordiscoveringmoreofthecomplexitiesoflowobservability.

Ofcourse,thereisawiderelectromagneticspectrumtoconsider.Whileradar isthefocushere,truesurvivabilityde-pends on taking measures to reduce visual, acoustic, andinfraredsignaturesaswellasminimizingtelltalecommunica-tionsandtargetingemissions.

Thedarlingofpassivetechnologiesisinfraredsearchandtrack.Thoseincombatignoretheinfraredspectrumattheirperil.Although it is not as often in the headlines, designersofall-aspectstealthaircrafthaveworkedsincethe1970stominimizeinfraredhotspotsonaircraft.

Finally,electroniccountermeasuresstillhavetheirroletoplay.Asbefore,itwilltakeacombinationofsurvivabilitymea-surestoassuremissionaccomplishment.

The Radar Gameshouldalsoshedlightonwhycomplextechnologies like stealth cost money to field. The quest forstealth is ongoing and the price of excellence is nothingnew.Take,forexample,theP-61BlackWidow,whichwasthepremier US night fighter of lateWorldWar II. This all-black,two-engine fighter was crewed by a pilot in front and adedicated radar operator in the back seat. Its power andperformance were terrific advances.“All this performance

OriginalCopyright1998RebeccaGrant

Acknowledgements from 1998 version: The author would liketo thankDr. ScottBowden forhisassistancewithhistorical re-search.Also,theauthorwouldliketoextendspecialthankstoTomMcMahon,PhilSoucy,KenMcKenzie,andCharlesMasseyofModernTechnologySolutionsInternational,ofAlexandria,VA,forconductingthesimulationsofsignatureshapesinanairde-fenseenvironmenttoillustratethetacticalbenefitsofstealth.

camewithahighpricetag,”notedStevenL.McFarlandinhis1997AirForcehistoryConquering the Night.“WithNorthrop’sassemblylineinfullgear,acompletelyequippedP-61cost$180,000in1943dollars,threetimesthecostofaP-38fighterandtwicethepriceofaC-47transport.”

Winning the radar game still carries a substantial pricetag—but stealth aircraft pay back the investment in theircombatvalue.

Stealthremainsattheforefrontofdesign.Oneofthebestsignals about the ongoing value of stealth lies in new ap-plications.Leadingunmannedaerialvehiclesforhigh-threatoperations incorporate stealth. Navy ships have adoptedsome of its shaping techniques. Of course, the F-35 JointStrikeFighter remains thenation’s singlebiggestbeton fu-tureairpower.

Success in the radar game will continue to govern thevalue of airpower as a tool of national security. Many ofAmerica’suniquepolicyoptionsdependuponit.WhenandiftheSA-20joinsIran’sairdefensenetwork,itwillmakethatnationaconsiderablytougherenvironmentforairattack,forexample.Alreadythereareregionsoftheworldwhereonlystealth aircraft can operate with a good chance of com-pletingthemission.

Infact,stealthaircraftwillhavetoworkharderthanever.Themajordifferencefrom1998to2010isthatdefenseplansnolongerenvisionanall-stealthfleet.TheAirForceandjointpartnerswilloperateamixtureoflegacy,conventionalfight-ersandbombersalongsidestealthaircraftevenastheF-35sarriveingreaternumbers.Theradargameof2020and2030willfeaturealotofassistsandthetacticsthatgoalongwiththat.

Rebecca Grant, DirectorMitchell Institute for Airpower Studies

September 2010


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Precision weapons and rapid targeting informationmean little if aircraft are unable to survive engagementswithenemyairdefenses.Inadditiontocostingthelivesofpi-lots,highlevelsofattritioncanultimatelyaffecttheoutcomeofthetheatercampaign.Oneofthemostcriticalfactorsindeterminingthesuccessofanairoperationissurvivability.Inthelastseveraldecades,thetermsurvivabilityhasbeenas-sociatedwithanalysisofhowlowobservablesandelectron-iccountermeasurescanhelpaircraftcarryouttheirmissionsin hostile airspace. Discussions of survivability immediatelybringtomindstealthaircraft, radar jamminganddebatesaboutthelatestSA-10threats.YetthequestforsurvivabilityisnotafadoftheColdWarorthehigh-technology1990s.Itsroots,anditsimportancetocombinedarmsoperations,gobacktothefirstuseofmilitaryaircraftinWorldWarI. Since the earliest days of military aviation, pilots andplannershavetakenadvantageofwhatever theiraircraftcanoffertoincreasetheoddsofsurvivability.Aircraftsurviv-abilitydependsonacomplexmixofdesign features,per-formance,missionplanning,andtactics.Theefforttomakeaircrafthardertoshootdownhasconsumedalargeshareofthebrainsandresourcesdedicatedtomilitaryaircraftde-signinthe20thcentury. Since the 1970s, the Department of Defense has fo-cusedspecialeffortonresearch,development,testing,andproductionofstealthaircraftthataredesignedtomake itharderforairdefensestoshootthemdown.Lowobservable(LO) technologyminimizesaircraft signature in radar, infra-red, visual, and acoustic portions of the electromagneticspectrum,creatingstealth.FutureplansfortheAirForceF-22andthetri-serviceJointStrikeFightercall for thenationtocontinuetoprocureadvanced,LOaircraftforthemilitaryofthe21stcentury. Thisessaytellsthestoryofhowthebalancebetweentheairattackerandairdefenderhasshiftedovertime,andhowtheradargamechangedthenatureofaircraftsurvivability.

Examining the evolution of this balance provides a betterunderstandingof thechoices facingmilitarycommandersanddefenseplannersastheyconsiderwhatformsofsurviv-abilitytechnologyareneededtopreservethedominanceofAmericanairpower. To begin with, the financial and strategic investmentin stealth aircraft is one that not everyone understands.Stealth technology was developed and tested in secret.F-117 stealth fighter squadrons were practicing night mis-sionsintheNevadadesertseveralyearsbeforetheAirForcepubliclyacknowledged theaircraft’sexistence.Evenafterthe F-117’s impressive performance in the 1991 Gulf War,an element of mystery and misunderstanding sometimessurrounds the operations of stealth aircraft. The F-117 andthe B-2 stealth bomber have the ability to complete andsurvivemissionsthatotheraircraftcannot.Still,forthemostpart, thegovernmenthasgivenonly themostcondensedandsuperficialexplanationsofwhattheselowobservableaircraftcandoandwhytheirmissionissoimportanttojointoperations.Inaddition,themechanicsofradarcrosssection(RCS)reductionandtheeffectoflowersignaturesintacticalscenariosareseldomdiscussed. This essay will reveal no technical secrets or surprises.Whatitwilldo,however,isexplainhowtheradargamebe-came a major factor in air combat; how LO technologygained the upper hand in the radar game; and how theoperational flexibility provided by low observable aircrafthasbecomepivotaltoeffectivejointairoperations.

The Origins of Aircraft Survivability Survivability—defined as the ability of the aircraft andaircrewtoaccomplishthemissionandreturnhome—hasal-waysbeenanimportantfactorindeterminingtheeffective-nessofairoperations.EarlyinWorldWarI,theuseofaviationforces incombat revealedthatsurvivabilityconsiderationswould influence mission effectiveness. Efforts to improve

INTRODUCTION

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survivability quickly began to influence aircraft design asspecializedaircrafttypesemergedby1915.ThewholeideaoftheSpadXIIIfighterplane,forexample,wastocombinemaximum speed and maneuverability to dominate aerialengagements.BomberssuchastheGermanGothaortheBritish Handley Page had a different mission and accord-inglydrewondifferentsurvivabilitymeasures.Theyreliedonself-defense guns and armor plating for survivability sincetheirextrarangeandpayloadprecludedmakingthemostofspeedandmaneuver. As aircraft survivability started to contribute to aircraftdesign,aircraftwerebecomingmoreimportantcontributorstocombinedoperationswithgroundforces.Aircrafthadtobeabletooperateoverenemylinestoreconnoiter,correctartilleryfire,andwardoffenemyairplanestryingtodothesame.By1918,aircraftwereanimportantelementofcom-bined arms operations because of their ability to extendthebattledeepbehindenemylines.“Theattackofgroundobjectivesinthezoneasfarbackoftheenemy’sfrontlinesas his divisional posts of command often yields importantresults,”notedaGeneralStaffreportin1919.“Thegreatmo-bilityandspeedofairplanesmakeitpossibletoutilizedaybombardmenttacticallytoinfluenceanactioninprogress,”continuedthereport.1

ThelastcampaignsofWorldWarIhintedthatairsuperi-oritywouldbenecessaryforthemosteffectivegroundop-erations,butWorldWarIImadeitanironlaw.However,theinventionofradarontheeveofWorldWarIIchangedtheaircraft survivabilityproblemcompletely. InWorldWar I, vi-sualdetection incleardaylightdidnotexceed rangesof10-15milesatbest.Eveninthelate1930s,defendersexpect-edtolistenandwatchforattackingaircraft. By 1940, radar could spot incoming aircraft 100 milesaway. Early detection gave defenders much more timeto organize their air defenses and to intercept attackingplanes. Radar height-finding assisted antiaircraft gunnersontheground.Primitiveairborneradarsetswereinstalledinnightfighters inthelateryearsofthewar.Theradargamehadbegun.Gainingairsuperiorityandthefreedomtoat-tacksurfacetargetswhileprotectingfriendlyarmiesrestedonsurmountingtheadvantagesthatradargavetoairde-fenses. The stakes of the radar game also affected com-binedarmsoperationsinalltheatersofthewar.Hitlercan-celedtheinvasionofBritainwhentheLuftwaffefailedtowinlocalair superiorityover theEnglishChannelcoast inSep-tember1940.TheAllieshingedtheirplansfortheNormandylandingsongainingcontroloftheairoverEuropeandex-ploitingitwitheffectiveairinterdiction.Therateatwhichair-powercouldaccomplishitsobjectivesthereforedependeddirectlyonsurvival ratesof thebombersattackingaircraftfactoriesandindustrialtargetsinFortressEurope.OncetheAllieswereashore,theyplannedforairpowertohelpoffsetthenumericalsuperiorityofGermangroundforces.

TheColdWarmadeaircraftsurvivabilityevenmorecom-plicated.AfterWWII,radartechnologyleaptaheadandair-craftdesignsstruggledtomaintainasurvivabilityedge.Bythe 1960s, radar dominated the air defense engagement.Longerrangedetectionradarsprovidedampleearlywarn-ing.Radar-controlledsurface-to-airmissiles(SAMs)improvedthespeedandaccuracyofattacksagainstaircraft. Intheair, more advanced radars and guided air-to-air missileschangedthenatureofaerialcombat.Conventionalperfor-manceimprovementsinspeed,altitudeceiling,maneuver-ability,andotherparameterspushedaheadbutcouldnotkeeppacewiththemostsophisticatedairdefenses.Ifradarmadeaircrafteasy to shootdown, theeffectivenessofairoperationswouldplummet. Asaresult,combataircrafthadtoincorporateaddition-alsurvivabilitymeasurestostayahead intheradargame.Electronic countermeasures (ECM) to radar were first em-ployedinWorldWarII.Researchinthe1950sand1960sledtomuchmoreadvancedcountermeasures thatdisruptedradar tracking by masking or distorting the radar return.Whenaircraftgotclosertotheairdefenses,however,theirradar reflections grew large enough to burn through theelectronicsmokescreenputinplacebyECM.

Winning the Modern Radar Game In this context, the prospect of designing combat air-craftthatdidnotreflectasmuchradarreturnwasanentic-ing possibility. British researchers in the 1940s hypothesizedabout foiling radardetection. Lowobservable technologythatreducedradarreturnwouldmakeitharderfordefend-ers to track and engage attacking aircraft because theywould not have as big an aircraft signature to follow. Lessradar return meant less time in jeopardy, or time in whichaircraftcouldbetrackedandfireduponbyotheraircraftorbyground-baseddefenses. However, coming up with an aircraft design that mini-mized radar returndependedonmany factors. Itwasnotuntiltheearly1970sthatthephysicalprinciplesofcontrollingradar returnwereunderstoodwellenough toapply themto aircraft design. Low observable technology was basedfirstonasophisticatedabilitytounderstandandpredictthebehaviorofradarwavesincontactwithanaircraft. Researchintospecialshapesandmaterialsmadebuild-inga lowobservableaircrafta reality.Theaimwasnot tomakeaircraftinvisible,buttoquantifyandminimizekeyar-easoftheaircraft’sradarreturn.Incorporatinglowobserv-ablesrequiredtrade-offsthatoftenappearedtogoagainstestablishedprinciplesofaerodynamicdesign.Theprimarymethodforreducingradarcrosssectionwastoshapetheaircraft’ssurfacesothatitdeflectedradarreturninpredict-ableways. Variationsintheanglefromwhichaircraftapproachedtheradar,andthefrequencyoftheradarsusedbythede-


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fenders,alsoaffectedtheradarreturnandrequiredchoicesabouthowtooptimizedesignsforthemostdangerouspartsof the cycle of detection, tracking, and engagement. AsRCS diminished, other factors became important corollar-ies,suchasreducingtheinfraredsignatureaswellasvisual,acoustic,andotherelectronicevidenceoftheaircraft’sap-proach. LO design offered immediate tactical benefits by cut-ting radardetection rangesanddegrading theefficiencyofsearchradars.Signaturereductionnowposedsubstantialproblemsforintegratedairdefenses(IADS)becauseitcoulddelayearlywarningdetectionanddiminishtheabilityoffirecontrolradarstoacquireandfireSAMsagainsttheattack-ingaircraft.

Aircraft Survivability and its Operational Impact Thepayoff for lowobservablescame fromdevelopinganaircraftthatcouldtackleeachstageoftheradargame.Lowobservablesofferedaway to regainsomeof thesur-priseelementofairattackandimprovetheoddsineachin-dividualengagement.Overall,LOaircraftwouldspendlesstimeinjeopardyfromairdefensesandstandamuchbetterchanceofcompletingthemissionandreturninghome. The tactical benefits of increased aircraft survivabilityopened up a wide range of options for air commanders.Most important, spending less time in jeopardy could re-duceattritionratesbyloweringtheprobabilityofaircraftbe-ingdetected, tracked,andengagedduring theirmissions.

Highly survivableaircraftcouldbe tasked toattackheav-ilydefendedtargetswithmuchlessrisk.Asaresult,desiredeffects—suchasdegradingenemyairdefenses—couldbeachieved in a shorter period of time. Critical targets thatmight have taken repeated raids from large packages ofconventionalaircraftcouldbedestroyedinasinglestrikebyamuchsmallernumberofF-117sabletopenetratecloseenoughtouselaser-guidedbombs(LGBs). The final section of this essay quantifies the effects ofsignature reduction in the tactical environment. Graphsshow how reduced signatures lower the time in jeopardy,andhowstealthdegradesdetectionbyearlywarningradarandsubsequent trackingandengagementbyfirecontrolradars.Threehypotheticalscenariosdisplaytheresultsoftheanalysis inhighand lowthreatenvironments.Variations foraltitudeandattackprofileareincluded.Ashortsectionalsodiscusses in general terms the potential synergy betweenlowobservablesandelectroniccountermeasures. SinceWorldWar II, the radargamebetweenattackersanddefendershasdeterminedwhowillcontroltheskies.Thewinneroftheradargamewillbeabletobringthemaneu-verandfirepowerofair forces tobearagainst theenemy.Forthe21stcentury,highlysurvivableaircraftwillcontributedirectlytoachievingjointforceobjectives.Theywilldothisbyshapingandcontrollingthebattlespacewherejointairandsurfaceforcesoperate.Theabilitytoprojectpowerwithefficientandeffectiveairoperationswilldependonwinningtheradargame.

The best way to understand the impact of radar isto lookbackat thefirstairwar.WorldWar Iduels in theairdefinedwhatittooktoprevailinaircombatandwhysurvivabilityratesintheaircomponentwereimportanttocombinedarmsoperations. Survivabilityinthemostbasicsensereferstotheabil-ityofanaircraftand itscrewtocarryout itsmissionandavoidbeingshotdown.Beforethedevelopmentofradar,controloftheaircenteredonaduellimitedtothefieldofviewofthehumaneye.AircombatinWorldWarIbeganwhenenemypilotsorgunnersonthegroundspottedat-tacking aircraft. To control the skies, the biplanes had tosurvivetheduel.Carryingoutmissionsandassistingforcesonthegrounddependedonensuringthatenoughaircraftandcrewswouldsurvivetofightinstrength,dayafterday. SurvivabilitywasasimportanttoairoperationsinWorldWarIas it istoday.Thetechnologyandtacticsweredif-ferent,butthebasicfeaturesoftheduelforcontroloftheskiesweremuchthesame.Theessentialelementsofthe

air-to-airengagementandtheproblemofground-basedairdefensetookclearshapebetween1914and1918.

Elements of the Duel AircombatinWorldWarIwasaduelbetweenattackersanddefendersforcontroloftheair.Toperformtheirmissions,aircraft had to survive encounters with hostile aircraft andwithenemygroundfire.Theirchanceofsurvivaldependedonthetechnicalabilitiesoftheaircraftandonthetacticalskillwithwhichtheywereemployed. Itmayseemstrangetospeakofthe“survivability”ofbi-planes with fabric wings and wooden two-bladed propel-lers.WorldWarIaircraftwereextremelyvulnerabletoclose-inattack.France,Germany,Britain,andotherwarringnationsconsumedaircraftatstaggeringrates,runningthroughsup-pliesoftensofthousandsofmachines inthecourseofthewar.Accidents,poormaintenance,dirt runways,andevenexposuretotherainandwindclaimedaheavytoll.Pilotin-experiencealsocontributedtolossrates.

SURVIVABILITY BEFORE RADAR

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However,WorldWarI’sairwarsketchedoutelementsoftheduelforsurvivabilitythatwouldreappearinaircombatinWorldWarII,Korea,Vietnam,andDesertStorm.Byfocus-ingonhowthesurvivabilityduelemergedinWorldWarI,itispossibletosetabaselineforunderstandinghowevolutionintechnologyhaschangedthesurvivabilitydueltoday. EncountersbetweenattackersanddefendersinWorldWarIoutlinedthreepartstotheirduel:detection,engage-ment,andprobabilityofkill.Detection refers to the taskofspotting and tracking enemy aircraft. Engagement repre-sents a defending fighter attempting to close in during adogfight,orground-basedairdefensestrackingandaimingat incomingaircraft.Probabilityofkill involvesanumberoffactors. In its simplest form, itassumes theaircraft ishit,butthechanceofdestroyingtheaircraftdependsonthenatureandextentofthedamagesustained. Thedefenderattemptstocompleteeachstage.With-outdetection,noengagementispossible.Withoutengage-ment, there isnoprobabilityof kill.On theotherhand, theattacker’staskistothwartthedefenderateachstage.Ide-ally, theattackerwouldenjoycompletesurpriseandarriveoverthetargetareaundetected.Ifdetected,pilotsevadeorprepareforengagement.Ifengaged,theyseektodestroyoravoidenemyaircraftandtododgeenemysurfacefire.Iftheaircraftishit,probabilityofkillwoulddependonthenatureandextentofthedamage. Thedistinctionsbetweenthethreephasesareartificialfromtheaircrew’sperspectivebecauseeachstageblends

into the next. However, analyzingeachstagehelpstoillustratethepro-cessofachievingsurvivability.

Detection Thefirst task in theduelwas tofindthe enemy, and inWorldWar I, therewas little that technology could dotoassist in theprocess.Detectionde-pendedalmostexclusivelyonthehu-maneye.Defendersintheairoronthegroundhadtoseetheairplane,hearit,orperhapsbeshotatbyit,inorderto know itwas there. In thedaysbe-fore radar,noothermeansexisted todetect and track enemy aircraft. TheWorldWarIaviatordidnotevenhaveacockpit radio to report locationsofenemyaircraft. Defenders constantly struggled togain early warning of air attack. Air-planes could often be heard beforetheywereseen.Pheasants,thoughttohave acute hearing, were placed atFrench listening posts to warn of ap-proaching aircraft. In England, audio

detectionformedpartoftheairdefensescreenaroundLon-don. Bothsidesmountedfrequentpatrolstoseekoutandde-stroyenemyaircraft.Whentroopsonthelinespottedaircraft,reports were relayed by telephone to the airfields. Airfieldcommandersmightlaunchplanesintimetointercepttheat-tackers.ThefirsttwoAmericankillsofthewarcamefrompilotsscrambledtointerceptGermanaircraftpatrollingoverfriendlylines. Oncetheaviatorcouldseehisopponent,bothwerevul-nerabletotheformidableshort-rangetrackingcapabilitiesofthehumaneye.Theshortrangeofvisualdetectionplacedapremiumontheelementofsurprise.“Thedecidingelementinaerialcombatisusuallysurprise,”explainedanairserviceman-ualin1919,sothe“enemywillemployallmeansathisdisposaltoconcealhisapproach.”2Inaircombat,aircraftmighthavetoclosetowithin50yardsforagoodshotattheopponent.

Deceiving the Eye A fewmeansexisted to thwartopticaldetection.Hid-inginclouds,attackingoutofthesun,and,mostofall,ap-proachingfromaboveandbehindtheaircraftdelayedop-tical detection. Camouflage paint schemes blended wingsurfacesintothecolorsoftheterrainbelow. However,thesinglemosteffectivemeasureagainsttheenemy’sability todetectand interceptwastoflyatnight.WorldWarIaircraftcouldoperatealmostatwillundercover


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ofdarkness.Onabrightmoonlitnightenemyaircraftcouldbeseenatjust500-600yards;instarlight,theirdarkshadowsmaterializedat200yardsorless.Asonescholarsummarized:

“There were several ways to meet the threat posed by the fighter: One was to increase the bomber’s capability to defend itself; another was formation flying, which allowed planes to put up a collective defense; and a third was to have the bombers escorted by fighting craft of one’s own. But the most effective response for planes with long‑distance missions was simply to carry out those missions at night. The enemy fighter, so formidable by day, did not even attempt night interceptions until the end of the war.”3

Bothsidestookadvantageofthecloakofdarknesstoreach deeper into enemy territory in search of iron works,concentrationpoints,supplydepots, railroadsandother lu-crativetargets.Basesandtownsalongthefrontblackedouttheirlights.Onnightswithbrightmoonlight,Germanbombersroutinely attacked French border towns such as Nancy. Bylate1917,mostofthecitywasevacuatedand“caveshadbeenbuiltalongthestreetsinwhichpassers-bycouldtakerefuge in case the airplanes came,” Billy Mitchell noted.4

Searchlights and anti-aircraft guns did little to stop the at-tacks.Ononemoonlitnight,GermanGothabombersscoredtwodirecthitsonanammunitionfactoryinNancy,knockingit out of production for the remainder of the war. Describ-inganothernightraidnearhishotel,Mitchellwrotethat“theanti-aircraftgunswerefiringatthesoundoftheairplanesasmuchasanythingelse.”5

Thelackoflongrangedetectionlinkedtoanintegratedcommandandcontrolsystemmeantthatforthemostpart,airoperationsinWorldWarIdidnotencounterwell-or-ganized antiaircraft gun defenses.Enemyantiaircraftdefensescouldhesevere at times and non-existent atother times. For the attacker, the sur-vivability duel with ground defenseswas one over which pilots felt theywerethemasters. “No,wehadlittlerespectfortheantiaircraftgun—unlessitwasprotect-ing a balloon,” wrote Eddie Ricken-backer.Pointdefensesaroundknowntargets like balloon emplacementscould be lethal because they ben-efited from many of the advantagesthatwouldbe featured in integratedair defenses decades later. Balloondefense crews knew their“sausages”were high value targets that wouldattract air attacks. Because balloons

operated at fixed altitudes as well as fixed locations, gun-nersprotectingthemcouldaimatexpectedattackroutes.Theycouldalsopredictthealtitudeoftheattackandsetthefusesoftheantiaircraftartilleryaccordingly.AsRickenbackerdescribedit:

“If the balloon was two thousand feet up, then any aircraft attacking it must also be at or near the same altitude. When we came in to attack a balloon, therefore, we flew through a curtain of shells exploding at our precise altitude. We had to fly at that altitude for several seconds, for it took a long burst to ignite the gas. ... After the attack it was necessary to fly out through the wall of Archie on the other side.”

Finally,Rickenbackeradded,“Balloonswereofsuchmili-taryimportancethat,frequently,flightsofFokkerswouldbehoveringabovethem,hidingupthereinthesun.”6

Pilotreportsfromairoperationsin1918documentedev-erything from heavy but inaccurate antiaircraft fire all thewaytothetarget,toverylightornon-existentfire.Still,Rick-enbacker’sdescriptionforeshadowedthelethalairdefenseenvironmentofWorldWarIIandbeyond,whenthelimitsofoptical detection would be overcome and aircraft wouldlosemuchoftheiredgeinsurpriseattack.

The Engagement: Designing Aircraft to Survive With advance warning and detection limited to therangeofthehumaneye,thekeytosurvivabilityinWorldWarIwastoprevailintheengagementphase.Structuraldesignfeatureswereparamount. The warring nations entered the conflict with general

13


purposeaircraftintendedmainlyforreconnaissance.Buttheairwarquicklyplacedapremiumonaircraftdesigned forspecializedmissions.Inadogfight,speed,rateofclimb,andmaneuverability could significantly influence the outcome.Asoneaviatorlaterwrote:

“The war has shown that there is no universal or multiple pur‑pose plane, which can be used for pursuit, reconnaissance and bombing work. Each particular work calls for a different type of plane, specializing either in speed, maneuverability, climbing ability, carrying capacity, or long distance range. In order to embody one of these characteristics in a plane, others must be sacrificed.”7

By1915,thenewaircraftdesignsreflecteddistinctmis-sion requirements. Survivability features were tailored toeachtype. Forexample,thewholeideaofapursuitaircraft—afight-er,intoday’sterms—wastoseekoutandengageenemyair-craft,andshootthemdown.Speedandperformancegaveaskilledpilotanadvantageoverhisopponents.TheBritishcheeredthearrivaloftheirfastandagileSopwithCamelsin1917.TheGermanFokkerDVIIwasoneofthebestmachinesofthewarbecauseofitsincreasedspeed,maneuverability,andperformance.In1918,aFrenchpilotwrote:“Daysofhighspirits!WehavereceivedSpads!Nowwe’refinallygoingtoshowtheFritzesaboutspeedandmaneuverability.”8Ameri-canace-to-beEddieRickenbackermadeaspecial trip toParisthatsummertopickuphisnewFrench-builtSpadXIII. Where mission requirements diversified, so did surviv-ability features. Some pursuit aircraft, such as Britain’s Sop-withSalamander,werebuiltasarmoredtrench-fighters.Ma-chinegunspointedthroughthefloorofthecockpitand640poundsofarmorplatingprotectedthefuselagefromriflefireataltitudesaslowas150feet.9

Inanentirelydifferentclass,observationaircraftcarriedtwo pilots and more guns because they could not rely onrawspeedintheirdangerousmissionsoverthelines.Experi-encedFrenchobservationpilotscounseledAmericantrain-eesaboutthedangersfromthefasterenemyaircraftpursu-ingthem:“Yourplaneswillbeslower,lessmaneuverable.Donothesitatetorun.”10Additionalself-defensefeaturessuitedtheirmissionofcrisscrossingandlingeringoverenemylinesatloweraltitudes.Therearobserverwasarmedwithamachinegun.DedicateddesignssuchastheSalmsonincorporatedamoreruggedairframeandarmorplating. Self-defense firepower was also the prime ingredientin survivability for thebiggerandslowerbombardmentair-craft.Asonepilotputit,“Inasmuchasnobombingplanecanhopetorunawayfrompursuitplanes,itsdefensivepowerliesinthestrengthoftheformation.”11

AHandleyPagebomberclocked95mph.ThiswasnomatchforaSpadXIII,stapleofthelateryearsofthewar,which

couldreach120mph.Pursuittacticsofthedayfrownedonescortingthebombers.Instead,pursuitgroupsmetbombersovertheirtargetstoengageenemyaircraft,andagainwhenthebomberformationcrossedovertofriendlylines.Bombersspentmostoftheirmissionsinjeopardywithonlyamachinegunnerseatedbehindthepilottoputupanarcofdefen-sivefire.“Agoodformationofbi-placemachinescanfightoffdoublethenumberofpursuitplanes,”contendedabomberpilotafterthewar.12

Probability of Kill Thefinalphaseofthesurvivabilityduelconsistedofthelikelihoodorprobabilitythatshotsfiredduringtheengage-mentwoulddisableanddown theaircraft.Analystswouldlatertermthis“probabilityofkill.”Dependingonthesystemsinvolved,theprobabilityofkilldependedonanynumberofcomplexvariables. Aircrews sought to control these variables where pos-siblejustastheydidinallphasesoftheduel.Throughtacticsandpersonalpreferences,WorldWarIpilotsstrovetoprotectthemselveswhileensuringthatshotsfiredwouldbelikelytohittheirmark.Someaviatorshadtheirmechanicshand-loadammunition belts to help prevent the guns from jammingduringadogfight. Once hit, structural factors could determine whetheror not the aircraft survived to return to base. Bullets mighthitoil lines. Steepdivesmight tear fabricoffwings.On theother hand, armor plating could protect the pilot and thestructural integrity of the aircraft. Near-misses became thematerial for legendsof thefirstairwar.At thesametime, iftheaircraftwasdetected,engaged,andfiredupon,designfactorsmightstillsaveit. Eachstageoftheduelforsurvivabilitycontaineditsowncomplexvariables.Solvingthemandmaintainingtheopera-tionalstrengthoftheairarmwasanimportanttaskbecauseofthegrowingroleofairincombinedarmsoperations.

Survivability and the Air Campaign AircraftsurvivabilitybecameimportantinWorldWarInotbecauseofthelegendaryexploitsitproduced,butbecauseeffectiveairattacksbecameavaluableassettocombinedarmsoperations.By1918,controloftheairhadbecomeoneofthedesiredprerequisitesforgroundoffensives.Establishingtemporarycontroloftheairenabledaviationunitstodriveoffenemyaircraftanddenytheminformationabouttheof-fensiveasitdeveloped.Controloftheairalsoallowedpursuitaircraftandbomberstoconductgroundattacksinsupportof army offensives attempting to attack and maneuver tobreakthedeadlystalemateofthewar.TheairwarofWorldWarImarkedthebeginningofatrendinwhichtheaircom-ponentswouldgrowtohaveashapinginfluenceoverthe-aterplansandoperations. The air component’s ability to play an effective role


14

hingedonsurvivability.Lossratesdeterminedhowmanyair-craftandcrewswouldbeavailableforsustainedoperations.Thelossofevenafewaircraftperdaycoulddebilitatetheairarmquickly.Thechartbelowplotsthemathematicalrateofattritionofaforcethatbeginswith1,000aircraft,eachflyingtwosortiesperday. Losing two percent of the force per day would resultin the lossofalmost 70percentof the1,000aircraft in just30days.Withoutreplacements,thenumberofsortiesflownwoulddropbyalmost50percent,greatly reducing theef-fectivenessofairoperations.EvenatWorldWarIproductionrates, no commander could afford sustained attrition andhopetoremainaneffectiveforce. Air tactics and operational employment conceptssoughttomaximizesurvivabilityinordertokeepupeffective-ness.Survivabilityconsiderationsdirectlyinfluencedemploy-mentconceptssuchasflyinginformations.“Theemploymentofa largenumberofpursuitairplanes inattackinggroundobjectivesincreasesthesafetyoftheoperationsbymultiply-ing the targetsatwhich theenemymust shoot,” reasonedMitchell.Asapostwarmanualinstructed,“Bombingandma-chine gunning of ground targets can only be carried outwhenair supremacy isattained.”Air supremacyhadtobe“temporaryat least”ortheloss inmachineswouldexceedthedamagedonetotheenemy.Anexperiencedpilotaloneoverenemylinesmightsurvive.However,thelimitednatureofwhattheloneaircraftcouldaccomplishmeantthatitwasnotworththeriskofthepilot’slife.13

Dailyattritionmatteredespeciallyasseniorcommand-

ersbegantodependonairoperationsasaroutinepartofcombined arms operations. Under the right conditions, airattackscouldbe surprisinglyeffectiveatdisruptingenemyforcesbehindthelines.Idealtargetsforairattackwereforc-es in concentration, either retreating from or marching uptothefrontlines,preferablyintheearlieststagesofamajoroffensive.

“When an offensive is under way large bodies of troops, cav‑alry and transport are being brought up to the line. These targets are large enough to spot from some distance in the air. Fire can be directed on the group and a great amount of material damage as well as moral damage to the enemy can be done.”14

Every major offensive in 1918 used aviation both toharassandstrikeattheenemy’sreservesandsupplies.TheGermans used airpower to sharpen their offensive in thespringof 1918,andby that fall, theAllieswereemployingmass airpower in conjunction with their own efforts to rollbacktheexhaustedGermanlines.Inthefallof1918,atSt.Mihiel,PershinginstructedMitchelltoassembleacoalitionforce to keep German aircraft back from the ground of-fensive and to assist by attacking German forces as theyattemptedtoretreat.Aslongasconditionsforsurvivabilitycouldbemet, theairarmcouldmakevaluablecontribu-tionstocombinedoperations.

The Interwar Years AircraftinWorldWarIusuallycouldnotbedetect-ed in time to organize and integrate air defenses.Thatmeantthatthesurvivabilitydueldependedonspeed, maneuverability, armament, and other ad-vantages in the engagement between aircraft orwithground-baseddefenses. Aviation design in 1920s and 1930s still sought tomaster the duel between attackers and defendersbydevelopingfaster,moreruggedaircraftasbettertechnology emerged. For a long time, defense sys-temsoffered fewadvancesoverWorldWar I in theproblemofdetectingandtrackingaircraft.BoththeGermansandtheBritishdevelopedlisteningdevicestohearincomingbombersatlongrange. Air tactics and doctrine between the wars con-tinued to assume that aircraft would be detectedonlybytheenemy’seyesandears.Surprisecouldstillbe achieved. Cities and armies alike would remainhighlyvulnerabletosurpriseairattack,especiallybylong-rangebombers. In the 1930s, aviation technology started to yieldsignificant advances that appeared to decreasethe vulnerability of aircraft to detection. With theirlong range, speedy mono-wing designs and guns,

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InWorldWar II as never before, the fortunes of airpowerwouldplayanimportantroleinthetheatermilitarystrategyforeachbelligerent.WorldWarIIaviatorsflewinanairdefenseen-vironmentmorelethalandconsistentthananythingthatWorldWarIaviatorshadfoundontheWesternfront.Thebattleforairsuperioritydominatedoperational-levelplansboth forairandforcombinedarmsoperationsacrosstheEuropeantheaterofwar.Controloftheairwasbecomingaprerequisiteforsuccessinmajorgroundoperations. Forthefirsttime,thesurvivabilityandeffectivenessoftheair component was a major weight in the balance of com-bined-armsoperations.Butneithertheaircraftnorthedoctrineoftheinterwaryearswerereadyforthenextphaseofthesurviv-abilityduel. Inthesummerof1938,theGermancorporationTelefunken

wastestingareliableradardevice.Telefunken’sheadofdevel-opment,Prof.Dr.WilhelmRunge,wasreadytodemonstrateitfortheLuftwaffe.Gen.ErnstUdet,aWorldWarIace,wasthenserv-ingasQuartermasterGeneraloftheLuftwaffe,andcameouttoseethetest.Rungerecalled:

“When I explained that it could be used to cover a 50 km area, and that in spite of fog, or at night, it would locate an aircraft easily within that range, his reaction was astonishing. ‘Good God! If you introduce that thing you’ll take all the fun out of flying!’ “16

Udetcorrectlysensedthatradarearlywarningwouldstripattackingaircraftoftheelementofsurpriseandset inmotiona grueling duel between attackers and defenders. The radar

thebomberswereexpectedtobehighlysurvivable.Theycould attack with speed and surprise. Many new pursuitaircraft designs clung to biplane structures for extra ma-neuverability. But the drag from the wing spars of the bi-plane fighters slowed them down. Bombers of the 1920sandearly1930scouldoftenoutrunpursuitaircraft.AsBritishPrimeMinisterStanleyBaldwinsaidin1932:

“I think it is well for the man in the street to realize there is no power on earth that can protect him from bombing. ... The bomber will always get through … .”

Suchthinkingreflectedtherealitythatamassformationcouldneitherbeheardnorseensoonenoughforfightersandantiaircraftgunstodestroymuchofit.Amoreexpertwitness,CarlSpaatz,hadwrittentoacolleaguein1931thatbombersflyingbelow15,000feetwouldneedpursuitaircraftprotection.

However,“ataltitudesabove15,000feetobservationfromthegroundbecomesdifficult,” Spaatznoted,“andabove20,000feet bombardment airplanes can make deep penetrationswithoutpursuitprotection.”15TheanalysisbySpaatzwasbasedonrealisticassumptionsforthetime. Toanobserver in themid- to late-1930s, the survivabilityduelcontainedmuchthesameelementsithadin1918.Detec-tionwasdifficult,givingtheattackertheadvantageofsurprise.Toshootdownanattackingaircraft,otheraircraftorguncrewshadtoprevailintheengagementandassureaprobabilityofkill,allinarelativelyshortspaceoftime. But the survivability duel was about to change beyondrecognition.InBritain,by1937,scientistshaddevelopedade-vicetodetectaircraftatrangesfarbeyondthatofthehumaneye.Theeffectonairtacticsandoperational-levelplanswouldshapemostofthedecisivecampaignsofWorldWarIIandthedynamicsofaircombatfortheremainderofthecentury.

THE RADAR GAME BEGINS


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gameforeverchangedaircombattactics,anditseffectonsur-vivabilityratesrapidlycametodominateoperationalplansforairwarfare. Radartookairmenbysurprise.Whilethebasicprinci-plesbehindradarwaveshadbeenunderstoodbyatleastafewscientistsforyears,itwasnotuntilthemid-1930sthatintensiveresearchsolvedseveralimportanttechnicalchal-lenges. In1904, justoneyearafter thefirst flightatKittyHawk,aGermanengineernamedChristianHulsmeyerinventedthefirsttelemobiloscope.Thedevicegeneratedradiowavestodetectshipsatrangesofafewmiles.Hulsmeyerobtainedapatentforhisinventionbutfailedtofindcustomersforhisdevice,andthepatentslapsed.But30yearslater,in1934,researchersinAmer-ica, Britain, France, Italy, Germany, and the Soviet Union wereatworkonradardetectionprojects.TheLeningradElectrophys-icsInstitutehadadevicetodetectaircrafttwomilesaway.TheFrench luxury linerNormandieboastedamicrowaveobstacledetector. The British brought together a research team that hadthefirstsuccessinusingradiowavestofindtherange,azimuth,andheightofanaircraft.Inthesummerof1935,RobertWatson-Watt’sexperimentsatOrfordnessdetectedandtrackedaircraftatarangeof40milesandmeasuredheighttowithin1,000feet.RadioDirectionAndRanging,betterknownbyitsnicknamera-dar,hadbeenborn.

How Radar Works Why were aircraft so vulnerable to radar detection? Inshort,forallthereasonsthatincreasedtheiraerodynamicquali-tiesandperformance.Metalskins,largeverticalcontrolsurfac-es,bigpowerfulengineswithmassivepropellerblades:All thefeaturesthatmadetheGermanMe-109MesserschmittandtheAmericanBoeingB-17bomberfasterandmorereli-ablealsomadethemexcellentradarreflectors. Radar detects scattered radiation from ob-jects,and isparticularlygoodatdetectinghighlyreflectivemetallicobjectsagainsta less reflectivebackgroundsuchastheseaorthesky.Wavesaregeneratedandtransmittedintheradio-frequencypartof theelectro-magnetic spectrum.The radarreceiverthencapturesthereflectionofthewavesastheyareencounteredandaretransmittedbackfrom objects of interest. Since the speed of radiowavepropagationfromtheradarisaknowncon-stant, radar systems can determine the position,velocity,andothercharacteristicsofanobjectbyanalysisofveryhighfrequencyradiowavesreflect-edfromitssurfaces. Hulsmeyer was readily able to develop andpatentaradardetectiondevicein1904becausetheprinciplesofelectromagneticwaveshadbeenthoroughlyresearchedinthelatterpartofthe19th

century. An electromagnetic wave consists of two parts: anelectricfieldandamagneticfield.Thesefieldsrapidlyfluctuateinstrength, risingtoapeak, fallingawaytozero, thenrisingtoapeakagain.Thisprocess repeats itselfoverandoveras thewavetravels(propagates) inadirectionatrightanglestotheelectricandmagneticfields.Wavesaremeasured in termsoffrequencyandwavelength. The frequency of a wave equals the number of crestsortroughsthatpassagivenfixedpointperunitoftime.Wavefrequenciesaremeasured in termsofkilohertz (onethousandcyclespersecond),megahertz(onemillioncyclespersecond),andgigahertz(onebillioncyclespersecond).Wavelength,thedistancebetweentwosuccessivepeaksofthewave,isdirectlyrelatedtothephysicalsizeoftheantenna. Increasingthefre-quencyofawavedecreasesthewavelength. British experiments with the first operational detection ofaircraftessentially sought to swapanairplane fora radioan-tennatotransmitbackasignal.Tograspthisprocess,itisimpor-tant tounderstand that radarenergy strikinganaircraftdoesnotsimplybounceoffthetargetinthewaythataballbounceswhen itstrikesawall.Whenaradarwavemeetsanelectricalconductor,suchasawire,itcreateswithinthatelectricalcon-ductorelectromagneticcurrentsatthesamefrequencyasthewave.Theelectricandmagneticfieldsthatformthewavearepolarizedandretransmitted.Thisretransmissionisthesamethingthatoccurswhenlistenerstuneintoradiosignalsusingaradioreceiverandantenna. Panel1showshowelectromagneticwavesfromadistanttransmitterattheradiostationinduceasmallcurrentwithintheantennaoftheradio.Theradioreceiveramplifies itandtrans-mitsitthroughthespeakers. Panel2showsthatwhenaradarwavehitsanaircraft,itinduceswithintheaircraftelectricandmagneticcurrents.

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Thesecurrentsthencreatenewelectro-magnetic waves, depicted in Panel 3,thatareemittedfromtheaircraftinvari-ousdirectionsand,dependingonwheretheystriketheaircraft,areseenbythera-darreceiverasreflectedechoes.Theseechoesaresignificantlyweakerthantheoriginal electromagnetic waves trans-mittedbytheradar. Thefirst testofBritish radar—theDa-ventry Experiment—was conducted onFeb.26,1935.Inessence,theDaventryex-periment treated the aircraft like a flyingantenna that could transmit waves backto the receiver on the ground for detec-tion. Watson-Watt’s team carefully cali-brated the wavelength of the transmit-tedsignalsothattheaircraftwingwouldgenerate a strong return. British scientistsknew from their work on radio antennaethat a wire whose length correspondedtohalfthewavelengthoftheradiosignalwouldre-radiatestrongly.Assumingthatthewingofanaircraftwouldbehaveinthesamemanner,theengineerssettledonafrequencywhosewavelengthwouldbetwicethatofthetypi-calGermanbomber,orabout25meters(80feet).Thustheen-gineerschose49-meterwavelengthsignalsat6MHz. ABBCradiostationservedasacrudetransmitterissuingaconstantbeamatawavelengthof49meters.AHeyfordbomb-er,flyingat100mphand10,000feet,eightmilesdistant,crossedthe continuous beam and briefly transmitted reflected radiowavesbacktothereceiver. One initial problem withWatson-Watt’s Daventry contin-uous-wave radar system was that outgoing signals interferedwithincomingsignals.ByJune1935,theBritishhaddevelopedapulsedtransmitter,whichsentoutpulsesofelectromagneticenergy so that the receiver could distinguish among echoes.Pulseradar,nowstandard,usesasingleantennafortransmissionandreception.Pulse radarsendsahigh-powerburstof radia-tionthenwaitsforthereturnsignal.Theintervalbetweenpulsesmatchesthetimeforawavetoreachatargetatagivendis-tance.Thisprocesstakesplacethousandsoftimespersecondinatypicalpulseradar. Uponseeingtheblipappearonacathoderaytube,Wat-son-Watt reportedlycommentedthatBritainhadbecomeanislandoncemore.Theprospectofdetectingaircraftenroutetoattackopenedupprofoundpossibilitiesforairdefenders.Britainrushedtocapitalizeonthem. ByApril1937,experimentalstationshaddetectedplanesatarangeof100miles,andbyAugust,BritainhadactivateditsfirstthreeChainHomeradarstationsatBawdsey,Canewdown,andDover.

Radar Early Warning: The Battle of Britain TheairplanesrollingofffactoryassemblylinesontheeveofWorldWarIIwerepoorlypreparedtocopewithradaranditsconsequences.Planesflewfaster,higher,andfarther,withgreat-ersafetyandreliability,thantheyhadinWorldWarI.Theyhadsturdymetalskinsandbigenginesthatgeneratedthousandsofhorsepower.However,intheradargame,aerodynamicadvan-tages also contributed to the prospect of being detected, inadvance,byradar.Theradargamestrippedawaytheelementofsurprisethatdatedfromthedaysofvisualandacousticde-tection.Itaddedanewandcomplexrealmofvulnerabilityandopportunitytotheaerialduelandmadethedetectionstageoftheduelcriticallyimportant. Britishairdefenseswerethefirsttoscorebigbenefitsfromtheradargame.TheChainHomeradarsystemnowringedtheairapproachestotheisland. DuringtheBattleofBritainin1940,radarearlywarningal-lowedtheRAFtodirecttheirscarcefighterstoattackincomingGerman formations instead of patrolling assigned air defensesectors.InearlyAugust1940theLuftwaffestillbelievedthatRAFfighters were“controlled from the ground” and“tied to theirrespectivegroundstationsandaretherebyrestrictedinmobil-ity....Consequently,theassemblyofstrongfighterforcesatde-terminedpointsandat shortnotice isnot toheexpected.” 17

TheLuftwaffejudgedthattheRAFwasalreadyweakenedandcouldbedefeatedindaylightoperationsbypiercingthinsec-tordefenseswithstrongerformationsastheRAFattemptedtopatroleverysectorofthesoutheastcoast. Instead, the RAF found that radar early warning madefighters effective in a way that had not been imagined. The


18

ChainHomeradarearlywarningsystemdetectedapproachingaircraftouttoabout100miles.Radarinterceptspassedtosec-toroperationscentersalertedtheRAFgroundcontrollerswhentheGermanstookofffromtheairfieldsacrosstheChannelandformedupforattack.EarlywarninggavetheRAFamuchbet-terestimateof theheadingandnumbersofGermanaircraft.Updatedestimatesof thebearingof the incomingformationscluedintheRAFastotheobjectivesoftheattack.Missiondi-rectorsonthegroundcouldthenalertfighterstoscramble,orevenbetter,vectorfightersalreadyonpatrolandataltitudetointercepttheGermanformations. Admittedly, theLuftwaffe’sstrategycountedonbring-ing the RAF up to fight. But the RAF’s advantage in beingabletomassfortheencountersrobbedtheGermansofsur-priseanditsadvantages,suchasselectionofthetimeandlocationforaerialengagement.Radarhelpedcompensatefor inferiority in numbers in a way that would never havebeenpossiblehadtheRAFtriedthekindofsectordefensetheGermansanticipated. TheBattleofBritainshowedthatearlywarninggavede-fendingfightersthetimeandflexibilitytomassforintercepts.FortheRAF,theflexibilityprovidedbyradarstoletheadvantagesofmassfromtheLuftwaffe.Bymid-September1940,theGermansdidnotbelievetheyhadestablishedevenlocalairsuperiorityover the southeast of England and the Channel coast. With-outairsuperiorityintheseareas,theamphibiousinvasionplancode-namedOperationSealioncouldnotbemounted.Inthe

end,thefailuretogainairsuperioritycompelledtheGermanstopostponetheinvasionofBritainindefinitely.

Survivability and Air Operations Thesurvivabilityduelnowdependedmuchmoreonmak-inguseofearlywarninganddetection. JustasearlywarningradargavetheBritishanedgeintheBattleofBritain,itgavetheGermansanadvantagewhentheAlliesbegandeeppenetra-tionattacksontargetsinNazi-heldEurope. Bombersurvivabilitybecamethefirstkeytooffensiveac-tionintheairandtothedesignoftheEuropeantheatercam-paign. What is seldom realized is that the Eighth Air Force’smost legendary—and most costly—missions in 1943 focusedonwinningcontroloftheair.EighthAirForce’sobjectiveswerenotbasedprimarilyonastrategiccampaignthatdisregardedcombinedarmsstrategyintheEuropeanTheaterofOperations(ETO.) Instead, theyhadasingleoverridingaim: tochoke theLuftwaffe.Allotherprioritiesweresubordinate. In June 1943, the Combined Chiefs of Staff ordered thebombing campaign to concentrate on the German aircraftindustry. InthePointblankdirective,theycalledontheairarmto“checkthegrowthandreducethestrengthofthedayandnightfighterforces.”The“firstpriorityoftheBritishandAmericanbombersbasedintheUnitedKingdomistobeaccordedtotheattackofGermanfighterforcesandtheindustryonwhichtheydepend.”AsanArmyAirForcesreportlaterputit,“thesuccessoffuturestrategiccampaignsandinvasionofthecontinentde-

pendedoneliminatingtheLuftwaffe.”18

GermanearlywarningradarsliketheFreyaringedthecoastofNazi-occupiedEu-rope. Radar tracking allowed the Germanstoorganizeanairdefensethatwoulddirectfightersatforwardbasestoengagebomberformations.Thedeeper thebombershad toflytoreachtheirtargets,themoretimeGer-man fighters would have to engage them.This greatly increased what can be termedthe time in jeopardy for attacking bomberformations.Timeinjeopardyisdefinedinthisstudyas theperiodduringwhichdefenderscould track and engage attacking aircraft.Instead of being intercepted only over thetarget area, bombers might be repeatedlydetectedandengagedontheirroutetothetargetandback. The Allies rapidly discovered thatattacks on cities deep in Europe exposedthe formations to repeated engagementsstagedoutofthemanyLuftwaffebasesfromtheFrenchandDutchcoasts to the interior.Radartrackingmadethispossiblebyalertingfightersandleadingthemtothegeneral lo-cationofthebomberformations.

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ThePointblankdirectivepresentedAlliedbomberswithsignificantsurvivabilityproblemsbecause German air defenses were muchmoreeffectivewith theuseof radar.TheonlywaytostrikeattheLuftwaffewastohititsfight-erproduction.Germanfighterproductionwasconcentratedatafewmainindustrialcenters. EighthAirForcedecidedtopairaraidonRegensburg, which produced 500 of the esti-mated650Me-109sthatrolledofftheassemblylineseachmonth,withastrikeonSchweinfurt’sball-bearingsindustry. The Regensburg force left the coast ofEnglandat0935onAug.17,1943.Germanearlywarning radars firstdetected thebomber for-mationsastheyclimbedtoaltitudeandformedupoverEngland.At17,000feet,theformationwasalreadywithinrangeoftheGermanradarscreenwithits150-milerange.GermanairfieldsfromParistoDenmarkalertedfighterstointer-ceptthebomberstreams. Enroutetothetarget,thebombersspentnearly all of the next three hours in jeopardyfrom fighter intercepts along their radar-tracked flight path.Ground controllers passed the location and bearing of thebomber formations to the fighters. German fighters acquiredthebombersvisuallyandusedelectricgunsightstotrackandattack them.As theB-17sapproached the target,antiaircraftguns,alsocuedandvectoredbyradar,putupadensecurtainof88mmflak.LeadformationsbombedRegensburgat1143.TheSchweinfurt force,delayedby fog,departedEnglandat1314andspentthenextfourhoursinjeopardy,bombingat1457. FortheB-17,theengagementphaseofthedueldepend-edontheformation’sdefensivefirepowerandlater,onescortfighterstodefendthebombersagainstengagementbyenemyfighters.Whentheformationreachedthetargetarea,morede-fensesawaited. Bombers had to fly directly over their targets to releasetheir bomb loads. Some targets, like the oil refinery at Leuna,wereringedwithover700antiaircraftartillery(AAA)batteries.

Ground-basedflakbatteriesmadeuseofradarfortargettrackingandheightfinding.From1941,Germanunitsintroducedgunlaying radar. Ground-based fire control radars aided theGerman antiaircraft guns in determining height and bearing.Withaccurateheightestimates,fusesonartilleryshellscouldbesettoexplodenearerthebomberformations.Overthecourseof the war, German air defenses also experimented with ra-dar-guidedflakrockets. The Regensburg force flew on to land at bases in NorthAfrica.TheroutewaspickedtoavoidAAAandfightersonthereturn route.TheSchweinfurt force returned toEnglandalongthe same route, spendinganother threehours in jeopardy.Alltold, Eighth Air Force lost 16 percent of the dispatched forcethatday. In thefinalanalysis, the ruggeddesignof theB-17oftenhelpedthebomberanditscrewsurviveattackbydecreasingthe probability of kill. The chart below diagrams a typical en-


20

gagementagainstunescortedbombers.Ondeepraids,bomb-erformationswithstoodnumerousassaultsfromfighters.Withtheadvantage tilting toward the fighters, EighthAir Force had todeviseadditionaltacticstowinairsuperiority. An integrated air defense that employed radar for earlywarning and tracking could inflict losses on the attackers thatcompoundedovertime.Asustainedlossratecomparabletotherateof16percentontheSchweinfurtandRegensburgraidswouldhaverippedthebomberforceinhalfafterfivedays.Intwoweeksofcontinuousoperations,theforcewouldhavebeendrainedtolessthan20percentof itsstartingstrength.Thelossofmachinespalednexttotheloss,injury,andcaptureoftrainedaircrews.Aver-agelossesin1943puttheArmyAirForcesontracktoconsumeitsentireforceatarateoftwo-and-a-halftimesperyear. With radar providing highly controlled intercepts, thebomberformationswerespendingtoomuchtimeinjeopardy,subjecttoorganizedandpersistentattackinsteadofsporadicencounters—conditionsthataircraftdesignersofthemid-1930shad not anticipated. Since the tactics of formation flying didnotcompensateadequately,theadditionalmeasureoffighterescortswithlongerrangemadeupthegap,ensuringthatthebombersspentlesstimeinjeopardyoneachmission. Whatthefightersneededtodotohelpthebomberssur-vivewastoextendtheirrangeandtotaketheoffensive.Lugerdroptanksmetthefirstgoalin1944.Bysweepingaheadofthebomberformations,fightersregainedtheadvantagesofinitia-tiveandposition.JimmyDoolittle,whotookcommandofEighthAirForceinlate1943,laterrelatedthatontakingcommandhespottedasignsayingthemissionofthefighterswastobringthebombersbacksafely.Doolittleordereditchangedtoread:“Thefirst duty of the EighthAir Force fighters is to destroy Germanfighters.”19

Luftwaffe fighter ace and commander Gen. Adolf Gal-landwroteafterthewarthatthedaytheEighthAirForcefight-ers went on the offensive was the day the Germans lost thewar.Theduelbetweenbombers,escorts,andLuftwaffefightersturned inpartonwhodevised thequickest remedies forair-craftsurvivability,andinpartonproductionofaircraft.FortheAllies, escort tactics curtailed losses and destroyed Germanaircraft,bringingattritionratestolevelsthatcouldbemetbywartimeproduction.FortheGermans,thecrucialsurvivability

factorsultimatelycamedowntothelossoftheirtrainedandexperiencedpilots.

Deception Techniques Another clear example of radar’s impact was the Ger-man development of night intercept operations.After the fallof France inMay1940, theRAFhadbegunnightbomberat-tacksonGermanmilitaryandindustrytargets intheRuhrandelsewhere.Germanearlywarning radarcouldstillpickup for-mations on their approach but the problem of visual acquisi-tionandtrackingwasmuchmoredifficulttoperformatnight.However,findinggroundtargetsatnightwasalsomuchmoredifficult. A 1941 report found that only one in five RAF sortiesdroppedbombswithinfivemilesofthetarget.BritishPrimeMin-isterWinstonChurchillorderedhighprioritydevelopmentofra-daraidsfornavigationtoimproveaccuracy.Byearly1942,radarnavigational devices were being installed in heavy bombers.ThehighperformanceH2Ssystemwasavailableonanumberofaircraftbymid-1943,andonJuly24,H2Spathfindersleda740aircraftattackonHamburg. TheGermanscounteredthesefarmoredevastatingnightraidsbyperfectingasystemofground-controllednightfighterinterception thatalsocapitalizedon radar.TheGermannightinterceptoperations linkedradarearlywarningtoasystemofground control and led also to the use of airborne radar forfighterintercepts. Asshowninthefourpanelsofthechartabove,earlywarn-ingfirstcuednightfighterstotakeoffandclimbto20,000feet,wheretheytookupstationonaradiobeacon,awaitinginstruc-tions. When bombers entered the radar range of a groundstation,Germancontrollersvectorednightfighters toan inter-ceptcourse.Onceoncourse,pilots reliedonvisualdetectionandeventhebuffetingofwaketurbulencetofindthebomb-er streams. Night fighter pilots radioed back the position andheadingofthebomberstreams,thenwereclearedtoengage. Duringtheengagement,nightfightersusedspecialmodifi-cationssuchasupward-pointinggunsandshort-rangeairborneradar.Theyalsoemployedairborneradarwitharangeofaboutfourmilestodetectthebomberstream. On the night of March 30, 1944, German night fighters

21


broughtdown107Britishheavybombers intheirraidonNurn-berg.Attheirpeak,Germannightfighterspracticed“themostcomplextypeofmodernaerialcombat,”inthewordsofanof-ficialAmericanAAFaccount.TheairborneradarsofWorldWarIIhadnotyetevolvedtothepointwheretheycouldprovidepre-cisefirecontroltoguideactualweaponstotheirtargets.How-ever,theincreasingexactnessofradar-controlledinterceptwasdeadly enough to spur development of measures to preventradardetection.

Early ECM Radarbegatcountermeasuresalmostimmediately.Asra-dar began to give air defenders a clear picture of the loca-tion,direction,andaltitudeofincomingattackers,theattackerssoughtwaystodenythisinformationtotheenemy.Earlycoun-termeasuresprimarilyaffectedthevariablesofdetectionandengagementinthesurvivabilityequation. Manipulatingtheelectromagneticspectrumthroughcre-ating deceptive returns took three forms: generating clutter,jamming transmissions, and making objects appear larger toconfusecontrollers.Allwerepioneered in some form inWorldWarII. Generating false signals sought to neutralize the earlywarningradarthatformedthebackboneoftheGermannightfighterinterceptsystem.InaFebruary1942commandoraidatBruneval,theBritishseizedaWurzburgradarsetwhichaidedinthedevelopmentofcountermeasures.Theproductwas“Win-dow,” the codename for strips of metallic foil dropped frombomberstosaturateenemyradarscopes. Chaffcomplicated thegroundcontroller’s jobbycreat-

ingnumerous flashesand falseblipsandcloudson the radarscreen. Although countermeasures were developed swiftly, theRAFwaitednearly18monthstousetheminbattle.Seniorplan-ners feared that if the RAF employed countermeasures, theGermanswoulddothesame.20IntheJuly1943Hamburgraids,theRAFused92millionstripsofWindow,whichbroughtGermanradarscopesalivewithfalseechoes.TheRAFlostonly12aircraftratherthanwhatwouldhavestatisticallybeenaround50with-outtheaidofWindow.21

GermanairdefenseswerethrownintodisarraybytheRAFtactics.AccordingtotheLuftwaffe’sGalland:

“Not one radar instrument of our defense had worked. The Brit‑ish employed for the first time the so‑called Laminetta method [Window]. It was as primitive as it was effective. The bomber units and all accompanying aircraft dropped bundles of tin foil in large quantities, of a length and width attuned to our radar wave length. Drifting in the wind, they dropped slowly to the ground, forming a wall which could not be penetrated by the radar rays. Instead of being reflected by the enemy’s aircraft they were now reflected by this sort of fog bank, and the radar screen was simply blocked by their quantity. The air situation was veiled as in a fog. The system of fighter direction based on ra‑dar was out of action. Even the radar sets of our fighters were blinded. The flak could obtain no picture of the air situation. The radar target‑finders were out of action. At one blow the night was again as impregnable as it had been before the radar eye was invented.”22

German counter-counter-measures followed rapidly. Skill-ful operators learned to sort outfalse signals and maintain theabilitytoprovidevectors.TheLuft-waffe engaged 4,000 engineersonprojectssuchastheWurzlauswhich detected the slight differ-encebetweenslow-movingstripsof foilandthebombersflyingat200mph. Other devices tried topinpoint the faint radarmodula-tionpresentonechoes fromair-craft propellers. A set of specialreceiving stationswasequippedto detect transmission from theBritishH2Snavigationradarsets. In the air, German nightfighters switched to three-meterwavelength (90 MHz) radar thatwas unaffected by the Windowstrips that had been cut for 50centimeterradar.23SomeGerman


22

fighters could also detect emissions from the British H2S systemon the pathfinders and a later tail-warning radar. The FuG 227Flensburgradarreceiverwastunedtomatchthefrequencyofthe“Monica”tail-warningradarsetsusedbyRAFbombers.TheFuG350NaxosperformedthesamerolebutwastunedtotheH2Sradarset.TheBritishlearnedoftheseGermandevicesinearly1944whenaJu-88GnightfightermistakenlylandedinEssex. Within10daysoffindingthisaircraft,theBritishdevelopedlonger forms of Window (code-named“Rope”), removed tailwarningradarsetsfrombombers,andorderedbombercrewstouseH2Sonlywhenabsolutelynecessary. AsecondmajorECMdeviceusedinthewar,codenamed“Carpet,” electronically jammed German radar. In October1943,theAlliesfirstusedCarpetasbothabroadband(multiplefrequencies)andspotjammer(singlefrequency).Theideabe-hindjammingwastotransmitsignalsonthesamefrequencyastheradarreceiversothattheoperatorcouldnotsortoutthera-darreturntheysoughtfromsignalssentbythejammingaircraft.TheAlliesusedCarpet,Dina,Rug,Lighthouse,andotherjammersthat were effective in the frequency ranges of most Germanradarsystems.24“Mandrel”jammingaircraftaccompaniedRAFbombers todisruptFreyaradarsets,“Piperack”counteredtheLichtenstein radar, and“Perfectos” triggered German fightersidentificationfriendorfoe(IFF)setstorevealtheirposition. Finally, theBritishexperimentedwithways toblanket thesky with large radar returns that would mimic a large attackforcewherenonewaspresent.“Moonshine”transpondersemit-tedsignalsthatmadeasingledecoyaircraftappearonradarasalargeformationofbombers.Toobtainthenecessaryradioand radar frequencies for these devices, the British sent“fer-ret”aircraftofthesecret192and214RadioCounterMeasuresSquadronalongsidebombingmissionstousesophisticatedre-ceiverstodetectenemytransmissions.25

TwoelectronicarmadaswerepartofthecastfortheNor-mandylandingsonJune6,1944.Asmanyas600radarandjam-ming systems guarded the coastline. Just before the invasion,Allied bombers destroyed key German jamming sites and hitradar installations, leavingasitenearLeHavredamagedbutfunctionalaspartoftheruse.ThentheAlliesprojectedtwofalseinvasionforces,knownasTaxableandGlimmer,byemployingamenagerieofforcestoformlargeradarreflectors. TaxableconsistedofaformationofeightLancasterbomb-ers flying in a pattern dispensing chaff to make the GermansthinkalargeinvasionforcewasheadedtowardCapd’Antifer.TheLancasterswereequippedwith“Moonshine”transpondersthatpickedupGermanradarimpulsesandamplifiedthemtodepictalargerforce.Belowtheaircraft,aflotillaofboatstowednavalbarrageballoonsequippedwithradarreflectorsdesignedtomakethemlooklikelargewarshipsandtrooptransports.TheGlimmerforcemademockrunsagainstDunkirkandBoulogneandusedjammingtoconcealthetruesizeoftheforce.ShipsintheGlimmergroupbroadcastnoisesimulatinganchordrops,and smoke screens concealed operations. Meanwhile, RAF

bombersdroppedhugeamountsofWindowfartothewestoftheinvasionsite.26

Radarcountermeasureshelpedpreservetacticalsurprisefor the invasion force. In theend,onlyoneGerman radar sitepicked up the actual invasion force, and that station’s reportwaslostinthechaosoffalsereportsgeneratedbydetectionsofTaxableandGlimmer.27

The Radar Game and the Theater Campaign Theaircomponentdirectlyaffected the timetableofplanningfortheater leveloperationsthroughoutWorldWarII.Attheoperationallevel,controloftheairwasaprerequi-siteforsuccessfulgroundoperations.InWorldWarIIasneverbefore, the air components set the parameters of theatermilitarystrategyforeachbelligerent.Onehistorianwroteoftheimportanceoftheairoperations intheBattleofBritainand how they were intended to precede a cross-channelinvasion:

“In previous campaigns, the aerial onslaught against the enemy air forces had taken place simultaneously with the army’s advance across the border: for Operation Sealion, it was to be a precondition to military action.”28

SurvivabilityandtheroleoftheaircomponentwasnolessimportantastheAlliestooktheoffensive. Seen in the light of operational planning, survivabilityhadtobeachievedeveninthefaceofaradargamethattookawaytheattacker’selementof surprise.TheRAFandAAFwoncontroloftheskiesoverEurope,albeitatgreatcost.Thepayoff,aslongexpected,wasthefreedomtoconductattackstoshapeandsupporttheNormandylandings.

Survivability and the Theater Campaign: Operation Overlord LandingforcesonthecoastofFrancewasastraightfor-wardbutambitioustask:“Pourmenandequipmentashoreat one or more points so fast that they could overwhelmtheenemydefensesthere,thendiginfirmlytoavoidbeingthrownbackintotheseabythefirstenemycounterattack.”JustastheGermansneededlocalairsuperioritytoattemptSealion, the Allies had to eliminate the Luftwaffe from thebattleareabeforetheinvasion. Thereasonwasfirmlyrootedintheoperationaldoctrinethat had guided plans for the invasion all along. Germanforces in the Normandy region numbered nearly one mil-lion.TheAllieswouldputashorealmost325,000troopswithindaysafterD-Day.However, thenumericalsuperiorityof theGermans had to be offset by denying Field Marshall ErwinRommeltheabilitytoreinforceandmaneuvertodefeattheinvasionforce’stoeholdonthecontinent. Whenaircraftwereassuredofareasonablelevelofsur-vivability,theycouldbecountedontoexecutemissionswith

23


“[I]n an all‑weather Air Force, radar must be the universally used tool for bombing, gunfire, naviga‑tion, landing, and control. … The development and perfection of radar and the techniques for using it effectively are as important as the development of the jet‑propelled plane.”—Theodor von Kármán, August 1945

Developments inguidedmissile technology,combinedwith additional improvements to radar detection, wouldmake the postwar radar game even more deadly. By the1960s,radar’sabilitytoguideeachphaseofthesurvivabilityduelwouldthreatentocurtailtheabilityofaircrafttocontroltheskiesoverthebattlespace. Research on guided missiles had begun during World

directimpactonenemygroundforces.AirsuperioritygaveGen.DwightD.EisenhowertheabilitytoeventhebalanceofgroundforcesintheNormandyregion.Alliedairguardedfriendly forces fromattack,whilegoingon theoffensive toshapethebattlebehindthefrontlines.Airattacksonbridges,roads,andrail transportationpreventedtheGermansfrommovinginreinforcements.Alliedairpowerkepttheroadandrailtransportsystemunderconstantattack.Motortransportmovedonlybynightandeventhenunderbombardment.“Railtransportisimpossiblebecausethetrainsareobservedandattacked in shortorder,” recordedGen. FriedrichDoll-manoftheSeventhArmyHighCommandonJune11,1944.Dollmanwentontoreport:

“Troop movements and all supply traffic by rail to the army sector must be considered as completely cut off. The fact that traffic on the front and in rear areas is under constant attack from Allied air power has led to delays and unavoid‑able losses in vehicles, which in turn have led to a restriction in the mobility of the numerous Panzer units due to the lack of fuel and the unreliability of the ammunition supply.”29

Theeffectsaccumulated,forroadtransportwaslessef-ficientthanrailtransport,androadtransportitselfwasmorecostly because of strategic shortages of rubber tires andpetrol.30

Airinterdictionrestrictedtheenemy’sabilitytoresupply,reinforceandmassforamajorcounterattack,therebyassist-ingtheAlliesastheypressedonwiththeliberationofEurope.The lackofaconcertedchallenge from the Luftwaffeen-abledfreedomofoperationintheskiesoverNormandythat

allowedthetacticalairforcestocontroltheflowofenemyforcesbehindthefrontlines.

In Summary The course of the air war over Europe indicated thatsurvivabilitywasafleetingbalanceofelementsandthatitscomponents could change as different tactics, technolo-gies,andobjectiveswererolledintotheequation.Hadanyof the belligerents introduced their advanced aircraft de-signsinsignificantnumbers,andattherighttime,theymighthavetippedthebalanceoftheairwarbyagainalteringtheequationofaircraftsurvivability.TheMe-262“easilyflewcir-clesaroundourbestfighters,”admittedDoolittle,whoafterthewarremarked,“Ishuddertothinkoftheconsequenceshad the Luftwaffe possessed this aircraft in large numbersandemployeditproperly.” TheradargameofWorldWarIIopenedaneweraofaircombat.Forthefirsttime,aircraftsurvivabilitywasama-jorvariableintheateroperationalplans.Theduelforsurviv-abilitywasnowdominatedbyradarinthedetectionphase.Thesetwochangescameatatimewhencombinedarmsoperationsstartedtodependontheaircomponenttosettheconditions formajorgroundactionand toensure thatattacking forceson thegroundcouldcountonnotbeingstoppedbyenemyair. WorldWarIIalsomarkedcleartrendsthatwouldcon-tinue to alter the duel between attackers and defenders.Experiments with airborne radar in fighters, and with ra-dar-controlledflakandmissiles,indicatedthattheengage-mentphaseandprobabilityofkillwouldsoonbecomepartofradargame,too.

THE POSTWAR RADAR GAMEWarII.TheGermanEnziansurface-to-airmissilewasjustoneofseveralexperiments. Postwarresearch,especiallyintheUnitedStatesandtheSovietUnion,concentratedonguidingmissiles throughon-boardradarorinfraredseekerstoimproveaccuracy.NATOintelligencefirstdiscoveredtheexistenceoftheSovietSA-2in1953.31ThefirstAmericansurface-to-airmissilebecameop-erationalinthesameyear. BoththeUSandtheSovietUnionenvisionedaneedforair defenses to guard their territory from attacking bomb-ers carrying nuclear weapons. An early US missile namedBomarcreliedonaground-controlledradartoturnthemis-sile into attack position. A second radar guidance systemwouldallowtheMach2.7Bomarctolockontoitstargetinflight.32Vast quantities of these radar-guided SAMs with at


24

for“parasite”fighterstobelaunchedfromandrecoveredbybombersthemselveshadproved impractical.Thebomberswould have to approach their targets in the USSR withoutescort.AttackinginnumberswouldalsocomplicatetheSo-vietdefenseproblem.BythetimetheB-52wentintoproduc-tion in 1952, Gen. Curtis LeMay knew that the big bomberwould be conspicuous on radar, but reasoned that its sizewouldeventuallypermitittocarrymoreelectronicgearforradar-jamming.35Besides,SACwasnotnecessarilyposturingfor a sustained offensive. Talk of one-way missions and theknock-out blow of the atomic bomber offensive eclipsedthe calculation of long-term bomber attrition. Still, the factremainedthattheSovietUnionwasdevelopinglongrangeearlywarningradarsandradar-controlledSAMstoengagehostileaircraft. The severity of this threat stood out clearly in a state-mentbyGen.ThomasD.White. Insummer1957, justbeforebecomingUSAFChiefofStaff,Whitestatedthatamixofbal-listicmissilesandbombersinthenuclearfleetwould“permitgreaterversatilityforourforcesbyrelievingmannedbomb-ersofthoseheavilydefendedtargetswherethecostofat-tackingwithbomberswouldbetoohighandwherepreciseaccuracyisnotmandatory.”36Itwasaroundthistime,though,thatspeculationblossomedthatcontinueddevelopmentofradar-guidedmissileswouldusher in“thecomingdeathoftheflyingairforce.37

On the Verge: The U‑2 and SR‑71 Meeting the challenge of integrated radar-controlledairdefensesequippedwithradar-guidedSAMsbecamethechiefpreoccupationofstrategicairwarplannersinthelate1950sand1960s.Aircraftdesignwaspushingthelimitsofhighspeedandhighaltitudeflight,andforatime,thesetwoar-easbecamethenaturalresourcesfornewsurvivabilitytech-niques. Newreconnaissanceaircraftstroveformaximumsurviv-abilitybecausetheirmissionwastooverflytheSovietUnion.Onlyextremecombinationsofperformanceattributescouldkeepaircraftoutof jeopardy.Onetacticwastoflyathigh

leasta25-milerangewouldberequiredtodefendcontinen-talUSairspace.Thegrowingthreatfromradar-controlledmis-sileswasputtingaircraftsurvivabilityintosomedoubt.Radarand infraredseekerscouldguidemissilesmostorallof thewaytothetarget.Radarnowplayedaroleineachstageoftheduel:detection,engagement,andprobabilityofkill. USplannerswerealsowellawarethattheSovietUnionwasbeginningtopresentmoreheavilydefendedtargetstoSAC’sbombers. In1947,discussionsonrequirementsfortheXB-52staredthesedilemmasintheface.Togainmorepay-load,anatomicbomber“mightevenhavetodispensewithguns and armor in order to attain the speed and altitudenecessary to assure its survival.”33 The lack of intelligenceabout threats to be faced over the Soviet Union createdmore complications. An air weapons development boardraisedquestions:

“Would it be possible for them to fly fast enough and high enough to evade the interceptors? Or would they still need to bristle with guns? If the latter were true, development be‑came more complex. Bulky turrets had to be eliminated for aerodynamic reasons, while fire control systems had to cope with high speeds.”

To cap off the dilemma, if enemy fighters had flexibleguns,speedwouldnotyieldadequateprotection.34

The options for countering radar-guided missiles andantiaircraft fire started with traditional improvements, incategories like speed and performance. Mastering jet en-ginesandmakingtheearly jetaircraftsaferandmorereli-ableconsumedtheattentionofaircraftdesigners.Jetfight-erswerejudgedonthesamegeneralperformancecriteriaas were the Spads ofWorldWar I: speed, maneuverability,power,andoverallperformance.Aircraftofthejetagehadgreatly improved performance, but their conventional de-signsremainedjustaseasyforradartospot. Thebombersthatenteredtheforce inthe1950sreliedonaltitude,speed,andatailgunner’sposition.TheB-47,forexample,hadatopspeedofmorethan500knots.Concepts

25


altitude.Builtin1955,theU-2aimedtoflyabovethealtitudeceilingofSovietfighter-interceptors.TheSovietsknewaboutthe U-2 flights from the start. As one of the early pilots re-called:

“I knew from being briefed by the two other guys who flew these missions ahead of me to expect a lot of Soviet air ac‑tivity. Those bastards tracked me from the minute I took off, which was an unpleasant surprise. We thought we would be invisible to their radar at such heights. No dice.”38

Then on May 1, 1960, a barrage of 14 SA-2s broughtdowntheU-2pilotedbyGaryFrancisPowers.ItwasthefirstUSaircraftlosttoaradar-guidedSAM.AnotherU-2wasshotdown in 1962.With the altitude sanctuary pierced, aircraftdesignwouldhavetopresstonewextremestoprevailintheradargame. Tocopewiththeseairdefenses,theSR-71combinedanoperationalceilingof80,000feetormorewithatopspeedof Mach 3+ to enhance survivability on deep penetratingreconnaissancemissions. TheSR-71wasequippedwithECMtojammissileseekers,and itsdesignprobedat thepossibilityofminimizing radarcross section. However, its chief survivability characteristicswerealtitudeandspeed.SAMsfiredat theSR-71oftenex-plodedseveralmilesbehindthestreakingaircraft.“Weknewwe’dprobablygetshotat,butitwasn’tabigworrybecauseatourheightanSA-2missilesimplydidn’thavetheaerody-namic capability to maneuver,” one SR-71 crew memberreasoned.39TheattempttobuildabomberintheleagueoftheSR-71 failedwith theB-70.Lt.Gen.OttoJ.Glasser,chiefofstaffforresearchanddevelopmentin1971,recalled,“TheB-70wascapableonlyofoperatingveryhigh,veryfast,andwhentheSAMmissilescameintooperationaluse,theB-70found it could not operate in its designregimen,andithadlittleresidualcapabil-itytooperateinotherregimes.”40

For aircraft without the SR’sone-of-a-kind performance, survivabil-ity would increasingly rely on means ofdeceiving and thwarting the enemy’sability to detect, track, and engage air-craft.WorldWar II-eraattemptstomountelectroniccountermeasures to radarde-tection had paid off. When Allied ECMjammed German AAA fire control andground-controlled intercept (GCI) radar,visualtargetingofthe88mmairdefenseguns proved much less effective againstbombers flying at 25,000 to 29,000 feet.The addition of ECM was estimated tohave reducedtheAlliedattrition ratebyasmuchas25percent.”41Nowthatradar

controlledeachstageoftheduel,evadingordeceivingfirecontrolradarsandmissileseekersbecameanessentialpartofthesurvivabilityduel.

Operational Challenges: SAMs in Vietnam Five years after the U-2 incident, a North VietnameseSA-2shotdownanAmericanF-4ConJuly24,1965.Theprob-lems of survivability were multiplied for the military aircraftthatoperatedinVietnam.AircraftliketheF-4,F-105,andtheF-111 were designed with features like speed, range, andbomb-carrying capacity in mind. Like their old World WarII-era cousins, the aerodynamic features of these aircraftmadethemlargeradarreflectors.Theircrewsmighttake itforgrantedthatenemyradarwoulddetectthematsomepoint.However,thespeed,maneuverability,andtacticsthatpilots reliedon for survivabilitycouldnotcompletely shieldthemand theirwarplanes from the threatof radar-guidedmissilesclosingatMach2orfaster. By the time the Rolling Thunder operations of 1965-68were in full swing, survivability consisted of multiple duelsbetweenattackingaircraftandthefighters,SAMs,andan-tiaircraft defenses they might encounter. Early warning ra-darcuedfighterinterceptors.SAMbatteriesusedtheirownacquisitionradarstodirectthefirecontrolradar.Antiaircraftgunswithradardirectionfindingoperatedautonomouslytoacquireandshootataircraft. Thedeploymentofradar-guidedSAMbatteriescreatedanewduelbetweenattackersanddefenders.Radarguid-anceforcedthedevelopmentofnewandaggressivetac-tics for survival in theendgame. Forexample, thefirst SA-2missilesreactedslowlyonceinflight.Aircrewsrapidlydevel-opedtactics toevadethemissilebycarryingoutextrememaneuvers that would cause the missile to overshoot andmisstheaircraft.Thechartonp.25diagramsonetacticde-


26

velopedtopitthemaneuverabilityoftheaircraft and the skill of the pilot againstthe missile’s radar guidance and perfor-manceparameters. TheriskofSAMengagementaffectedairoperationsbynarrowingtheoptionsfortactical employment. If aircraft flew in atmedium or high altitude, they would bedetected, tracked, and potentially fireduponby SAMs. If they flew in low, theair-craftwouldgainprotectionfromthenapof the Earth and be able to stay belowtheSAM’sminimumengagementaltitude.Low-altitude attacks, however, plungedaircraft intoaregionofdenseantiaircraftgunfire.Thechartattoprightshowshowmulti-layered defenses increased surviv-abilitythreatsatallnormaloperatingalti-tudes. Here, the survivability duel increasedinintensity,asabarrageofthreatsposedsignificant risks to aircraft at all altitudes.Asoneauthorputit,by1968,the“enemy’suse of the electromagnetic spectrum totrackandshootdownfriendlyaircraftwasa serious problem, and the requirementto neutralize it spurred vigorous activityinboththetraditionaltechnicalECareasand the pragmatic world of fighter tac-tics.”42

Attheheartoftheproblemofcoun-tering SAMs was the system used to de-tect,track,andfireataircraft.Radarassist-edinallphases.InWorldWarII,chaffandcountermeasuresprimarilysoughttoblindthe defenders’ long-range detection fora period of time. By the late 1960s, ECMhadtocounteranddefeatweaponsen-gagementaswellastoshroudattackersfromearlywarningandtracking.Thechartaboveillustrateshowtenuousearlywarn-inglinkstooperationscentersattemptedtohandletargetacquisitionandpassinformationontofirecontrolradarstolaunchSAMs. More integratedairdefensesstrungeachstageofthedueltogether.Successfuldetectionandtrackingledtoen-gagementandenhancedprobabilityofkill.Radarlinkedthestagesof the survivabilityduel together intoan integratedairdefensesystemthathadthepotentialtobemuchmoreeffectiveandlethal. Electronic countermeasures brought back an elementof tactical surpriseandgaveaircrewsabetter survivabilityadvantage by making it more difficult to complete each

stage of radar tracking and engage the aircraft. Electron-iccountermeasuresthrewinabandofclutterthatcuttheeffective range of acquisition and fire control radars. ECMoptimizedfordifferentwavelengthfrequenciesandengage-mentscouldjamawarheadseekerorjamtheradardirect-ingit.Thetacticaleffectwastoreducethetimefortheen-emymissilebatteriestoengage,asdepictedinthetopchartonp.27. Stand-off jamming was not unlike what the British andAmericansaccomplishedinWorldWar II. Itmaskedaircraftfromearlywarningradarstowithinacertaindistanceofthetarget.Morepowerfulsystemsindedicatedaircraftsuchas

27


theEB-66raisedthenoiselevelandcouldreducetheeffec-tivetrackingrangeofearlywarningandfirecontrolradar.Bycreatingabeltofjamming,ECMlimitedthetimetheaircraftwasvulnerabletodetectionandtracking,therebyshorten-ingtheenemy’sresponsetime. Successful jamming depended on achieving an ad-equate“jamming-to-signal” ratio.TheJ/S is themeasureofthestrengthofthenormalradarreturnfromanaircraftandthesignalwhichthehostileradarreceivesfromthejammingaircraft.Itvarieswiththesquareofthedistancefromthejam-mer to the receiver being jammed, and thus at great dis-tances,jammingsystemsarelesseffective. Because of its size, the EB-66 could carry larger, morepowerful radar jammers to extend protection to many air-craft.Still,gettingthemosteffectiveresultsfromjammingre-quiredacombinationoftechniques.Inaddition,anaircraftcouldproduceonlya limitedamountofpowerto jamen-emyradarreceivers. New methods of suppressing air defenses focused ondestroyingradarsandSAMbatteriesoutright.Lethalsuppres-sionofenemyairdefenses (SEAD)developedasawaytobreaktheeffectivenessofindividualbatteriesandoftheen-emyairdefensesystemasawhole.WildWeaseltactics,forexample,combinedanextremelysophisticatedradar-seek-ingsensorwithanti-radiationmissilesthathomedinonradaremissions. The various electronic countermeasures (non-lethalSEAD)andlethalSEADtacticsforsuppressingenemyairde-fenses ledplanners toscheduleaveritablearmadaofair-crafttoescortthebomb-droppers.Strikepackagesliketheonedepicted inthechartbelowsoughttocounterall thepotential engagements that the air defense system couldmountagainstalargenumberofaircraftbeingtrackedbyradar.FightersdefendedagainstMiGs.Chaffand jammingmaskedthepackage’sapproachandshielded it toade-greefromSAMs.TheIronHandcomponentssoughtoutnestsofmissile sitesand radar-directedantiaircraftgunsandat-temptedtodestroythem. By combining both lethal and non-lethal SEAD, andfighterescort,thetypicalVietnamstrikepackagelayeredmultiple techniques for survivingdetection, tracking,andattacksbyenemySAMs,AAA,andfighters. AnoperationattheendoftheVietnamWarillustratedhowtheelementsofthestrikepackagesworkedtogethertoenhancesurvivabilityforbombers.“ThestrikepackagewasperhapsthesignificantkeytothesuccessofOpera-tionLinebacker,”concludedanofficialUSAFhistory.43

Linebacker II, the lastmajorairoperationoftheViet-namconflict,wasan11-daybombingcampaignagainsthigh-valuetargetsinNorthVietnam.Itpointedouthowahost of electronic countermeasures now assisted in theduel.SomeplanningestimatesforLinebackerIIexpectedattritionratesashighasfivepercentbecauseofheavyde-

fensesaroundtheselectedtargets.44Toprotecttheforma-tions,atypicalstrikepackageforLinebacker IIstartedwithhigh-speed,low-levelattacksbyF-111susingterrain-followingradarwithagoal to takeoutSAMsitesandcraterenemyairfields. F-4sthenblanketedtheareawithchaffsothatradarop-eratorscouldnotdistinguishtheB-52sfromthefalsesignalsontheir scopes.F-105WildWeaselsalsoaccompaniedthestrikepackageandusedantiradarhomingmissilestohitSAMsites. ForthefirstLinebackerIImissions,67B-52slineduponeafter the other in a 70-mile-long formation known as the“babyelephantwalk.”TheB-52sattackedabout20minutestoanhouraftertheinitialassaultandwouldcomeinwaves,consistingof21to51bombersand31to41supportaircraft,separatedbyafewhourseach.45ThebombersfacedSAMsfiredinshotgunpatterns,inwhichtheNorthVietnamesesentupsix-missilesalvosatatime.Onegunnerspotted32SAMsfiredatornearhisplane.46

The B-52s were in the most danger when they had tooverflythetargetareatoreleaseweapons.Atthatmoment,astheplanereleaseditspayloadandmadea100-degreeturn to depart from the target area, the B-52 exposed its


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maximum radar profile to the enemy. Linebacker II’s statis-tics confirmed the dangers inherent in these employmenttactics.Twelveaircraftwerelostinthefirstthreedaysoftheoperation,includingnineB-52s,partlyduetothispredictablemovethatexposedthetailsectionoftheaircrafttoradar.47Tacticschangedon latermissionsbutproblemscontinuedtohampertheformations.TheB-52’sgiantRCScouldnotbeconcealedbyjammingas itnearedthetarget.Sometimeschaffcorridorsweredispersedtooquicklybecausewinddi-rectionsdifferedfromforecasts;someoftheB-52swereolderDmodelsanddidnothaveupgradedECMequipment. Inshort,thepotentialvulnerabilityoftheB-52swashigh. TheAir Forceultimatelyadaptedby layingwidechaffblankets instead of corridors, varying flight patterns andbombing runs, and installing modified radar jammers tomeet new enemy threats. However, in the end, 27 aircraftwerelostinthe11-dayoperation,including15B-52sover729sorties,alllosttoSAMs.TheB-52attritionrateoftwopercentwouldhaveproveddifficulttosustainoverseveralweeksormonths,exceptforonefact.BytheendofDecemberabout900SAMshadbeenexpended,andHanoi’sSAMinventorywasnearlydepleted. LinebackerIItypifiedtheshort,intensiveairoperationsthatdottedthenextdecade.WhileLinebackerIIwascountedasa success for its role in restarting the peace negotiations, ithadalsodeliveredevidenceoftheincreasingvulnerabilityofbombersand strikeaircraftattackingheavilydefended tar-gets.AsSoviet-madeairdefensesspreadtomanyotherna-tions,survivabilityandtheabilitytocompletemissionsincreas-inglydependedonhowaircraftfaredagainst integratedairdefenseswithSAMsasthecenterpiece.In1973,forexample.Israellost40aircraftinasingledayintheGolanHeights.The10percentattritionrateforcedIsraeltohaltairoperationsevenasArabforcesthreatenedtooverrunIsraeligroundpositions.48TheIsraelisrefocusedtheireffortstowardgainingairsuperiorityandthenhelpeddestroytheinvadingforces. Stand-off jammingbecameso important toairopera-tionsthatdedicatedplatformsliketheEF-111andtheEA-6B

were modified to perform the mission. In the 1980s, for in-stance, the EF-111 with theALQ-99 could jam radar in theVHFtoJ-bandsoveradistanceofabout124miles.Thus,fiveEF-111scouldprovidestandoff jammingcoverageforare-gionrangingfromtheBalticSeatotheAdriaticSea.

The Libya Raid, 1986 InMarch1986,USNavywarshipsininternationalwaterscrossedLibya’sarbitrary“lineofdeath,”drawnnearthe32ndparallel.ALibyanSA-5SAMbatteryatSirtefiredattwoF/A-I8HornetsfromtheUSSCoral Seaflyingcombatairpatrol(CAP)overthebattlegroup.Firedatextremerange,themissilesdidnothittheirtargets.ButtheSA-5firingsunderscoredtheprob-lemsoflaunchingastrikeagainstanintegratedairdefensesystem. The next month, April 1986, the US conducted a raidagainsttargetsinLibyatopre-emptfar-reachingterroristat-tacksthatUSintelligenceindicatedwerebeingplannedbytheLibyans.Stand-offjammingwaskeytotheexecutionoftheoperation.Libya’sairdefensesystem,suppliedbytheSo-viets,wasbuilt tocounterknownUSstrengthstothegreat-estextentpossible.TheLibyans reliedondense, redundantcoveragebyradarsoperatingonmultiplefrequenciesandwith different waveforms.All these features were designedtocomplicate the tasksof jammingandantiradiationmis-silesliketheShrikeandtheHigh-SpeedAnti-RadiationMissile(HARM).Hardenedlandlinessoughttoprotectagainstanat-tempttoshutdownthesystem.49

The primary tactic of the Operation Eldorado Canyonraid was a high-speed, low-altitude night attack. As onestudynoted,“atattackspeeds,givennoadvancewarning,anenemy radarwouldhave less than threeminutes to lo-cate, identify,track,andallocateaweaponbeforetheat-tackerwouldbeoverthesite.” Jammers could cut the time even more by screeningtheattackersfromdetectionforalongerperiod.Indeed,theEF-111andEA-6BjammerswereattheirbestinjammingtheolderLibyansystems.

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Still, SA-2, SA-3, SA-6, and SA-8 mis-siles came up against the strike pack-age. Aircraft “encountered heavysurface-to-air missile activity near Trip-oli and at one downtown target nearBenghazi.”50Thedenseairdefenseenvi-ronmentwasonatrajectorytogreatlycomplicatesustainedairoperations.

Evolving Air Defenses and the Limits of ECM TheproliferationofadvancedSAMsand, increasingly, of integrated air de-fense systems, made the challenge ofsurvivabilityallthegreater.Forexample,in Vietnam, early warning radar inter-ceptswerepassedtobothfiltercentersandcommandandcontrolcenterstomanagefighterinterceptoperations.ThedreadedSAMbat-teries, however, generally did not receive consistent earlywarning. In contrast, the air defenses around Libya in the1980sgathereddetectioninformationatasinglepointandusedtheadvancedwarningtoallocateairdefenseweap-ons. Still, the Libyan system was not the most modern andelectronic countermeasures had been developed to useagainst it. ItwasthemoremodernandcentralizedIraqiairdefensesystemthatwouldpresentaqualitativelydifferentchallengesomefiveyearslater. Overshadowing all the Third World systems was, ofcourse,theintegratedsystemoftheUSSR.Rapidadvancesincomputingtechnologyincreasedtheflowofinformationthroughtheairdefensesystem.Centraldirectionandinte-grationofairdefensesimprovedtheirefficiencyandlethal-ity.TheemergenceofadvancedSAMsliketheSA-10wouldposeincreasedsurvivabilitychallenges. Aslongasattackaircraftremainedstrongradarreflec-tors,itwouldtakeagreatdealofjammingtoconcealtheirsignatures.ECMhadinherentlimits.Weightrestrictionsmeant

that thepowerof theairborne jammerwouldneverbeasgreatasthepotentialpoweroftheground-basedradarat-temptingtotrackaircraft.Moreover,changesinfrequenciescould invalidate the countermeasures process. As then Lt.Gen.JosephRalston,deputychiefofstaffforplansandop-erationsontheAirStaff,reflectedin1994:

“After Vietnam and during the 1970s, it seemed we were engaged in a never‑ending struggle to provide our aircraft with modern radar‑warning receivers and jammers to coun‑ter each new threat. Frequencies changed, new SAMs were fielded, wartime modes surfaced ... it seemed we were in an infinite ‘go to’ loop of ECM and ECCM.”51

AccordingtoRalston,muchofthe“allureofstealthwasinitsabilitytogetusawayfromelectronicwarfare.”Surviv-ability again placed a limit on the effectiveness and effi-ciencyofairoperations.Thus, thenextphase in theradargamewouldbe tomaster the scienceof reducing radarreturns.

WINNING THE RADAR GAME Minimizing aircraft radar return was an idea that oc-curredtoBritishengineersduringWorldWarII.InAugust1941,Britishresearcherssubmittedaroundofproposalsformodifi-cationstoaircrafttorenderthem“undetectablebynormalRDF” or radar. Their plan was to adjust the aircraft’s radia-tiontomatchthebackgroundlevelofradiationfromtheairaroundit.Increasingtheresistivityoftheaircraft’sskinmightshort-circuittheradiowave;andinsteadofreflectingback,the wave could be shunted into a gap where the wave-

lengthwouldbeimpeded.Ifmaterialwiththerightintrinsicimpedancewasfound,amodifiedmatchingsystemcouldpreventreflection,butonlyatcertainfrequencies. Althoughtheynevertooktheideabeyondafewtheo-retical papers, these British engineers had hit upon a con-cept that would become much more compelling by the1960s. Ifanaircraftcouldperhapsbeshapedtomakethereturnsignallesspowerful,theneteffectwouldbetomaketheaircraftappearontheradaroperator’sscopelaterthan


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expected,orperhapsnotatall,therebygivingtheaircraftanaddedmeasureofsurprise. Across the Channel, an unusual German aircraft de-signhadalsograspedat radar-defeating features. In1943,theshortageofmetalledWalterandReimerHortentode-sign an aircraft with improved performance, plus shapingandcoatingsthatmighthavereduceditsradarreturn.TheHortentwin-engineflyingwingbomber/reconnaissanceair-craftusedplywoodandcharcoalmaterials thatefficientlyabsorbed the long centimetricwavelengths of the period.TheHortens’initialinterestintheflyingwingdesignstemmedfromtheirdesiretoeliminatesourcesofparasiticdrag.Therewerenoverticalsurfacesontheplane,andthecockpitandBMW003turbojetpowerplantswerehousedentirelywithinthewingitself.52Thecentersectionofthewinghousedtheenginesandcockpitandwasmadeofconventionalweldedsteel-tubeconstruction.The restof theplanewascoveredwithplywoodsandwichedaroundacenterofcharcoalex-ceptfortheengineexhausts,whichwerecoatedwithmet-al.53

Inearlyflighttests,theHorten,alsodesignatedtheGo229,attainedalevelspeedof497mphbuttheprototypecrashedduringlandingandwasdestroyed.AircraftmakerGothastillhadproductionprototypesinworkwhenUStroopscapturedtheFriedrichsrodaplantinlateApril1945.Atthattime,oneGo229prototypewasbeingpreparedforflighttesting,andsever-alotherswereinvariousstagesofproduction.Hadtheaircraftgoneintoservice,itsestimatedmaximumspeedwouldhavebeenaformidable607mphanditsmaximumceilingabout52,500feet,witharangeof1,181miles.54

Reducingradarreturnwasnotforgottenafterthewar.InMarch1953,whentheAirForcedrewupspecificationsforanewreconnaissanceaircraft,Paragraph2(g)ofthespecifi-cationsstipulatedthat“considerationwillbegiveninthede-signofthevehicletominimizingthedetectabilitytoenemyradar.”55Withinadecade,designerswouldtakethefirststepstowardalowobservableaircraft.

Steps Toward Low Observables By the 1960s, speed and high-altitude performancewerenotenoughtoevadethenewestgenerationofguidedmissiles. Low observable (LO) technology grew out of theneedtominimizetheamountofradarreflectedbackfromtheaircraft. Intheory, itwaswidelyunderstoodthatspecialcoatings,materials,andshapescouldmakeobjectslesseasytodetect. Both theU-2andespecially, theSR-71,exploredtheseconceptsevenwhileputtingtheprimaryemphasisonaltitudeandspeedforsurvivability. The SR-71 was the first aircraft to incorporate low ob-servablesasadesignfeature.LockheedengineerskeptthetailsoftheSR-71assmallaspossibleandconstructedthemwith as much radar-absorbing material (RAM) as possible.Designersoftheaircraftalsomodifiedtheroundedfuselage

byaddingachine—alateralslopedsurfacethatgavethefuselagetheappearanceofacobra—thatleftthebellyoftheaircraftessentiallyflat.This reduced radarcross sectionbyasmuchas90percent. Inaddition,LockheedmadeextensiveuseofRAMinallthesharphorizontaledgesoftheaircraftthatmightbehitbyradarwaves, includingchines,wing leadingedges,andelevons.TheRAMconsistedofaplastichoneycombmate-rialthatmadeup20percentoftheaircraft’sstructuralwingarea. Although the SR-71 was 108 feet long and weighed140,000pounds, ithadtheRCSofaPiperCub. In fact, theSR-71 had lower radar cross section than the B-1 bomberbuilttwodecadeslater.56

As tantalizing as their promise appeared, low observ-ables depended on capturing so many variables in theaircraft’s signature that it took a revolution in computingtechnologies to make the engineering tasks feasible. Bal-ancedsignature reductionultimatelycameto includenotonlyradarreturn,butinfrared,visual,acoustic,andlasercrosssectionreduction,andreducingemissions fromtheaircraftradar. However, the first challenge was to understand andquantifythebehaviorofradarwavesastheyencounteredthemanydifferentshapesandsurfacesonanaircraft.

Calculating Radar Return Morethan30yearspassedbetweentheBritishhypoth-eses about blending aircraft into background radiation,and the events that made shaping an aircraft to lower itsobservabilitytoradarareality.AmajorbreakthroughcamewhenLockheedSkunkWorksengineerDenysOverholsersawsomethingintheworkofaRussianradarscientist.TheRussian,PyotrUfimtsev,hadrediscoveredthattheequationsofScot-tishphysicistJamesClerkMaxwellcouldbeusedtopredicthowacertaingeometricshapewouldreflectelectromag-neticwaves.Inapaperfirstpublishedinthemid-1960s,Ufimt-sevappliedthisprincipletocalculatingthesumoftheradarcrosssectionsofdifferentgeometricshapes. Calculationsofradarreturndependonlawsgoverningthepropertiesofelectromagneticradiation.Electromagnet-icwavesbehavethesamewhether theirwavelengthputsthem in the radar or optical light regions. Maxwell’s equa-tions,formulatedinthelate19thcentury,establishedbound-ary conditions for the behavior of electromagnetic waves.UfimtsevpostulatedthatMaxwell’sequationswouldmakeitpossibletocalculatethebehaviorofradarwavesretransmit-tedfromareflectiveobject.Theradarreturnwoulddependinpartontheshapeoftheobject.Bytreatinganaircraftasagroupofgeometricshapes,eachwithitsownradar-reflect-ingproperties, itwouldbepossibletocalculatetheRCSoftheaircraftasawhole.Then,intheory,anairvehiclecouldbedesignedwithgeometrythatminimizedtheradarreturn. Building on the direction suggested by Ufimtsev, RCSengineeringusedprinciplesfromphysicalopticstoestimate

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the type of scattered field that would be createdwhenradarwavesencounteredanaircraft.TheradarrangeequationandtheequationforcalculatingRCSarebothbasedonphysicalopticsmethods. The sum of the major reflective components oftheaircraft’s shape isdefinedas radarcross section.RCS is the area (width and length) of the scatteredwavefieldbeingreturnedtowardtheradar.Generally,the sizeof the radarcross sectionofaconventionalaircraftismuchlargerthanthephysicalsizeoftheair-craft.TheRCSofanaircraftdeterminestheamountofthe sending radar’s power that is reflected back forthesendertoreceive.AnRCSistypicallymeasuredinsquaremetersor indecibelspersquaremeter,oftenabbreviatedasdBSM. Radarwavesreflectandscatterinmanydifferentways. Each featureofanaircraft,carefullydesignedforitspower,strength,andaerodynamicqualities,canhavequiteadifferentmeaningwhenconsideredfromthestandpointofradarcrosssection,asshowninthemiddlechart. Todesignlowobservableaircraft,engineershadtoreliablypredictandcontrolthemultipleformsofra-darreturnthatadduptotheRCS. Principlesofphysicalopticsdefine severaldiffer-ent types of radar wave reflection and scatter thatformtheaircraft’sradarreturn.Forexample,specularreflectionoccurswhenwavesarereflectedbackataknownangle.Diffractiontakesplacewhenwavesen-counteranedge—likeawingtip—andarediffractedin all directions around a cone.Traveling waves canbecreatedthatarenotreflectedordiffractedimme-diately,buttravelonalong,thinbodynose-ontotheincomingwave.Similarly,creepingwavesareliketrav-elingwavesthatpropagatearoundtheshadowareaorbackofthetarget.Wavesgeneratedintheobjectbytheemittedradarwavesarekeptincheckbytheobject’selectromagneticcurrents.Whenwaveshitacrack,slope,ordifferentmaterial,theyscatter. Wavesdonotsimplybounceoffandreturnfromsurfaces.Wavesmaybouncearound incavitiesandductsandgenerateadditional return. Similarly, radarwavescanscatterinsideacavitysuchasacockpitorengineinlet. The principal contributors to radar cross sectioneachdemanddistinctanalysisoftheirbehavior.Exam-iningeachofthesemechanismsinturndemonstratesthemanydifferentvariablesthatdesignersmustcon-troltoachieveareducedRCS.

Specular Reflection Specularreflectionisthemajorsourceofradarre-turn,andminimizingspecularreflectionisthefirsttask


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of LO design.A large, flat plate reflects radar return like amirror.Conventionalaircraftwithlargeverticalstabilizersaretextbookexamples. Initsphysicalproperties,specularreflectionislikeamir-ror.Thedirectionofthereflectedwavesdependsonphysicallawsthatrelatetheanglethewavestrikesthetargettotheangleatwhichthewaveisreflected.Theselawsalsoallowdifferentaircraftshapestoproducedifferentradarreturns. Inspecularreflection,theangleatwhichawavestrikesanobjectalsodeterminestheangleofthereflection. Whenwavesstrikeanobjectatrightangles,moreofthereflectedwavesreturninthedirectionofthesender.Varythe“incidence angle,” or angle at which the waves strike theobject,and—tosatisfyopticallaws—moreofthewavesaredirectedoutsidetheplanetransversetotheviewer. The mirror-like return caused by specular reflectionmakesitthelargestsinglecontributortoRCS.Inthesimplestterms, theangleof theobjectcandetermine reflection.Avertical plate will have maximum reflection when perpen-diculartothedirectionoftheincomingwave.Aplateslant-ed so far back that it is almost flat will direct more of thescatteredfieldawayfromthesender’splaneofview.Geo-metricshapeaffectsspecularreflection.AdiamondshapewillreflectwavesinanX-shapedsignaturethatanglesreturnawayfromtheprincipalplaneoftheviewer.AsquareplatewillhaveadifferentpatternresultinginalargerRCS. Specularreflectioncanbecalculatedbecauseitmustsatisfy physical laws. An observer walking past a car on asunnydaywillseethemaximumglintorspecularreflectionfromthecar’swindshieldataspecificpoint. Thispointcorrespondstothemomenttheobserver in-tersects the reflected angle, as determined by the angleof the sunbeams. The angle at which sunbeams strike theobjectmustcorrelatetotheangleatwhichthebeamsarcreflectedbytheobject.

Whenanobjectisperpendiculartotheradar,theangleof thereflectionwillbemore likely to fallwithintheradar’splaneofview.Whentheobjectistiltedaway,theincidenceanglefromthesamesourceismoreacute.Tosatisfytheopti-callaws,agreateramountoftheradiationisscatteredatanangleawayfromtheplaneofthesender’sradar. ThetypesofshapesthatcontributemosttoRCSaredi-hedrals,alsocalledretroreflectors—planesurfacesat90de-greestooneanother.Theyappearonmanymodernaircraftfor sound aerodynamic reasons. For instance, viewed fromtheside,theF-15Eaglehasasurfaceareaofabout25squaremeters.Yetbecauseoftheaircraft’snumerousdihedralsandsurfacespointingflattotheradar,aside-aspectRCSfortheaircraftismanytimeslarger,aboutthesizeofahouse.Onesolution to the sideaspectproblem is toeliminateverticalstabilizers,aswasdonewiththeB-2stealthbomber.

Diffraction When specular reflection is reduced, other scatteringmechanisms frommanyfeaturesofanaircraftcangreatlyaffecttheradarcrosssection.Diffractionoccurswhenwavesstrikeapointsuchasawedgeortip.ThesourceofdiffractioncanbeassmallastheheadofascrewthatisnotflushwiththesurfaceandisnotcoveredwithRAMmaterial.Diffractionscatters waves in all directions, obeying physical laws thatshape the diffraction like a cone. Signature reduction re-quiresensuringthatthescatteredelectricfieldiscontrolledanddirectedawayfromthesendingradar. DiffractionfromaerodynamicfeaturesonconventionalaircraftcanbealargesourceofRCS.Conicalpoints,sharpcorners, and even rounded tubular surfaces each causetheirownuniquediffractionpatterns. A special case of multiple diffraction occurs inside acavity.Wavesinsideacavitylikeacockpitoranengineinletscatterincomplexways.

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Thiscavitydiffraction is the sameeffect thatcausesacat’seyetoglow.Asmallshaftoflightenterstheroundedcavity of the eyeball and bounces around inside it, pro-ducingabrightflashorglow.TheintensityofthescatteringincavitiesandductscansignificantlyincreasetheRCSofanobject,especiallywhenspecularreflectionanddiffrac-tionhavealreadybeencontrolled.

Traveling Waves Travelingwavespresentauniquecasebecausethetar-getobjectbecomesanantennaandatransmissionline.Whengrazinganglesareslight,thetargetcollectsenergyand transmits it along the surface. A discontinuity like acrack,slopeorroughspotofmaterialwithadifferentcon-ductivitycancausediffractionofthetravelingwave. Verythickmaterialswouldberequiredtodissipatethetravelingwave’senergy,sotheprimarytechniqueistode-flectit.Forexample,sweptedgesonatrailingwingedgecan direct the transmitted energy away from the direc-tionofthethreat.Also,ondoublycurvedbodies,addingathinwiretotheendoftheobjectcanattractthetravelingwaveandretransmititlikeanantenna. Traveling waves create challenges on the shop floorand in future maintenance, too.As one Lockheed F-117engineerputit,“Wecouldn’talloweventhetiniestimper-fectioninthefitofthelandinggeardoor,forexample,thatcould triple the airplane’s RCS if it wasn’t precisely flushwiththebody.”Anyprotrusions,suchassmallfairings,grills,domes,andwingtips,canprojectradarwavesbacktothesender.Evenrivetsandfastenerscanactasradarreflec-tors.

Radar‑Absorbing Material Oncetheaircraft’sbasicshapehasbeendesignedforlowerRCS,asecondstepistoapplymaterialstothesur-facearea that further reduceRCS.One important tech-nique,serratededges,isactuallyageometricabsorber.Aknifeedgetendstoscattermorewavesbacktowardthereceiver.Serratededgesusethegeometryoftherowsofpyramidstodiffractwavesawayfromthesendingradar. Radar-absorbingmaterialsareusedtoattenuateradarwaves. InWorldWar II,RAMcoveredGermansubmarinesnorkels,whichwerebecomingeasypreyforAlliedaircraftequippedwithcentimeter-waveradar.Sumpf,asandwichofrubberwithcarbongranulesembeddedinit,wassup-posedtoabsorbradarpulses,reducingthestrengthoftheechoandmakingthemlessdetectabletoradar.Inlabora-torytests,Sumpfwaseffective,thoughitwaslessusefulinseatrials,asthesaltwatertendedtoremovethecoveringanddiminishitselectricalproperties. AnearlyexperimentinRAMforaircraftwastheU-2’sfer-rite-lacedpaint.Thepresenceofironinthepaintchangedthemagnetizationoftheradarwavesinordertodiminish


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return.However,sinceironisagoodconductor,thelossofenergywasnotsmallenough.Othermaterialsreducedra-darreturnthroughpassivecancellationorimpedance.TheBritishproposalsof1941speculatedonthepossibilityofim-pedance.Useofmaterialswithdifferentelectricconduct-ingpropertieswouldintroduceasecondscatteringmecha-nismthatcancelsoutthefirst.

RCS Reduction Features for Aircraft Makingagoodstealthairplane isa littlebit likemak-ingabadtransmittingantenna.Thesenderwouldreceivesomuchlessradiatedpowerthattheaircraft’sreturnsignalwouldfallbelowtheradar’sdetectionthresholduntiltheair-craftwasverycloseto the radar.However, lowering radarcrosssectionrequiresatrade-offbetweenideallowobserv-ablefeaturesandaerodynamicperformanceneededforacombataircraft. Aircraft like theA-10weredesigned forperformance,not stealth. For a conventional aircraft, the largest returnscomefromsideaspects,becauseofitsverticalstabilizer,fu-selage,andfromspikesonthenose,fromengineinlets. Lowobservabilitytoradarwasnotamajordesignfea-ture for the premier US fighter and attack aircraft that en-tered service in the1970sand1980s: theF-14, F-15, F-16,andF/A-18.However,inafewcases,certainfeaturesbuiltinforaerodynamicperformancehelpedreduceRCS.OutsidetheUS,forexample,theSovietSu-24hadanengineductde-signthatreducedthepropagationofradarwaves.Aconicalnosesectionaidssupersonicflightonadvancedfighters,anditalsominimizesnose-onRCS. The goal of low observables is to reduce RCS. Signifi-cantreductionsinRCSputtheF-117,B-2,andF-22intothestealthzone.Thestandardscale(p.35)fromatextbookonradarcrosssectionengineeringshowsthecontrast. Whenstealthaircraftachievedlowersignatures,whatthatmeant,inpractice,wasthatlowerRCSdecreasedtheeffectivedetectionandtrackingareaoftheradar. Currentcombataircraftfallatmanydifferentpointsonthestealthspectrum.Forexample,modificationstoconven-tionalaircraftcanhelpminimizeradarreturn,especially inthefront-aspect. On theF/A-18E/F, forexample,anumberof signaturereduction techniquesare scheduled tobeapplied.Agrillcoverstheairintakes.ApplyingRAMtoleadingedgescanalsoreducereturn.ModificationstendtoreduceRCSmostfrom the head-on aspect where aircraft are most vulner-able. AtruestealthaircraftisonewhereRCSreductionwasamajordesignobjectivefromthestart.Stealthaircraftbeginwithshapesthatbothminimizeandcontrolreflectionanddiffraction,therebyreducingRCS.TheF-117wasthefirstair-craftwithlowobservablesasthemajordesigncriteria.Flat,angledplatescontrolledspecular reflectionand reduced

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diffraction.Theaircraft’scollageofparallels reflectsageo-metricdesignintendedspecificallytocontrolradarreturn. Swept wings redirected radar energy away from thefrontalsectoroftheaircraft.RAMappliedtotighttolerancesminimized diffraction from traveling waves while applyinggeometric scatteringand impedingwave return.A screencoveredtheengineductsandthecanopywasshielded. Diffusersandbafflingprevented radarwavesenteringtheengine intakefromhittingtheengine itselfandreflect-ingback to the receiver.Diffuserscovered the frontof theintakeandscreenedoutradarwavesbyusingawiremeshthatwassmallerthanthewavelengthoftheradar,similartothescreenonamicrowaveoven’sglassthatpreventmicro-wavesfromleavingtheinterioroftheappliance.TheintakeontheF-117wascoveredwithafinegrillmeshwhosegapsweresmallerthanthewavelengthsofenemyradar.Anyra-darenergynottrappedbythismeshwasabsorbedbyRAMliningtheductleadingtotheengine. Insum,theF-117’sprincipalpointsofradarreturnwerecontrolledtobewellawayfromahead-onaspect.Asthechartat rightbelowshows,shapingdiminishesradarreturn

anddirectsitawayfromtheradar,re-sulting inadramaticoverall signaturereductionforthegivenarea. Facetingliterallyfocusesoraimsthestrongestpointsofreturnawayfromthedirectionof the radar.Othermeasuresconstraindiffractionthatmightenlargetheaircraft’ssignature. In the 1980s, the design of the B-2followed similar principles, but tookthemastepfurthertoincludesmooth,roundedsurfaces.ThelargesizeoftheB-2,designedforlongrangeandhighpayload, created new design chal-lenges. Accordingly, the B-2 met the

challengewithadvancedshapingtechniquesandcurvedsurfaces thatenabled it toachievedramatic signature re-ductiondespiteitsphysicalsize. The B-2 went into production with 10 distinct trailingedgesatconstantanglestoensurethatradarenergywasreflectedfromthetrailingedgesofthewingintotwodirec-tionswellawayfromtheimmediaterearoftheaircraft.Theflying wing design eliminated vertical control surfaces andmadeiteasierbothtoincorporateRAMandtohideenginesand ordnance within the fuselage because the entire air-craftbodyproducesliftandcauseslittledrag. The F-117 and the B-2 both traded some features ofaerodynamicperformanceinordertoachievestealth.Intheearly 1980s, theAir Force developed a requirement for anadvancedtacticalfighterthatwouldachievestrongaero-dynamicperformanceandmaintainaverylowobservableRCS.Theadvancedtacticalfighterwouldcombineair-to-aircombatcapabilitieswithanair-to-groundrole.Afteracom-petitivefly-off in1991, theAirForceselectedtheLockheedYF-22prototypeovertheNorthropYF-23.


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TheF-22wasdesignedasbothastealthaircraftandafast, highly maneuverable fighter. Its rudders are set at anangletolimitreturn.Thinsweptwingspointthesurfacenor-malsofradarreturnawayfromthehead-onaspect.Fromallaspects, the F-22’s design follows the principles of control-lingandminimizingradarreturnthroughshaping.Thetrailingedges of the wing and elevator are parallel, as are manyotherseriesoflinesaroundtheaircraft’sbodyandwings.Airinletsanddumpshaveserratededgesandmetalmeshcov-erstolimitelectromagneticwaves.Atthesametime,theF-22hasmorewingareathantheF-15,makingitcapableofhighG-forcemaneuvers. Anotheraircraft,theJointStrikeFighter(JSF),isstillinde-velopment. Plans call for the tri-service aircraft to achievesignature reduction and to perform multiple roles. The AirForce,Navy,andMarineCorpseachplantoprocuremodelsof theJSF thatare signature-reducedand tailored to theirspecificmissionrequirements. Reduced RCS is the central factor in survivability be-causeofthelongrangeofradardetection.However,surviv-abilityalsodependsonreducingreturninotherareasoftheelectromagneticspectrum,asthenextsectionwilldiscuss.

Other Components of Stealth Diminishingradarcrosssectionisthemajorcomponentof lowobservability,but it isnottheonlytask.LoweringtheRCScanmakeothersignaturesstandoutmoredramatical-ly.Visual,acoustic,and infrared signaturesmayhavebeenovershadowed in an older aircraft with a very large RCS.However,astealthaircraftdesignmustalsoworktocontrolthesignatureacrosstheelectromagneticspectrum. Noisecanconveysignificant informationaboutanair-craft.Noisecontributestodetection,althoughtherangevar-iessubstantiallywithfrequency.Distinctivenoiseslikehelicop-terrotorbladescanhelpclassifythetypeofaircraft.Steady

tonesmayprovideinformationtodetermineaDopplershift.Minimizingmajor sourcesof sound,especially fromenginesandairframes,isanimportantcorollarytostealth. Stealth aircraft also incorporate reductions to infrared(IR)signature.Allobjects radiateapatternofheat,exceptthoseatabsolutezero.AlthoughengineheatandexhaustarethemostsignificantsourceofIR,frictionbetweentheair-craft’sskinandtheaircanalsocreateheat. Detection of IR signatures can give defenders highresolutionoftargetsatshortranges.Infraredwavescanbeattenuated by clouds and other atmospheric conditions,but IRsensorsarepassive,makingthemdifficulttocounter.Heat-seekingmissilesembodytheuseofinfraredforthefinalengagement. Consequently, reducing IR signature is important tosurvivability incertainenvironments.ToreduceIRsignature,stealth aircraft try to mask the tailpipe and engine metalheat.AnadditivemixedwiththeSR-71’sfuellimitedexhausttemperatures.TheF-117andB-2donotuseafterburnersorattainsupersonicspeeds,whichcanincreaseIRemissionsbyasmuchas50times. AnothermeansofreducingIRsignatureistomixcooloutsideairwithhotexhaustairbeforeitleavestheaircraft.Sawtooth trailingedgescancreateshedvortices tomixcoolerambientairwithhotexhaustair.Exhaustscanbeshieldedfromdirectviewthroughtheuseof louversandthrough placement on the top of the fuselage. Stealthalso requires reducing the temperature of the enginesthroughdiversionoflargeamountsofairthroughtheen-ginebay. Eachofthebasictechniquesofsignaturereductionin-volvesacomplextrade-offbetweensurvivabilityandaircraftdesignparameters.OnceanLOaircraftisdesignedandtest-ed,however,itmakesradardetection,tracking,andengag-ingmuchlessefficient,asthenextsectiondemonstrates.

SIGNATURE REDUCTION AND MISSION PLANNING Oncetheprinciplesofradarreturnareunderstood,thenext step is todeterminetheoveralleffectof signature re-duction,andhowitdeliversbenefitsfortacticalmissionplan-ning.Radarcrosssectionvarieswithaspectandwiththefre-quencyof the radarattempting to track it. Bothconceptshaveimportantimplicationsfornettingthetacticalbenefitsofstealth. First,evenalowobservableaircraftwillhavewhatmightbe called its good sides and its bad sides. Since RCS is athree-dimensionalpolygon,thescatteredelectricfieldcanappear as a different shape depending on aspect, effec-

tivelymakingthesignaturelargerorsmallerandtheaircraftmoreorlessvulnerabletodetection,tracking,andengage-ment.Anaircraftpassingthroughtheenemyairdefenseen-vironmentmaybevisible fromseveraldifferentanglesas itapproachesthetarget,attacks,anddeparts.TheRCSofanaircraftwillbedifferentdependingonwhataspectorangletheenemyradarsees. Soundtacticscallforminimizingthelargerradarreflect-ingaspects.Headon,ahigh-performancefighter’sconicalnosewillminimizereturn,butitsairintakesmaycausespec-ular reflection.Wavesmaybediffractedfrombouncingoff

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theintakewallsandfromdiffractioninsidethecockpitarea.Waves will travel along the wings until they are diffractedfromthewingtipsandreturnedfromthetrailingedge.Fromthe side, the RCS will be much larger. The flat plate of thevertical stabilizer presents a large specular reflection, pluscornerandedgediffraction.Pods,ordnance,ordroptanksunderthewingswillalsocauselargerreturns. Theidealforastealthaircraftistoreducethesignatureinallaspects.All-aspectreductionisvaluablebecauseen-emyfightersandground-basedairdefensesmightobservetheattackingaircraftfrommultipleanglesastheaircraftfliesitsmission.However,inpractice,signaturereductionsarenotuniform.Aerodynamic trade-offsalso forcecompromises insignaturereduction. The analysis in this section will examine three differenthypotheticalsignatureshapes.Combataircraftintoday’sin-

ventoryemployanumberofdifferenttechniquesforreduc-ingtheirradarcrosssections.TheFuzzball,Bowtie,andPac-manshapesarehighlysimplifiedsymbolsforbasicpatternsof signature reduction. In thisanalysis, the signature iscon-stantatall frequencies.Actualaircraft signaturesarecon-siderablymorecomplex,andofcourse, informationaboutthemisrestricted.TheintentofthethreeshapesistodepicthowgeneralpatternsofLOreductiongiveattackersarevo-lutionaryedgeinmissionemployment. The Fuzzball signature is a hypothetical shape that isconstantfromallaspects.Theidealshape—theFuzzballwithuniformreductionatallangles—couldintheoryachievere-markableresultsatthelowestlevels. The Fuzzball shape is a theoretical signature that is re-ducedevenly,fromallangles.Itisrepresentativeofthemag-nitudeofdetectionreductionsthatarepossiblewithaper-fectshape—aperfectshapethatprobablywouldnotcon-form to any actual aircraft design. Theoretically, a perfectFuzzballwithauniformlyreducedcrosssectionintherangeof-55dBwoulddenyanyradarreturnatall.Averylowob-servableaircraftcould,ineffect,approachthetargetareafromanyanglewithouttriggeringcrucialcomponentsoftheintegratedairdefensesystem. In reality, aircraft are either designed as LO platformsfromtheoutset,orretrofittedwithmodificationsthatreducespecificaspectsofthesignature,suchasthenose-onRCS.PacmanandBowtiearemorerealisticsketchesofthesig-naturereductionsthatcanbeachievedonceaerodynam-ics and other survivability features are balanced with LOdesign. ThePacmansignaturetypeisasimplifiedapproximationofaconventionalaircraftthathasbeenretrofittedtoreduceitssignatureinthefrontaspectonly. Withincertainparameters,retrofittedmodificationscan


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reduceradarcrosssectionandimprovesurvivability.Apply-ing radar-absorbing material to forward surfaces, shieldinginlets, ducts and canopies, and minimizing ordnance andotherprotrusionsaresomeofthemeasuresthatcan lowerRCS fromthenose-onangle.Rearandsideaspectswouldnotbereducedinthesameway.Thus,inthisnotionalcase,aretrofittedaircraftmighthaveasignaturereminiscentofthecreatureintheold1970sPacmanvideogame. An aircraft designed from the start to be low observ-able can seek to minimize the signature from all aspects.The F-117’s slanted tails, flat bottom, and diamond shap-ingsoughtall-aspectreductionbyremovingoralteringthelargeradarreflectorsurfacesassociatedwithconventional

aircraft.TheB-2,whichhasnoverticalstabilizer,representedanotherstepforwardinall-aspectreduction. However,thelevelofsignaturereductionisstilllikelytobeuneven.Thehypotheticalsignaturetypemaystillbesmallerinfrontandrearaspects,andlargerfromtheside.ThatwouldformsomethinglikeaBowtie,asshownatleft. Tocapturethisconceptinsimplifiedform,thetheoreticalBowtieshapehasa15dBSMreductioninRCSoverfrontandrearaspects.

Signature Varies with Wavelength Foranyofthesignatureshapes,thelowobservabilityofair-craftalsodependsonthewavelengthoftheradarattemptingto detect and track it. Simply put, RCS also varies with wave-lengthbecausewavelengthisoneoftheinputsthatdeterminestheareaoftheradarcrosssection.OnewaytounderstandthisconceptistodepictRCSasequaltothegainofthereturnedradarsignalmultipliedbythereflectingareaoftheobject. Shorterwavelengthswillexcitetransmissionfromasmall-erareaofthetargetobject.Recallthataswavelengthde-creases,frequencyincreases.Asshownpreviously,thelargerwavelengthofalower-frequencywavehitsmoreoftheob-ject.Imaginethatthecrestandtroughofthewavesdefinethesizeofacirclebehindtheobject.Theradiusofthecirclevarieswithsizeofthewavelength.This imaginarycirclede-terminestheamountofpower(calledgain)concentratedinthebeamreturningtothesendingradar.Hence,RCSvar-ieswithwavelength.Foraconstantareaandrange,thedif-ferencebetweenX-bandandVHFwavelengthsresults inadramaticvariationinRCS. Long-range surveillance radars, the first types of ra-

dar invented, emit a long wavelength. Centimetricwavelengths were common in World War II. Higherfrequency radars found in firecontrol radarsand insurface-to-air missiles, have a shorter wavelengthwhichimprovestheclarityoftheirdetectionbutcutstheir range.Thenet result is thatRCSvarieswith thefrequencyoftheradar. Radarsaredesignedtooperateatspecificfrequen-cies to fulfill different functions: long-range surveil-lance, high-resolution tracking, etc. By the same to-ken,“ifaplatformistofacearadarwithknownspeci-fications,thetargetcanbedesignedwiththeradar’sperformance in mind.” Ideally, “if the frequency ofthe radar is known, the RCS reduction effort needconcentrateonlyon the threat frequency.”57As theprinciples of physical optics suggest, aircraft designcanreapgreaterpayoffsinminimizingRCSforhigherfrequenciessuchasfirecontrolradars,thanforlowerfrequenciesemployedbyearlywarningradars. Inpracticalterms,thismeansanLOaircraftcanre-duceitsRCSforearlywarningradars.Butitmaygreat‑ly reduce the RCS for fire control radars that direct

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SAMshots,forexample.Thisdifferencemeansthatalthoughtheenemyairdefensenetworkmayknowastealthaircraftispresent,thenetworkmaynothavethemeanstotrackandengageitwithfirecontrolradars. Degradingtheefficiencyofthesearchradar isthepri-marybenefitofstealth.ThegoalofLOaircraft inatacticalenvironmentistodenytimelyflowofinformationabouttheaircraft’sposition,elevation,andheadingtotheenemy’sin-tegratedairdefensesystem.Thebasicgoalof thisprocessis to reduce the range at which different radars in the airdefensesystemdetectandtracktheaircraft.

The Radar Range Equation Thevalueoflowobservablescomestogetherinasimple

formula knownas the radar rangeequation.The timeatwhicharadardetectsanaircraftdependsonmanyvariables,suchasthepowerandfrequencyoftheradar.However,thesizeoftheradarreflectingareaoftheair-craftitself isanextremelyimportantvariable—andthemajorone thataircraftdesignerscancontrol.Objectswithalargerradarreflectingareareturnmoreenergytotheradarandwillmostlikelybedetectedsooner.Low-eringRCSdiminishestheeffectivenessoftheradarand,ineffect,shortensitsacquisitionrange. The radar rangeequation shows thedrop inde-tectionrangeofagivenradarastheRCSoftheair-craft diminishes. A reduction in RCS does not resultin a proportionate reduction in the range at whicha radar can detect an aircraft, for such measure-mentsdependontheradarrangeequation.Thera-darrangeequationindicatestherangeatwhichanobjectofagivensizewillbedetected.Detectionoc-curswhen the return isabovea threshold specifiedfortheradar. Rangeofdetectionisafunctionofthepowerofthe

sendingradarwavesmultipliedbythesizeoftheradarcrosssection,withthatresultthenaffectedbywavelength.Toex-aminethefirstvariable,thewattageofradarenergysentoutbytheradaraffectshowmanyofthewavesarereturnedtotheantennaareaoffagivenreflectivearea:theRCS.Morewattagewillboostthisnumber;buttheRCSvariablewillcon-tinuetodivideoutasignificantportionof thepotential re-turn. ReducedRCS is theprimevariable in the radar rangeequation for radar detection of range. Changing the vari-ables changes the range. Range of detection varies withthefourthrootoftheresultoftheradarrangeequation.Forexample, the radar range equation can be used to dem-

onstratelogarithmicallythata40percentreductioninRCScausesonlya10percentreductioninthedetec-tionrange.Also,doublingthepoweroftheradaryieldsa19percentincreaseinrangeofdetection. Rangeisnottheonlyimportantmeasureoftheef-fectsofRCSreduction.A lowerRCSalsoreducestheefficiencyoftheradar’stwo-dimensionalsearchareaand,forairborneradar,ofitsthree-dimensionalsearchvolume.Stealthactuallyemergesinthreedimensions.Astheattackingaircraft’sRCSbecomessmaller,itde-gradestheefficiencyofradarsattemptingtotrackitinthreepotentialdimensions. The principles are the same as the radar rangeequation. A radar must receive a return signal of acertain strength to register detection. At the sametime, the radar is assigned to search a given areain a given time with a fixed amount of power in itstransmittingsignal.Asdiscussed,powerisavariableintheradarrangeequation.Whenacertainamountof


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powerisspreadoverafixedareainagivenperiodoftime,the power of the signal returned from the aircraft deter-mineswhethertheradarwilldetectit.Becausethepowerattheradarandthelengthoftimefor itssearchareheldconstant,thelowerRCSmeansthattheradarspendsmoreofitsallottedtimesearchingareasthatproducenoreturn,orwhosereturnisnotabovethethresholdrequiredforde-tectionbytheradar. Asa result, the radar’s searchpatternefficiency isde-gradedinallthreedimensionswhenRCSislowered.Intheex-ampledepictedinthechartabove,thevolumeofair-to-airsearchfora-10dBreductionisjust18percentoftheoriginalefficiency,whenradarpowerandsearchrateareheldcon-stant. The lower the signature, the more the aircraft gains insurvivability:toapoint.Atsomefixedpoint,theradar’spowerwillbesuchabigvariableintherangeequationthatitburns

throughoroverwhelmsthethresholdofdetection.Atthispointtheradarwillpickupenoughreturn,evenfromanLOaircraft,toresultindetection.The radar’s power can increase in two ways. First, theaircraftapproachesveryneartotheradar.Second,theoutputpoweroftheradarcanbeincreased.However,itiseasiertoincreasetheoutputpoweroftheradaratlower frequencies of early warning radars than at thehigher frequencies of fire control radars. Tactically, theattackingaircraftcountsondelayingdetectionbyfirecontrolradarsaslongaspossibleinordertoevadeen-gagement.

Shrinking the SAM RingsAnotherpayoffoflowobservablesisareductionintheamountoftimethecombataircraftissubjecttothefulltracking and engagement capabilities of integratedenemyairdefensesthatfireSAMsorcontrolantiaircraftartillery.AreducedRCScutsthedetectionrangeofthe

radarsthatformtheIADS.Forexample,itmayallowtheair-crafttopenetratefarthertowarditsweaponsreleasepointbefore being detected by long range radar. Then, it mayshrinktherangeofthefirecontrolradaroftheSAM.Shrink-ingtheSAMringsreducestheamountoftimetheattackerspendsinjeopardy. Inthechartatleftbelow,atheoreticalFuzzballsignatureisreducedequallyfromallaspects.Usinganairdefensesim-ulationofanattack ingressandegress,theFuzzball followsamedium-altitude straight-inflightplan foradirectattackagainst a target area that is heavily defended with manymodern,overlappinglong-andshort-rangeSAMs. TheblacklineontopshowsthattheconventionalFuzz-ballisengagedbyfirecontrolmorethan50timesinthissce-nario. However, the number of engagements drops whentheFuzzball’soverall signature is reducedas shownby the

nextthreelines.Attheextreme,radarreturnfromtheverylowobservable(VLO)Fuzzballissosmallthattheshapeproducesnovalidshotsatall. Inthepreviousscenario,theuniformlyreducedFuzz-ball signature shape RCS degraded the efficiency oftheintegratedairdefenseinstages.Thenextsectionex-ploresindetailhowloweringRCSdefeatseachphaseoftheengagementbetweentheattackingaircraftandtheairdefensesystem.

Defeating the Integrated Air Defense System Lowobservableaircraftcangainadvantagesovertheairdefensesystematseveralstages.Eachcompo-nentinanIADSisoptimizedforaspecifictask.Justasanintegratedairdefensehasmanynodesthatmakeitfunction,aircraftwithlowobservableshavemanyop-portunitiestostiflethesystem’sabilitytodetect,track,andengageagainst them. Shortening thedetection

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rangeofacquisitionandfirecontrolradarslimitstheamount,quality,and timelinessof the infor-mationthatisfedtotheairdefensesystem.Withlesstimetoacquire,track,andfireamissile,thedefendersstandmuchlesschanceofshootingdowntheaircraft. The next series of charts depicts whathappens to the components of a notionalthreat system when a single aircraft entersits detection, tracking, and firing area. Thesystem’scomponentsarecalibratedtofunc-tionasshowninthechartatright.Inthewhitearea, the surveillance radar acquires targetsfarther out, then hands them off to the firecontrol radar, as shown in the pale blue line.When the hand-off is completed the systemcan take a valid shot in the area marked inred.Twoadditionalcaveatsare important tohow the system functions. When detectionsets up a valid shot, the surface-to-air missilemust be launched at the aircraft within cer-tainparameters.Also, themissile’s seekermust then lockontotheaircraft.Thischartillustratestheidealfunctionofanotionalairdefensesite. Avalidshotcanoccuranywhereinsidetheredbox.Theorangebandinthemiddle istheDopplernotchofthefirecontrolradar.IntheDopplernotch,theaircraftistooparalleltotheradartotrackviatheDopplereffect.Noengagementispossibleinthenotch.Astheaircraftpassesacrossthecen-terofthesystem,radarscanre-engageitonegress. Thegoalofstealthistopre-emptdetectionandbreakdownthechainofevents.Thisseriesofchartsdepictshowthesystemfailswhenitmustattempttodetect,track,andtakeavalidshotagainstanotionalaircraftwithareducedsignatureshape.Watchfortheredvalidshotareatoshrinkas the overall signature of a hypothetical aircraft shapeis reduced.As the red area shrinks, different color bandsreveal what part of the air defense system has failed toengagetheaircraftatanygivenpointontheingressandegress. Note that these next charts zoom in on a closerrange. Thesignaturelevelsfallintofivecategories.Convention-alisanaircraftwithnosignaturereductionandalargeRCS.LowObservable1(LO1)andLowObservable2(LO2)postu-latelevelsofRCSreductionthatenterthestealthzone,butstillarenotaslowasaircraftmayachieve.VeryLowObserv-able1(VLO1)isahighlydesirableandachievablestateofRCSreduction.VeryLowObservable2(VLO2)isahypotheti-calextremenotlikelytobeachieved,andisusedinonlyonechartforillustrativepurposes. Thebestwaytoillustratetheeffectsofsignaturereduc-tionistostartwithaconventionalFuzzballenteringtherangeatmediumaltitude.Thechartattopleftonthenextpagedi-

agramstherouteofaconventionalaircraft.Theblackarrowrepresents an aircraft flying downrange along the track ofthedashedwhiteline.Thelegendontherightsideindicateswhat part of the air defense system is not able to fulfill itstaskwhentheaircraftreachesthatpoint.Intheyellowzone,theSAMcannotbeproperlyguidedtothetarget.However,intheredzone,theairdefensesystemworksperfectly.Redindicatesthataninterceptislikely,inthiscase,atalmost40kmout.Theredzoneshrinksasthesignatureoftheaircraftshrinks. Thenextchart(p.42,bottomleft)showsthesameflightprofile foranaircraftwith LO1 reduction.The red interceptzonerecedestolessthan30kmout.Inthelightblueregion,itisthehand-offtothefirecontrolradarthatbreaksdownduetothelowobservabilityoftheaircraft. Moresignaturereductionyieldsgreaterresults.WhentheairdefensesystemdoesnotpickuptheLOaircraftintime,itcannothandoff this informationtoothersystemcompo-nents.IntheLO2chart(p.42,topright),thesurveillanceac-quisitionradar isthefirst linktofail intheairdefensechain.Inside 20 km, missile fly-out again poses the problem. Theredzonenowconsistsofanarrowpatchjust10kmfromthethreat. VLO shapes may be able to defeat the system alto-gether.IntheVLO1chart(p.42,lowerright),thesurveillanceradardoesnotacquirethesignatureoftheVLO1Fuzzballuntilitisabout20kmaway.Atthatstage,itisdetected,butthefirecontrolradarcannotpickupthehand-offandac-quire theshape.Consequently,no red interceptzoneap-pearsonthechart. Stealth iscomplete.TheFuzzballshapeisnotdetecteduntil very late, and, at that stage, it cannot be tracked orengaged.


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While the Fuzzball is a perfect and therefore hypo-theticalshape,similareffectsoccurwithamorepracticalapproximation of a real aircraft signature. For example,at first, the Bowtie (represented by the charts on p. 43)withlimitedRCSreductiondefeatstheairdefensesystembyfoilingthefirecontrolradar.However,atthisminimumlevelofsignaturereduction,alargeredinterceptzonestillremains. The next step in signature reduction causes muchgreaterreductionofthreattotheaircraft.Thesurveillanceacquisition radar is fooled. Inanothercrucial step, thefirecontrolradarstrugglestoattainafixintimeastheaircrafttransitsthecrucial20km.Theredzoneappearsaroundthe10kmpoint. The redzone represents realdanger foranaircraftat-

temptingtooverflythetarget.However,thesmallertheredzone,thelesstimetheaircraftwouldspendinit.Employingaweaponwithjustafewkilometersofstandoffrangecouldkeepthisoutoftheredzoneoningress. Major RCS reduction shrinks the red zone again andmakes direct attack much more feasible. As the aircraftegresses,italsofoolstheseekerhomingdeviceinthemissile,asshowninwhiteontheBowtieVLO1chart(p.43).Onegresstheredinterceptzoneisverysmall. Soontheaircraft isagainbeyondtherangewherefirecontrol or surveillance radars can detect and track it. Bysystematicallydefeatingpartsoftheintegratedairdefense,anLOaircraftcanvastly improveitssurvivability.ThismakesaVLOaircrafteligible formissions thatotheraircraftwouldhavedifficultycompleting.

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Tactical Advantages of Stealth The simulations above pitted one aircraft against oneSAMsystem.The realbenefitsof signature reductioncomewhenanattackingaircraft facesmultiplethreats. Inatac-tical scenario, strikingaircraftdonotplan tooverfly theairdefense radars. Instead, pilots plan missions to fly aroundsomethreats,andthroughthelesserthreatstothemaximumextentpossible.Thenextchart(p.44,left)depictsanotionalmissionwhereaircraftmustpenetratedenseairdefensestostrikeatahigh-valuetarget.Intheconventionalstrikechart,airdefensesareplacedsoastoprovideoverlappingcover-ageandsealoffattackroutes. Aircraft attempting to fly this mission would encountermultiplethreatsandspendconsiderabletimeinjeopardy.

Instead, as shown in the chart on p. 44 depicting astealthstrikescenario,lowobservables“shrink”thedistanceforearlywarningdetectionandperhapsmoredramatically,forfirecontrol radar.RCSreductioncan, ineffect,openupnarrowgapsinwhatwasintendedtobeoverlappingSAMring coverage. With careful planning, an LO aircraft cangreatly increase itschancefor survival in theduelwith theground-based air defenders by flying through the gaps incoverage.ThechartshowshowastealthaircraftcanthreaditswaybetweenthedegradedSAMdetectionrings. Whenappliedacrossmultipleradarsites,theeffectsoflowobservablesarecompelling.AllSAMsrequireaminimumamountoftimetodetect, track,andacquireatarget.Theprocess, while relatively fast, still requires several steps. TheSAM must positively identify the target, rotate and elevatethe launcher,prepare themissile,andfire.AllSAMshaveaminimumrangethat isdeterminedbythereactiontimeoftheradarsystemandtheaccelerationandmaneuverabilityof themissile.Reducing the rangeofearlywarningdetec-tionandoffirecontrolradarsyieldstremendousadvantagesbecauseitbreaksthiscycle.

The Benefits of Radar Cross Section Reduction Whatisthepayoffforsignaturereduction?Stealthdoesnotrenderaircraftinvisible,astheprecedingdiscussionhasdemonstrated.Therealityismorecomplex.AchievingalowerRCSdegradestheabilityoftheenemyradartodetect,track,andengageaircraft.Mostsignificantly,lowerRCSshrinksthedistanceatwhichaircraftaredetected. Severalimportantcaveatsareessentialtounderstand-ingtheeffectsofstealth.Acombataircraft’sRCSvarieswithaspectandwiththefrequencyoftheradarattemptingtotrack it. According to theoretical principles, very low fre-


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quencyradarwavesmayoftenbeabletodetectaircraft.However,ifRCSreductionsareoptimizedtothehigherfre-quenciesoffirecontrol radars, significantbenefitscanbeachieved. Inhistoricalcontext, theability to lowervulnerability toradar detection restored enormous advantages to air at-tackers. For a B-17, in World War II, little could be done topreventearlywarning.TheearliertheGermanscoulddetectformationsofB-17sandB-24s,themoreopportunitytheyhadtodirectfightersandantiaircraftfiretowardthem. Loweringtheaircraft’sobservability to radarcanallowtheaircrewtocompletemoreofthemissionbeforebecom-ingvulnerabletoradar-controlledweapons.Thisprovidestheattackertheadvantageofavoidingthethreatandminimiz-ingthetimeinthe“redzone”wheredetectionleadstovalid

SAMshots.Also,stealthenablesattackingaircrafttogetclos-ertotheirtargets.Forexample,shrinkingSAMringsmakestheSAMsiteandthetargetsitattemptstodefendmuchmorevulnerabletoattack. Todayand for the future,airdefenseenvironmentswillvaryenormouslyinthetypeofSAMsandthelevelofintegra-tionemployedbytheairdefensenetworks.For this reason,thecurrentandplannedinventoryofmilitaryaircrafteachhavestrengthsandweaknessesthatdependonthescenar-ioinwhichtheymayheemployed.Theprinciplesofstealthplacegreatemphasisonmissionplanningtoachievemaxi-mumsurvivabilityandeffectiveness.Thenextsectionwillex-ploresurvivabilitytactics:theartofpullingthemostcurrentsurvivabilityoptionstogetherformaximumimpactinthejointcampaign.

LOW OBSERVABLES IN THE OPERATIONAL ENVIRONMENT Low observable aircraft provide enormous flexibility intacticsandmissionplanning.Asaresult,theyexpandtheop-tionsforaircomponentoperations.PlannerswhoseekwaystodestroyimportantbutheavilydefendedtargetsfindthatLOaircraftmitigateriskinthreeways.First,stealthaircraftarefarlesslikelytobeshotdown.Second,theycandestroytar-getsatamorerapid rate,beforetheenemycanmoveorreconstitutevaluablecapabilities.Third,highlysurvivableair-craftcanattack integratedairdefensesdirectlyandearlyon,loweringtherisktolesssurvivableconventionalaircraft. ThefinalsegmentofthisessayexplainshowLOaircraftreduceriskandincreaseeffectivenessinaircomponentop-erations,andwhythisprovidesindispensablebenefitsforthe

JointForceCommander(JFC)).DesertStorm is thestartingpointforanydiscussionoftheoperationalimpactofstealth.ThenextsectionexaminesF-117operationsonthefirstnightofthePersianGulfWartoillustratehowhavingahighlysurviv-ableplatform influencedplanning for theaircomponent’sfirstnightofoperations.

Stealth in Desert Storm Air operations in Desert Storm illustrated that reducedRCScouldindeedenabletheF-117toaccomplishmissionsinairdefenseenvironmentsthatwouldhavebeentoohaz-ardousforaircraftwithconventionalsignatures.ThemissionsflownbytheF-117outlinedtheprincipalbenefitsofandtac-

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ticsfortheuseofstealth.Attheoperationallevel,theF-117illustratedtheroleofstealthintheaircampaignasawhole. TheF-117sdrewthemostdangerousmissionsofthefirstnightofthewarbecausetheirstealthattributesgavethemthebestchanceofaccomplishingthemissionandreturningsafely.Iraq’searlywarningradars,whosecoveragereachedwellbelowtheborder intoSaudiArabia,weredesignedtodetectattackingaircraftastheyapproachedIraqiairspace.Sector operations centers (SOCs) would then coordinatetracksoftheattackers,alertingSAMbatteriesandfightersasthemissionprofilesemerged,asshowninthemapabove. When Coalition aircraft neared their targets, overlap-ping coverage from the fire control radars would ensuremultiplechancestofiremissilesattheattackers.Antiaircraftfirewouldblankettheloweraltitudesandreachashighas20,000feet. Iraq’sairdefensesweresonumerousthatitwasimpos-sibletotakeoutalltheindividualSAMbatteriesthatringedkeytargetswithoverlappingcoverage.TheCoalition’sinitialtask“wastofragmentandeventuallydestroytheIraqiIADS,”recorded DOD’s official report to Congress after DesertStorm.58FragmentingtheIADSwithattacksonspecificnodeslike the SOCs would reduce the efficiency of the informa-tion-dependent system well before its numerous individualelements were destroyed. Reaching the SOCs and otherhigh-priority targetsexposedthefirstwavesofattackers toanextremelydensethreatenvironment.Fivehundredradars

atabout100sitesstoodwatchfortheSA-2,SA-3,SA-6,andSA-8batteries.Alsoincludedintheairdefensesystemwereasmanyas8,000antiaircraftpieces.59

Planners at first considered sending a mix of stealthyF-117sandconventionalF-111FsandA-6swithjammingsup-port to attack targets in Baghdad. The F-111’s long rangeanditsabilitytolaunchlaser-guidedbombscouldknockoutcommandandcontrolandkeyairdefensesites.However,incomputersimulations runbeforethewar,abouthalfoftheF-111FsandA-6swere lost to Iraqiairdefenses,evenwhenstandardelectroniccountermeasureswereemployed.60

On the night of Jan. 17, 1991, two F-117s crossed the


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border well before H-Hour and one attacked the SOC atNukhaybinWesternIraqat0251. AnotherdestroyedthecentralcommunicationsfacilityincentralBaghdad.Sixothersflewtailoredroutesandstruckother targets in Baghdad and other SOCs. Other stealthy“aircraft,” namely the Navy’s Tomahawk Land Attack Mis-siles(TLAMs),andUSAFAirLaunchedCruiseMissiles(ALCMs)launchedbyB-52s,assistedbydestroyingsoft targets.Asapostwar surveydescribed it, theF-117s“flew into,overandthrough the heart of the fully operating air defenses.”61 Bydoingso,theystrucktargetsthatweakenedenemyairde-fensesandmilitarycommandandcontrol,withimportantef-fectsforsubsequentairoperations. TacticsfortheF-117includedcarefulmissionplanningtokeeptheaircraftoutsidethenowmuch-reducedrangeofdetectionoffirecontrolradarsascalculatedfortheF-117’sLOshape.TheF-117flewatnighttopreventchancevisualdetection.Overall,theF-117slogged1,297sortiesinOpera-tionDesert Stormwithno losses.Withnoattrition, the JointForce Air Component Commander (JFACC) was free toemploy theF-117sagainstanyhigh-value target.Asanof-ficialAir Force studyconcluded,“Throughout thewar, theyattackedwithcompletesurpriseandwerenearlyimpervioustoIraqiairdefenses.”62F-117pilotsoftenreturnedwithtalesofheavyanti-aircraftfireovertheirtargets.However,theF-117shad successfully deceived enemy defenses with a combi-nationoflowobservables,carefulmissionplanning,and,onoccasion,supplementarystand-offjamming. TheF-117 strikesdestroyednumerouskey strategic tar-gets.Theyalsocontributed to theoverallaircampaignbyusingtheirenhancedsurvivabilitytoknockoutairdefenses,makingitsaferforconventionalaircrafttoflymissions.AftertheinitialF-117strikesthatopenedthewar,otheraircraftat-tackedinstrikepackagesusingavarietyoftacticstocopewiththemedium-tohigh-densitythreatenvironments. F-117operationsinDesertStormdemonstratedthatdi-rectattacks inheavilydefended regionscouldbecarriedoutbyLOaircraft.“Stealthwasanessentialingredientoftheoriginalstrikeforce,”notedoneanalyst,because“itallowedplannerstoinsertstrikesagainstenemycommandandcon-trolnodes.”63Highlysurvivableaircraftsettheparametersforairoperations in1991.Thenext sectionexplores the roleoflowobservablesandhowtheyyieldastrongtacticaledgeforsurvivabilityduelsofthefuture.

Duels of the Future TherecordoftheF-117sinDesertStormpointedtowardmany futureapplications for lowobservableaircraft in thejoint air campaign. However, future scenarios will not beidenticaltoDesertStorm.HeavilydefendedareasmayhavemoreairdefensesthanIraqdidin1991.Ontheotherhand,anumberofscenarioswillinvolvewhatmightbedescribedasamedium-threatenvironment,whereamixofmobileSAMs

presentsplannerswithadifferenttypeofchallenge.Ontopofthis,strikeobjectivesofthefuturecouldalsovary. Inthissection,simulationsofthreedifferentthreatenvi-ronmentsofthefuturewill illustratehowdifferentlevelsandtypesof signature reductionbecomecontrolling factors inaircraft survivability and in air campaign planning. Thesethree scenarios were studied using a simplified version ofa common air defense simulation model. The objective ofeachscenariowastoportrayhowdifferent levelsofsigna-turereduction improvesurvivability inagivenenvironment.EachenvironmentmirrorsthetypesofattacksthattheJointForceCommandermaycallontheaircomponenttoper-forminthefuture. The three futureattack scenarios,as shownbelow, setupdifferenttypesanddensityofthreats. The Direct Attack scenario simulated a mission into aheavilydefendedregiontoattackahigh-valuetargetsuchasacommandandcontrolcenteroraweaponsofmassdestruction(WMD)storagesite.TheTacticalAttackscenariorana simulationofanattackona target that ispartofafieldedmilitaryforce.Finally,theThreatAvoidancescenariodiagrammed a carefully planned route around known airdefense sites to attack a time-urgent target in an isolatedarea. The simulation itself employed a mission-level modelthat focused on events occurring within the integrated airdefenses. The model captured variables like the decisionsmadebythecommandandcontrolsystem,theallocationandoperationofSAMs,andtheabilityofthevariousradarsineachcomponentofthesystemtotracktheattackerandfireavalidshot.Severalvariablesweresimplifiedinordertoextracttheunclassifiedresultspresentedhere.

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Theresultsproducedameasureofvaliddetectionsthatcould lead to the firing of a surface-to-air missile. Graphsrecorded thenumberofdetections thatwereassessed toleadtoavalidshot.Forthissimulation,onceashotwasfired,theactiondidnot stop.Themodelcontinuedto runsoastorecordthetotalnumberofdetectionsthatcouldresultinshotsfiredateachsignatureshapeoningressandegress.Noattemptwasmadetoassesshowmanyshotsitwouldtaketokill theaircraft,orhowmanymissilestheairdefensesys-tempossessed. Instead,thesimulationsoughttoassesstherelativereductioninnumberofvaliddetectionsleadingtoaSAMshotfordifferentsignaturelevels,countermeasures,andtactics. The next series of charts measures the relative num-bersofvaliddetections leading toSAMfirings fordifferentsignatureshapes.Oneofthemost interestingwaystoviewthedataistotrackthetimeinjeopardyforeachshapeasmeasuredbythetimefirecontrolunitsbegintoregistervalidshots.Twodifferentaltitudesareusedinsomechartstoshowtheeffectonsurvivability.

Direct Attack in a Dense Threat Environment Thefutureequivalentofheavilydefended,vitaltargetcomplexes like Schweinfurt, Hanoi, or Baghdad is likely tobe a capital region. The direct attack scenario posited acityin2010whosekeymilitarytargetsareringedwithover-lappingmodern long-and short-rangeSAMsofamodernIADS. Integrated air defenses are generally positioned soastomaximizetheareaofcoverage.Typically,onlyregionsofmajormilitary importanceareworththefinancial invest-mentofredundant,overlappingcoverage.SAMsarenotsocheapandplentifulthatnationscanaffordtosprinklethemeverywhere. However, where SAM detection rings overlap,thecoverageissodensethat it is intendedtoensureakillagainsttheattackingaircraft. To attack, the aircraft must penetrate to its weaponsreleasepointsevenwiththreatsfromSAMscomingfromallsides.Asthechartonthepreviouspageshows,thedirectat-tackenvironmentexposestheaircrafttonumerousradarsaswouldbeexpectedinanattackonacapitalregionorotherhigh-valuelocation. In this most demanding environment, a conventionalaircraftsignaturesuffersfrombothsustained,earlydetectionandfromagiganticspikeindetectionoverthetargetarea. Thenextchart (top, right) shows theconventionalair-craft signature inblack.Thedashed line represents theat-tackmissionflownat25,000feet. Thesolidblacklineshowsthatflyingthemissionatlowaltitude, about 500 feet, yields some survivability improve-ment,butnotmuch.Thered,green,andbluelinesshowhowperfectsignaturereductionofaFuzzballshapeimprovessur-vivability. More practical signature shapes fare differently in the

directattackenvironment.Asportrayedinthenextchart,aPacman shape with some LO reduction on the nose faresonlyslightlybetterthantheconventionalshape. ThePacmanshapeisdetectedfourminuteslaterthanthe conventional shape. At the 27-minute point, Pacmanshapedetectionsarestilllessthan20,whiletheconventional


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shapehashit30detections.Pacman’sdetectionratespikesdramaticallyto50+detectionsdirectlyinthetargetarea,atthemid-pointinthescenario. Asaresult,thePacmanreductionswouldbeofminimalvaluetothecampaignplanner inthisscenario.Even if thenose-onreductionswillputthatpartofthesignatureintheVLOcategory,thenumberofengagementsremainshigh.Asitfliesawayfromthetargetitexposesthelargeareaswhereits signature isnot reduced.ThePacman shapewouldnothaveagoodchanceofcompletingthemissionsuccessfully.Together, these facts would make it difficult for the JFACCtocountonsendingaircraftwithPacmanshapestoattackheavilydefendednodes.Inallprobability,theJFACCwoulddeviseaverydifferentaircampaignplan that focusedonrollingbackairdefensespriortolaunchingdirectattacksofthissort. However, the Bowtie shapes, withsignificant levels of all-around reduction,displayafunctionalincreaseinsurvivabil-ity.ReducingtheBowtie’sRCShastwoef-fects. First, the aircraft’s time in jeopardydiminishes. Second, signature reductioncausesadropinthenumberofvalidshotsmeasuredbythismodelintheBowtiede-tectioncomparisonchart(p.47). The Bowtie shapes at signature lev-elsLO1andLO2takefarfewershotsfromtheoverlappingSAMsinthisscenario.TheVLO1 signature reduces the number ofshotstakenandspendsonlyabouteightminutes in jeopardy, compared to a full30 minutes for a conventional signatureshapeinthesamescenario. For the air component, the tacticaladvantagesofaircraftwithBowtiesigna-turesarepotentiallyenormous.Frontandrear aspect reduction, especially at thelowest signature levels, greatly increasessurvivabilityagainstoverlappingSAMcov-erage. TheVLO1 shape pounces on theair defenders, not even coming into theregion of vulnerability until it is very nearthetarget.Evenoverthetargetregion,theairdefensesthatrecordedaspikeofmorethan50shotsagainsttheconven-tionalaircraftnowscorejustabove10.Practicallowobserv-ablesdonotmake theaircraft invisiblebyanymeans.Buttheygreatly increaseitsoddsofsuccessanditschanceofsurvivingthistypeofmission. Usingthesamesimulationdata,thechartonthispageindicatestheratiooflong-rangeandshort-rangeSAMstak-ingshotsateachsignatureshape.For thePacmanshape,signature reduction yields only a marginal improvement insurvivability.

SignaturereductionintheBowtieshapediminishesthenumberofshotstaken,whiletheVLO1Bowtieshapescoresaparticularlysharpdrop.

Tactical Attack Environment TheTacticalAttackEnvironment isascenario inwhichtheairdefensesarelessdense,butwherenumeroussortieswillbeflowneitheraspartofpeaceenforcementoperations,oraspartofwartimeattacksonenemy forces in thefield.SAMsystemsandIADScomponentshavespreadthroughouttheworldaspartoftheinternationalarmsmarket.USforcesand Coalition partners are likely to encounter many situa-tions where a mix of air defense systems pose a potentialthreattoairoperationsoveranextendedperiodoftime. Someof themostcriticalanddemandingtypesofair

operations involve attacking fielded military forces. In Des-ert Storm, for example, more than 70 percent of all sortiesflownwereintheKuwaitTheaterofOperations(KTO)againstatactical threatenvironment.Thetacticalattackscenariopostulates an environment where forces on the move willbringwiththemmobile,shorter-rangeSAMs. Because the tactical attack scenario is a less densethreatenvironment,differentsignatureshapeshaveagreat-erchanceofachievingsuccess.Thenextgraph(p.49,topleft)beginswiththesimulatedengagementtrackofacon-ventionalaircraftshape.Whiletheoveralldetectionsarelow-

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erthaninthedensethreatofthedirectattackscenario,theconventionalshapeisstillfiredonforalongperiodoftime.Incontrast,thenose-onreductionofthePacmanshapeisnottracked on ingress until much later. Reducing the nose-onsignaturehelpsprimarilywiththethreatsencounteredastheaircraftfliestowardatarget.Onceinsideacertainrange,thelargesideandrearsignatureareasmaketheaircraftnearlyasvulnerabletoradartrackingasaconventionalshape.TheVLO1Bowtieachievesmuchbetterresults.Fewshotsaretak-enandthetimeinjeopardyisbrief. Pacman’s survivability advantages must he tightly tai-loredtothescenarioinwhichtheycanmakethemaximumcontribution. Nose-on RCS reduction of this type might beusefulwhenanaircraftispartofapackageperformingle-thalSEADthatintendstoknockoutfirecontrolradarsbeforeturningtoegressandexposingthelargesignatureareas.At-tritionriskswillstillbehigherforthePacmanshapethanfortheBowtieshape.However,theprospectsforsuccessfulem-ploymentareimproved. Altitude is another tactical consideration. The chartaboveleftrepresentedthetacticalattackscenarioatme-dium altitude, about 25,000 feet. Survivability improved forboththeconventionalshapeandthePacmanshapewhentheaircraftattackedatalow500-footaltitude(chartaboveright).FortheVLO1Bowieshape,altitudedoesnotmakeasignificant difference in this scenario. The lower, more bal-ancedsignatureismoresurvivable. Compared to balanced signature reduction, nose-onsignaturereductionillustratedbythePacmanshapehasitslimits.Eveninthetacticalenvironment,withaVLO1levelofreduction,wherethePacmanshapeperformedbest,ithasasignificantprobabilityofdetectioncomparedtofullorpar-tialall-aspectreduction.Thechartatrightrevealstherela-tivedifferences. Evenatlowlevels,thelackofsignaturereductioninar-eas other than the nose-on aspect begins to corrode thePacmanshape’ssurvivability.Lowaltitudewillalsoholddense

antiaircraftgunthreats.InVietnam,morethan85percentofaircraftwerelosttoantiaircraftfire.InDesertStorm,aircraftintheKTOreportedsporadicdenseantiaircraftfireandshotsfromhand-heldinfraredSAMs,evenaftertheIADShadbeenreduced to almost zero effectiveness. The survivability ad-vantagesoflowaltitudemissionsmustbebalancedagainstthelevelofthreatfromopticallyguidedantiaircraftfire,smallarmsfire,andhand-heldSAMs.

Threat Avoidance Similar resultsapply inanother scenariowhere theair-craft attacks a point target along a flight path that delib-erately minimizes exposure to the fire control radars. Thethreatavoidancescenarioreliesonmaximumuseoftacticsthrough a carefully planned flight path where the aircraftskirts the edges of the anticipated radar coverage areas.ThreatavoidanceissimilartowhattheF-117didonitsopen-ingnightattackon theH-2airfield,aScud launchsite.Be-causelowobservablesreducetherangeofdetection,theSAMringsshrink,makingtheprospectof“threadingthenee-dle”thatmuchbetter.


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The threat avoidance scenario presents convincingevidencethatbalancedsignaturereductioniswhatmakestacticsandplanningmosteffective.ThenextchartillustratesthattheshotstakenagainstaconventionalshapeandthePacmanshapearestillhighinnumberevenwithrouteplan-ning.

A real contrast emerges when the simulation sends intheBowtieshapes.EvenwithonlyanLO2levelofsignaturereduction,theBowtienetsenormousimprovementinsurviv-ability.AttheVLO1level,theBowtieexperiencesonlyafewvalidtrackingsbythefirecontrolradars. ForthePacmanshape,whathelpsmostisloweraltitude.Asdisplayedinthechartbelow,thesignatureshape’srunatlowaltitudeminimizestimeinjeopardyanddecreasesover-allshotstaken. The threat avoidance scenario confirms that low ob-servablesareessentialtoassuredmissionsuccess.InDesertStorm, there were some targets where the threat allowedlowaltitudeattacksbyconventionalaircraft.However,anti-

aircraftfirewasafactorandmostattacksmovedtomediumaltitudesasaresult.Forexample,BritishTornadoesflewlowlevelattacksagainstIraqiairfieldsandexperiencedsomeofthehighestlossratesofthewar. Asseeninthechartbelow,varyingaltitudeisnotnearlyas effective for survivability as reducing the signature. Theresults of the simulation suggest that flying at high altitudedrawstheaircraftoutoftherangeofsome,butclearlynotall,SAMs. However,therealmessageofthischartisthatsignaturereductionenables theaircraft toplana route thatgreatlyincreasesthechancesofsurvivability.ThevariationfromLO1toLO2issignificant,whiletheVLO1shaperesultsindramaticimprovementtoaveryhighchanceofsurvival.

Thetacticalflexibilityoflowobservablesisindispensableto futuremissionplanning. In future scenarios,highly surviv-able aircraft will draw the assignments to attack heavilydefendedhardenedtargetsthatcanonlybedestroyedbydirectweaponsreleaseof largepenetratingbombs.Keep-ingattrition toaminimumwillbe importantbecause itwillensure that the air component can continue to generatesortiesanddeliverordnanceattheratedemandedbytheJFC’s objectives.Another major payoff of highly survivableaircraftwillbetheirabilitytoensurethattheaircomponentcan attack important targets from the outset and destroythosetargetsrapidly.

Stealth and Electronic Countermeasures Theduelsof the futuremayalsodrawonacombina-tion of stealth and ECM to improve aircraft survivability inspecific scenarios.A conventional aircraft cannot operatesafely in a high threat environment until the integrated airdefensesystemisnearlyimmobilized.Intheory,anextremely

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lowobservableshapecouldbesurvivableinalmostanyenvironment.However,planningforthemajorityofairoperationsfallssomewhereinthemiddleofthatspectrum.Asthreatradarsexpandtheircapabilities,stealthandECMhavea role toplay inworking to-gether to increase aircraft survivability—especiallywhen prompt attacks on key nodes have reducedtheefficiencyoftheenemyIADS. Insomescenarios,ECMcanalsoprovideaddi-tionalassuranceforLOaircraftagainstcertaintypesof threats.While analysts have established that theF-117sdidnotbenefitfromECMsupportfromEF-111sonthefirstnightofthewar,recordssuggestthattheadditionaluseoftheEF-111waswelcomedbyF-117crewsinsubsequentmissions. Foraircraftwithout theF-117’s signature reduc-tion,or foraircraftoperating indifferent threatenvi-ronments,ECMcancontributesignificantlytosurviv-ability. Conventional aircraft return much larger sig-natures.ECMislimitedbythepoweroftheairbornejammer.Therefore,asmalleraircraftRCSiseasiertocloakbecauseitrequireslesspowerfromthejammer.Anaircraftthatreducesitsfront-aspectsignaturebyafactorof10cutsthenotionaldetection range by 44 percent. The power required in theECM jammer also decreases in proportion. For the sameamountofpower,ECMcanjammoreeffectively. Thenextseriesofchartsdescribestheresultsofasimula-tionthatillustratestheinteractionofreducedRCSandECM.ThesimulationpairedtheFuzzball,Bowtie,andPacmansig-naturereductionshapeswithatoweddecoyandassessedtheresults. ToweddecoysareaformofECMthatiscarriedoutsidetheaircraft.Atypicaldecoyisunreeledfromtheaircraftoverthe main threat area. Because the small pod is towed bytheaircraft,thecoverageofitstransmitterisnotblockedorimpairedbytheaircraftitself.Toweddecoysprovideagreaterarcofcoveragearoundtheaircraft thanwouldanECMpodbeingcarriedonaweaponssta-tion. Thechartattoprightplotsthequalitativesurviv-abilityforaBowieshapeatthreedifferentsignaturelevels.Ontheleft,thescenarioisdirectattack,whileon the right, the threat avoidance scenario is por-trayed. As the chart demonstrates, the VLO1 level ofRCSreductionpairedwithatoweddecoyproducesonly a“good” level of survivability in this conserva-tiveanalysis. In this scenario,aweaponwith limitedormoderatestandoffwouldprobablyimprovesurviv-ability.Whenthethreat ischanged,atoweddecoycanimprovesurvivabilitysignificantlyfortheL02Bow-tie.Still,onlyVLORCSreductionproducesdesiredre-sultsof“verygood”survivability.

Toweddecoyscanbeofevenmorebenefittomoder-atelystealthyaircraftwhenearlierattackshavealreadyde-gradedtheairdefenses.Thisscenarioisimportanttoexplorebecause it representsplanningfor theuseofamixofVLOaircraftandaircraftwithmoderatestealthretrofits. Thechartbelowplotsqualitativesurvivabilityasafunc-tionofLOshape,ECM,andthestateoftheairdefensesys-tem.Atthetopofthechart is thesurvivabilityzone,wherethe probability of survival is rated very good. In the surviv-abilityzone,theprobabilityofsurvivalishighenoughtokeepattritionrateswithinacceptablelevelsforasustainedcam-paign. In turn, reducing the efficiency of the air defense sys-temorotherhighvaluetargetsopensupmoreoptions fortheemploymentofotheraircraft.Forexample,highlysurviv-ableaircraftcanattackkeynodestodegradetheIADSto50percent,25percent,orevennear-zerolevelsofefficiency.


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Thisdoesnotmeanthat50percentor25percentoftheearlywarningradars,firecontrolunits,andantiaircraftgunsaredestroyed.Rather, itmeansthattheflowofdetectionandtrackinginforma-tionisdegradedtothepointwheretheIADScanreacttoonlyabout50percentofwhatisactuallyoccurringinthebattlespaceitissupposedtopro-tect. The lines each represent one type of LOshapeassimulatedatagivenaltitude.Thehori-zontalaxishassixpoints.Inthefirstthree,noECMdecoyisdeployed. As the IADS becomes less efficient, ECM isbetterable to improve survivability rates.As thefarrightsideofthechartsuggests,aconvention-alaircraft,oronewithsomeLOreduction,couldbegin to function efficiently when it employs adecoyandoperatesinareaswheretheIADSareat25percentefficiency.This,infact,isexactlythetypeoftacticalenvironmentthataircampaignplannerssetouttocreatebysendinghighlysurvivableaircrafttodestroyselectedairdefensenodes. Thetacticaloptionsliebetweenthesetwoextremes.AsignaturewithsomelevelofLOreduction,plusatowedde-coywithECM,improvesitssurvivabilitysomewhat.TheVLO1shape,whichcontainssubstantiallowobservablesinitsde-sign,reachesthesurvivabilityzoneinthehighestthreatenvi-ronmentonlywhenadecoyisincludedandtheairdefensesaredegraded. Inthethreatavoidanceenvironment(showntopright),the importanceofcampaignplanning todegrade theairdefenses standsout.TheVLO1shapeachieveshighsurviv-ability with or without the decoybecauseitssmallRCSenablesittothreaditswaybetweenthethreatrings. However, the conventionalshape and the moderately re-duced LO1 shape operate mosteffectively when the IADS is de-graded and a decoy is present.A Fuzzball achieves a very goodprobability of survival at the LO2level whether the IADS are de-gradedornot. Inpractice, thisanalysiscon-firmswhatplannersalreadyknow.AircraftwithoutsignificantRCSre-duction would be scheduled toattacklaterinthecampaign,andtowed decoys will improve theirsurvivability and effectivenessrates.

Thescenarioandthethreatenvironmentmatteragreatdealevenwhen lowobservablesandECMarecombined.In the chart below, the Bowtie atVLO1 runs through eachscenario. Inthethreatavoidancescenario,asshownearlier,ECMmakesnodifference.However,inadirectattack,ECMgreat-ly increases the Bowtie’s chances of surviving. ECM is alsohelpful in thetacticalattackenvironmentwheresustainedoperationsmightotherwiseproduceunacceptableattritionovertime. Theanalysisof lowobservablesandECMunderscorestwo important points. First, depending on the aircraft andthe scenario threat environment, tactics will dictate differ-ent combinations of systems to ensure survivability. Many

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Theradargamehasdefinedandredefinedthetacticsfor air combat since 1940. Aircraft survivability surfaced asa controlling variable in the effectiveness of air operationsinWorldWar I. The quest for survivability immediately influ-enced new aircraft designs, and contributed to the emer-genceofspecializedcombataircraft.FromtheSpadsandFokkers honed for pursuit, to the Gotha bombers and theSalmsonarmoredtrenchfighters ladenwithguns, thegoalwasincreasedsurvivabilityinthethree-stageduelofdetec-tion,engagement,andprobabilityofkill. On the eve of World War II, the invention of radarchanged the detection problem almost overnight by ex-pandingdetectionrangesfromthelimitsofthehumaneyetoreachesofmorethan100miles.Overthenextthreede-cades,radarcametodominateeachstageoftheduel.In-tegratedairdefenseswithradar-guidedmissilesthreatenedthedeathoftheflyingairforcesunlesstacticsandcounter-measurescouldcompensate.Researchonelectroniccoun-termeasuresand thepackagingofaircraft formutual sup-port constituted the primary defenses against proliferatingairdefensecapabilities.

scenariosinthefuturemayfeaturearelativelymoderateairdefense threat. In thosescenarios,aircraftwithmoderatelyreducedsignatures(suchascanbeproducedbyretrofittedLOmodifications)maybeabletooperateeffectivelyincon-junctionwithtoweddecoysandotherECMsupport. The second point, however, is that highly survivableaircraft are the air component commander’s best tool toshape the environment for air operations. Other scenarios,withdenserandmoresophisticatedairdefensethreats,willdemand ever-improving results in signature reduction. Thedensestthreatssuchasthosepresentedbyacapitalregionwillstillinvolveameasureofriskthatisbestmitigatedbylowobservables. For this reason, low observables are the“jewel in thecrown” for aircraft survivability in the operational environ-ment. Balanced, all-aspect signature reduction is the mostimportant advantage an aircraft has in the duel with thedefendingIADS.Onlyaircraftwiththosespecialsurvivabilityattributescanattack the IADSwithmaximumefficiency. Inturn,lowobservablesalsoenhanceothersurvivabilitymea-sures. Electronic countermeasures are better able to maskanaircraftsignaturethathasalreadybeenreducedbylowobservables. Tacticalsurvivabilityadvantagesadduptooperationalresults. The options for employing airpower are regulatedby the duel between attackers and defenders. Survivabil-

ity shapes theoutcomethatcommanderscanplan forastheyconstructtheaircampaignanddeterminewhatitwillcontributetotheJFC’soperational-levelplans.Thenumberofhighlysurvivableaircraftisthemajorvariablethatdeter-mineswhatcanbedoneinthecrucialearlyhoursanddaysofaconflictagainstanadversarywithairdefenses. In Desert Storm, for example, highly survivable F-117stealthfightersallowedtheJFACCtoattackmultipletargetsetsinthefirsthoursoftheairwarinsteadofwaitinguntiltheintegratedairdefenseswerecompletelysuppressedalmostaweeklater.Stand-offweaponssuchasTLAMswereimpor-tant,buttheirinabilitytodestroyhardtargetsormobiletar-getslimitstheirutility,especiallyinsustainedoperationsoveralargetargetset. Campaignsofthefuturewilldependonstealthtode-gradeenemyairdefensesanddestroyotherhighvaluetar-getsthroughimmediateattacksonkeynodesinthesystem.Itisthisabilitytoshapetherestoftheaircomponent’sop-erationsthatmakeslowobservable’sthejewelinthecrownfor airpower. Highly survivable aircraft are the instrumentsthatensurethateventhemostheavilydefendedtargetsinfuture threat environments will be within airpower’s reach.TheygivetheJFACCtheabilitytocontroltheairandcontrolwhatwillheattackedfromtheairalmostfromtheoutset—aluxuryimaginedbyWorldWarIIaircommandersonlyintheirdreams.

CONCLUSION: THE FUTURE OF STEALTH

By the 1970s, winning the radar game had becomethe central ingredient in dominating the skies. Developingand testing low observable features for aircraft offered amorecertainway tobreak thecycleofconstantlyadjust-ing electronic countermeasures and counter-countermea-sures.More thanadecadeafter its initial testing, theF-117provedthevalueandflexibilityofstealthdesignbycomplet-ingdirectattacksonheavilydefendedtargetsduringDesertStorm.TheJFACCwasabletousethehighlysurvivableF-117todestroytargetsatamorerapidpace,andwithmuchlessrisk,thancouldhavebeenexpectedwithconventionalair-craft. Lowobservablesinaircraftdesignrepresentanachieve-ment in bringing complex analysis and prediction of thecauses of radar return together with aircraft design princi-ples.Theprinciplesandthetrade-offsrequiredtoachieveanLOaircraftdesignarecomplex.Lowobservablesdonotnul-lifyradarorrenderaircraftinvisible.Instead,LOdesignseeksto control and direct radar return, thereby diminishing theoverallradarcrosssectionoftheaircraft.Muchoftheeffectisachievedbycurtailingspecularreflectionanddiffraction.


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Asmajorsourcesofreturnarelessened,designsseektocon-trol travelingwaves,cavitydiffraction,andtoeliminatesur-faceimperfectionsthatcouldproducereturn.Balancedlowobservables include all-aspect signature reduction pairedwithattentiontoothersourcesofelectromagneticsignature,fromvisualandacoustictoinfrared.Advancedlowobserv-ablesalso require striving forcontrolofallelectronicemis-sionsfromtheaircraft. Onceachieved,aircraft signature reductionproducesdramatic tactical results. Signatures vary according to thefrequencyof thesearch radarandtheaspect fromwhichitviewstheaircraft.However,reductionsinRCSimmediatelybegintocutintotherangeatwhichradarscandetectair-craft.A choice to optimize combat aircraft to be low ob-servabletofirecontrolradarsbreaksacruciallinkintheairdefensechain. LOaircraftaredetected laterand trackedwith greater difficulty, allowing them to spend less time injeopardythanwouldaconventionalaircraft.Inturn,thistac-ticalflexibilityproducesenormousoperationaladvantagesfortheaircomponent. Aslongastheradargamedetermineswhocontrolstheskies, lowobservableswilldelivervitaladvantages.ThePer-sianGulfWar,themostdifficultairdefenseenvironmenten-counteredinmilitaryoperationsinthe1990s,demonstratedthathavinghighlysurvivableaircraftallowedtheaircompo-nenttoachieveavarietyofobjectivesquickerandwithlessrisk.Futurecommanderswillalsocountontheabilitytokeeptheupperhandintheradargame.

Counters to Stealth? Becausestealthissoimportanttocurrentairoperationsand military strategy, it is reasonable to ask if and when itmightbeeffectivelycountered.Historianscontendthatev-erymilitaryinventioninhistoryhasbeencounteredbynewinventionsortactics, induetime.Theradargameillustratesthisprinciple,too.Radarchangedthesurvivabilitydueldur-ingtheBattleofBritain in1940.Stealthchangeditback50yearslater,inthePersianGulfWarof1991.Themostrelevantquestiontoaskisnot“canstealthbecountered?”but“howdifficultisittocounterstealthwithknowntechnology?” TheradarrangeequationthatdemonstrateshowlowerRCS reduces the range of detection contains several vari-ables.Tocounterstealthwithamonostaticradar,theairde-fense radarwouldhave togreatly increase itsgainat thereceiver. The way to do this would be to greatly increasethe power of the system. If the target aircraft had an RCSreductionof1,000,theradarpowerwouldhavetoincreaseby a factor of 1,000 to detect it at the same range as anon-stealthyaircraft.However, increasingpower iseasieratlongwavelengths,notattheshort, rapidfrequenciescom-monly used for fire control. Ultra-wide band radar poses asimilarproblem.Anultra-widebandpulsecouldemitwavesatseveraldifferentfrequencieshopingtocatchthestealth

aircraftataweakpointinitsRCSreduction.Buttransmittingoverawidebanddiminishesthepowerineachband,cut-tingtheefficiencyoftheradar. Thesecondissueindiscussionsofcounter-stealthisthatstealthaircraftaredesignedagainstmonostaticradars,thetypeusedinnearlyallmilitarysystems.Monostaticradarcou-plesthetransmitterandreceiveratthesameplace,apro-cessthatsimplifiesthecrucialfunctionofdistancetracking.Intheory,abistaticradarthatplacedthetransmitterinonelocationandthereceiverinanothermightbeabletopickupwhatmightbecalledthe“craning”RCSthatisdirectedawayfromthemonostaticradar. However,“bistatic radars, while simple in concept forthedetectionofstealthyvehicles,havemanyfundamentaltechnicalandoperationalissuestoovercome,”accordingtoJohnShaeffer,RCSengineeratMariettaScientificinGeorgia.The receiver antenna beam must intercept its companiontransmitbeamand follow the transmitpulsewhich ismov-ingatthespeedoflight.Unlessthetransmitterandreceiverpulses are synchronized, distance measurement is impos-sible.Evenaworkablebistaticradarmustthenaddresstheproblemofhowmuchvolumeofairspaceitcanscanatagivenpowersettinginagiventime.Whenthereceiver,trans-mitter,andtargetarelocatedonastraightline,thereceivercanbeoverwhelmedbythetransmitterpulse,whichhidesthetarget’s radar return.AsShaefferput it,“This is similar tolookingintothesunforlightscatteredfromVenus.”64

TheRCSreductionofstealthaircraftisdifficulttocoun-ter.Improvementsinradarmustgoaverylongwaytomatchthe performance they were designed to achieve againstnon-stealthy aircraft. Concerns about countering stealthshouldpale incomparison to thoseabout theknownandincreasingthreatstoconventionalaircraft.Thedaywillprob-ablycomewhenreusablehypersonicmilitaryspaceplanesreplacejetsastheprimaryvehiclesforensuringaerospacedominance.Untilthen,foraslongasjetaircraftofferthemostreliableoptionforairsuperiorityandairattack,stealthwillbeindispensable.

Improving Future Survivability and Effectiveness The first operational stealth aircraft, the F-117 and theB-2, demonstrated the feasibility of low observables andtheir importanceto rapidandeffectiveairoperations.Likeallcombataircraft, they relyon tactics to reachpeak sur-vivability,andtheyhavelimitationsthatmustberecognizedtoensureproperemployment. Forexample, theF-117andB-2 operate primarily at night. Indeed, many conventionalaircraft do the same to maximize survivability under someconditions. Several developments will make highly survivable air-craftevenmoreeffective.TheF-117’sabilitytodeliverLGBswasacrucialcomponentof itseffectiveness.Recently, theB-2hasdemonstratedgreataccuracywith theGPS-Aided

55


TargetingSystem(GATS)fortheGPS-AidedMunition(GAM.)Theabilitytodeliver16independentlytargetedweaponsinanyweather representsa formidable force. In thenear fu-ture, thedevelopmentofsmallmunitionswillenableallair-craft tocarrymoredestructivepower.Testing isunderwayon 250-pound, 500-pound, and 1,000-pound bombs thatpack the explosive force of the 2,000-pound bombs in to-day’sinventory.Whenstealthaircraftcandelivermoremuni-tionsearlyinthecampaign,theywilltakeupanevengreatershareoftheaircomponent’stasks. Inthe21stcentury,theAirForce,Navy,andMarineCorpsallplantotakedeliveryofnewaircraftthatincorporatelowobservables. With low observables as the centerpiece, arangeoftechnologieshelpsextendmissionplanningoptionsandcreatesthetacticaledgethattranslatestogreateref-fectivenessandflexibilityinairoperationsfortheJointForceCommander. TheF-22,inparticular,mayfillmultiplerolesassurvivabil-itydemands increase. Itwillbe thefirst stealthaircraft thatachievesadominantair-to-air role.However, itwillalsofindanexpandingfunctionasahighlysurvivablevehicleforde-livering advanced air-to-ground munitions—munitions thatcould be used against SAMs or heavily defended targets.Thetrendtowarddevelopmentofsmallerbombswillmaxi-mizetheF-22’sinternalcarriagecapacity.AspremiergroundattackaircraftsuchastheF-15EandtheF-117age,anF-22armedwithsmallmunitionsnowindevelopmentcouldtakeupthemantleofthesurvivableattackplatform. TheF-22willalsohavethedistinctionofbeingthefirststealthaircraftcapableofoperatingduringtheday.Ofallthepossible“counters”tostealth,perhapstheonethatpos-esthegreatestthreattoaircraftsurvivabilityisthetrade-offinspeedandperformance.TheF-22restorestheaerodynamic

advantagesofanairsuperiorityfighter,whiledeliveringthepenetration and bomb-dropping capabilities of the F-117.ThecombinationoftheseabilitieswillpositiontheF-22tobe-come the backbone of air-to-air and air-to-ground opera-tionsrangingfromfirst-nightattackinmajortheaterwarstoairdefense.

Finis Theairoperationsoftheearly20thcenturywentfrombeingausefulsupportingforcelateinWorldWarItobe-ing“adeterminingfactor”intheplanningandexecutionofoperationsinWorldWarII.Itcomesasnosurprise,then,thatwhentheradargamebegantoputtheefficiencyofairoperationsinjeopardy,scientistsandairmenrespond-ed with vigor. The radar game is one that aircraft mustplaytomaintaincontroloftheskiesandthefreedomtoattackanddefend.The joint forcehascountedontheirabilitytowinthatgamesinceWorldWarII.

Winningtheradargamehasbeenandwillremaincentraltofuturejointoperations.AstheUSmilitarymovesawayfromdecadesofplanningforamajorwarinEurope,thenationalmilitarystrategystillcallsfortheabilitytoin-tervene in regional conflicts that will vary in scope andintensity. Intervening on favorable terms will continue torequiretheaircomponenttotakedirectandimmediateaction to control the air and the surface below. Air de-fensethreatshaveincreasedthroughoutthe20thcenturyandwillcontinuetodosointhe21stcentury.Stealthisnomagicpanacea,buttheedgeitoffersintheradargameisindispensable.PairedwithotheradvantagesfromECMto advanced munitions, the effects of low observablesmultiply, and will keep the edge of America’s airpowersharp.


56

1.“NotesontheCharacteristics,Limitations,andEmploymentof the Air Service, 1919,” Maurer Maurer, ed., The US Air Service in World War I, Volume II,“Part IV Postwar Review”(Washington,DC:OfficeofAirForceHistory,1978)p.309-310.

2. Lt. Col. William C. Sherman, USAF, “Sherman: TentativeManual forEmploymentof theAirService,1919,” inMaurerMaurer,ed.,VolumeII,PartIV,p.401.

3.LeeB.Kennett,The First Air War, 1914‑1918(NewYork:TheFreePress,1991)p.45.

4.WilliamMitchell,Memoirs of World War I(NewYork:RandomHouse,1960)p.145.Mitchellfirstpublishedthememoirin1928.

5.Mitchell,p.83.

6. EdwardV.Rickenbacker,Rickenbacker (EnglewoodCliffs,NJ:Prentice-Hall,1967)p.145.

7.Maj.GeorgeE.A.Reinburg,C.O.2ndDayBombardmentGroup,inMaurerMaurer,ed.,The US Air Service in World War I, VolumeIV, “Part1:LessonsLearned:Reports”(Washington,DC:OfficeofAirForceHistory,1979)p.84-85.

8.QuotedinKennett,The First Air War, p.108.

9.LeeB.Kennett,“Developmentsto1939”inBenjaminFranklinCooling,ed.,Case Studies in the Development of Close Air Support (Washington, DC: Office of Air Force History, 1990)p.24.

10.Kennett,“Developmentsto1939,”p.39.

11.Reinburg, p.86.

12.Reinburg,p.86.

13.Sherman,p.369.

14.Sherman,p.370.

15.Spaatzletterof2January1931,quotedinDavidR.Mets,Master of Airpower: General Carl A. Spaatz (Novato, CA:PresidioPress,1988)p.85.

16. David Pritchard, The Radar War: Germany’s Pioneering Achievement, 1904‑45 (Wellingborough, Northamptonshire,England:PatrickStephens,Ltd.,1989)p.64.

17.MatthewCooper, The German Air Force, 1933‑1945: An Anatomy of Failure(London;NewYork:Jane’s,1981)p.135.

18. Impact: Strategic Air Victory in Europe, Vol. III,No.7,July1945, (Washington, DC: Office of the Assistant Chief of Air

Staff,Intelligence)p.9(reprintedinBook7ofaneightbookcollection:The Army Air Force’s “Confidential” Picture History of World War II (NewYork:JamesPartonandCompany,Inc.,1980).

19.Lt.Gen.JamesH.Doolittle,USAF(Ret.),Essay2:“DaylightPrecision Bombing,” The Army Air Force’s “Confidential” Picture History of World War II, Book 6 (New York: JamesPartonandCompany,Inc.,1980)p.xv.

20. In fact, the Germans already had chaff, which theycalledDüppel,thoughtheytoofearedusingit.In1942,uponhearing of the results of a test of Düppel, Göring orderedthatallcopiesofthereportbedestroyed.Watson-Wattalsoopposed the introductionofWindow,claiming thathedidnotwanttoseehisradaradvantagedestroyed.Johnson,p.116-117.

21.BrianJohnson,The Secret War(London:BBCPublications,1978)p.118-119.

22.AdolfGalland,The First and the Last: The Rise and Fall of the German Fighter Forces, 1938‑1945,translationbyMeryvnSavill(NewYork:HenryHolt&Co.,1954)p.202.

23.Johnson,p.118-119.Japaneseradar,operatingat lowerfrequenciesthanGermanradar,required400-footlengthsofthinaluminumtape.

24.J.A.Boyd,D.B.Harris,D.D.King,H.W.WelchJr.,eds.,Electronic Countermeasures (Los Alto, CA: Peninsula Publishing, 1978)p.2-16to2-19.

25.Johnson,p.113-117.

26. Robert Buderi, The Invention That Changed the World (NewYork:Simon&Schuster,1996)p.214-217.

27. Buderi, p. 214-217. August Golden Jr., Radar Electronic Warfare (Washington,DC:AmericanInstituteofAeronauticsandAstronautics,1987)p.2.

28.Cooper,p.130.

29. Impact: Strategic Air Victory in Europe, Vol. III, No. 7,July1945,p.65(reprintedinBook7ofThe Army Air Force’s “Confidential” Picture History of World War II.)

30. Impact: US Tactical Air Power in Europe, Vol. III, No. 5,May1945,p.17(reprintedinBook7ofThe Army Air Force’s “Confidential” Picture History of World War II.)

31.LarryDavis,Wild Weasel(Carrollton,TX:Squadron/SignalPublications,1986)p.6.

32.RobertFrankFutrell,Ideas, Concepts and Doctrine: Basic

END NOTES

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Thinking in the US Air Force, 1907‑1960, Vol.I(MaxwellAFB,AL:AirUniversityPress,1989)p.485.

33.WaltonS.Moody,Building a Strategic Air Force(Washington,DC:USGPO,1996)p.104-105.

34.Moody,p.106.

35.Moody,p.422.

36.Gen.ThomasD.White,quotedinFutrell,p.514.

37. Fletcher Knebel, “The Coming Death of the Flying AirForce,”Lookmagazine,Oct.1,1957.

38. Quoted in Ben Rich and Leo Janos, Skunk Works: A Personal Memoir of My Years at Lockheed (Boston: LittleBrown,1994)p.147.

39.QuotedinRichandJanos,p.247.

40.Futrell,Ideas, Concepts and Doctrine: Basic Thinking in the US Air Force, 1961‑1984, Vol.II,p.389.

41. Gen. William W. Momyer, USAF (Ret.), Airpower in Three Wars (Washington, DC: Department of theAir Force, 1978)p.125-126.

42. Lt. Col. James R. Brungress, USAF, Setting the Context: Suppression of Enemy Air Defenses and Joint Warfighting in an Uncertain World (MaxwellAFB,AL:AirUniversityPress,1994)p.11.

43.Maj.A.J.C.Lavalle,USAF,gen.ed.,The Tale of Two Bridges and the Battle for the Skies Over North Vietnam, USAFSoutheastAsiaMonographSeries,Vol.1,Monographs1and2(Washington,DC:OfficeofAirForceHistory,1976)p.152.

44.Brig.Gen.JamesR.McCarthy,Lt.Col.GeorgeB.Allisonand,Col.Robert E.Rayfield,gen.ed.,Linebacker II: A View From the Rock,USAFSEAMonographSeriesVol.VI,Monograph8(Washington,DC:OfficeofAirForceHistory,1985)p.173.

45.Werrell,p.52-53.

46. Capt. Robert E. Wolff, USAF, “Linebacker II: A Pilot’sPerspective,”Air ForceMagazine,September1979,p.89.

47.Maj.CalvinR.Johnson,“ProjectCHECOReport:LinebackerOperations,September -December1972” (HickamAFB,HI:Hq.PacificAirForcesOfficeofHistory,1978)AppendixFive,p.95;Wolff,p.89-91.48.Col.JohnA.WardenIII,USAF,The Air Campaign: Planning for Combat(Washington,DC:Pergamon-Brassey’sInternationalDefensePublishers,1989)p.60.

49.Brungress,p.28.

50.Quoted inMaj.WilliamA.Hewitt,“Planting theSeedsofSEAD: The Wild Weasel in Vietnam” (Maxwell AFB, AL: AirUniversity,1992)p.34.

51. Lt. Gen. Joseph W. Ralston, Keynote Address to HAVEForum,1994,USAirForceAcademy.

52. William Green, The Warplanes of the Third Reich (NewYork:GalahadBooks,1986)p.247-251.TheBritishalsohadawooden(butnotcompositeandcharcoal-coated)bomber,theMosquito,thoughitsstealthcharacteristicswerealmostnilbecausetheradarwavesthatpassedthroughthewoodouter structurewould reflectoff internal structures, suchasthe skeleton,wing spars,bomb racks, thecockpit,and theengines. The Mosquito probably had a lower RCS than ametallic Lancaster or Halifax, though this amount was notmilitarilysignificant.TheMosquito’ssurvivabilitywasderivedfrom its performance rather than its RCS reduction. DougRichardson,Stealth(NewYork:OrionBooks,1989)p.42.

53.Green,p.249.

54.Green,p.251.

55.CitedinRichardson,p.96.

56.Rich,p.24,215.

57.DavidC.Jenn,Radar and Laser Cross‑Section Engineering (Washington,DC:AIAA,1995)p.6.

58.Conduct of the Persian Gulf War: Final Report to Congress(Washington,DC:DepartmentofDefense,April1992)p.154.

59. Gulf War Air Power Survey, Volume II: Operations and Effectiveness(Washington,DC:DepartmentoftheAirForce,USGPO,1993)p.79.HereafterreferredtoasGWAPS.

60.MichaelR.GordonandBernardE.Trainor,The General’s War: The Inside Story of the Conflict in the Gulf (Boston:Little,Brown,c1995)p.115.

61.GWAPSVol.II,p.123-124.

62.ThomasA.KeaneyandElliotA.Cohen,Gulf War Air Power Survey Summary Report (Washington, DC: Department oftheAirForce,1993)p.224.

63.ChristopherJ.Bowie,Untying the Bloody Scarf(Arlington,VA:IRISIndependentResearch,1998)p.15.

64. John Shaeffer, “Understanding Stealth” (Marietta, GA:MariettaScientific,Inc.,undatedpaper)p.15.


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