Stealth Design of Storm Shadow

External Configuration:

The three major design drivers in the external configuration of the Storm Shadow proved to be the payload, small size, and stealth requirements called for in the RFP. Four initial planforms were selected primarily because of their natural stealthiness--a pure flying wing, a delta wing, an X-36 derivative with canards, and an aero-diamond (see below).

Initial shapes studied by design team

Since the payload constitutes nearly 20% of the gross takeoff weight (GTOW), its center of gravity (CG) has a tremendous effect on the CG of the entire aircraft. As a result, the team concentrated on configurations that would place the CG of the bomb coincident with that of the aircraft. Thus, the release of the bomb would have little or no effect on the stability of the aircraft. This eliminated the delta wing and X-36 concepts since the wings are placed so far aft that the bomb must be located far forward to compensate. The flying wing was also eliminated because its large wingspan and length (dictated by the length of the bomb) made it impossible to fit eight in a C-5 Galaxy transport aircraft. An aero-diamond, defined as a planform on which the leading edge and opposite trailing edge are parallel, was finally selected because its shape is perfectly suited to the RFP requirements.

Aero-diamond external configuration of the Storm Shadow

A second major decision involved the choice of powerplant. It was originally hoped that one engine could be used to reduce the weight, cost, and complexity of the aircraft. However, the placement of one engine over the bomb bay would make the aircraft too thick at its center. Instead, the team chose to use two engines which straddle the bomb bay. This has the advantage of reducing the aircraft thickness, but forces an increase in wingspan to maintain the same wing area. In addition, there is an associated weight penalty from the added engine and structural weights.

Evolution of the Storm Shadow

The dimensions of the Storm Shadow shown below were finally determined by a combination of bomb bay size, engine size, aerodynamics, aero-diamond geometry, low observability, and center of gravity issues.

Storm Shadow Statistics

Dimensions:

Length 20 ft

Width 18.5 ft

Leading Edge Sweep Angle 55°

Wing Area 201 ft2

Aspect Ratio 1.7

Weights:

GTOW 5,190 lb

Empty Weight 3,249 lb

Performance:

Mission 1 Range 1,667 nm

Mission 2 Range 779 nm

Armament:

GBU-16 laser guided 1,092 lb

GBU-32 GPS/INS guided 1,035 lb

Cost:

Flyaway (1996$) $5.25 million

Life-Cycle (1996$) $7.14 million

Internal Configuration:

Internal configuration of the Storm Shadow

Internal Configuration Legend

Color: Item(s):

Yellow Structure, Langing Gear

Lt. Blue Bomb Bay

Purple Fuel Tanks

Red Engines

Dk. Gray Ducting

Salmon Control Surfaces

Green FLIR System

Orange Fly-By-Wire System

Lt. Gray Flight Computer

Dk. Blue Electronic Warfare System

Gold VHF Data Link

Dk. Red Integrated Avionics Group

An internal cut-away of the Storm Shadow is shown above. Clearly, the internal configuration is dominated by the bomb bay, two engines, and three fuel tanks. These items were placed to maintain a stable CG during most flight conditions (see Weight & Balance). The aircraft structure is composed of three wing spars and six fuselage bulkheads designed to withstand aerodynamic loading and to support items such as the engines and landing gear (see Structures).

Stealth Design:

As already mentioned, stealth was a critical driver in the overall design of the aircraft. The three types of stealth most important to the mission specifications are radar cross-section (RCS), infrared signature (IRS), and the aural (or noise) signature.

The aero-diamond was cjosen in part because its wing planform is considered to be an optimum low-observable shape. The horizontal and vertical tails were also removed in order to reduce the RCS and provide greater "natural" stealth. The two key methods of reducing RCS are to minimize the number of directions with high RCS returns and to maximize the scattering of radar waves in all other directions. This is accomplished using smooth curves rather than flat surfaces at right angles. The trailing edge has been saw-toothed such that the edges are parallel to the wing leading edges. This principal was also used in designing the bomb bay and gear doors to reduce edge diffraction, as is done on the Lockheed Martin F-117 Nighthawk stealth fighter and the Northrop B-2 Spirit stealth bomber.

Another impact of stealth issues on the aircraft configuration was engine placement and inlet design. Jet engine fan blades are highly radar reflective, so it was decided to bury the engines within the fuselage and S-duct the inlets to hide the blades from outside radar sources. The use of buried engines also reduces the IRS and aural signature of the powerplant. Due to the relatively long ducting connecting the engines to the vectoring nozzles, the exhaust has more time to cool, further reducing the IRS. The use of a high-bypass turbofan also aids in this effort. The nozzles are also effectively buried in the saw-tooths, again lowering the IRS from every angle but directly behind the aircraft.

The external skin of Storm Shadow also aids in increasing the stealthiness of the aircraft. The graphite/epoxy skin absorbs a percentage of incident radar waves and heat reducing the RCS and IRS. It is also assumed that at least part of the 500 lb allowance for classified treatments will include radar absorbant materials (RAM) which will further reduce the amount of radar reflected.

The airfoils selected for the Storm Shadow also play a role in increasing the stealthiness of the aircraft. Due to their behavior at transonic speeds (about Mach 0.6 to 1.3), no shocks should form on the airfoils since the flow remains subsonic up to approximately Mach 0.95 (less than the maximum speed of the aircraft). This not only reduces the noise signature by eliminating the possibility of sonic booms, but also helps to reduce the IRS since there is no temperature gradient across the shock.

In summation, the aero-diamond configuration of the Storm Shadow was selected because of its superb stealth characteristics and excellent suitablility to the needs presented by the RFP. The design team has carefully tailored the aircraft to optimize its aerodynamic and performance capabilities while maintaining the low observability necessary to its survival.

Wing Design:

As already discussed, the aero-diamond shape was selected because of its inherent stealth characteristics and because it would minimize the shift in center of gravity due to payload release. The basic aero-diamond shape was modified by adding saw-tooths along the trailing edge to provide locations for additional control surfaces.

Since the aero-diamond is defined as a planform on which the leading egde is parallel to the opposite trailing edge, the geometry of the planform was derived from the leading edge (LE) sweep angle, the fuselage length, and the distance between the saw-tooths. An initial LE angle of 48° was selected since it is similar to that used on the wing of the F-22 fighter. However, the wing design was later optimized to reduce drag during the Mach 0.9 ingress/egress segments. As shown below, the drag (expressed as thrust required) decreases dramatically as the sweep angle increases for the ingress case while it remains roughly constant for the cruise case. A LE angle of 55° allowed just enough internal space for structures, payload, fuel, and avionics while minimizing drag and allowing the aircraft to better fit within the C-5 transport.

Percent thrust required vs. leading edge angle

The overall length of the aircraft was dictated by the bomb bay dimensions. An airfoil shape was fitted around the bay resulting in a total length of 20 ft. Since the engine nozzles are located within the triangular cutouts, the distance between them is dictated by the diameter of the engines and bomb bay width.

Both the aerodynamic and structural design proceeded from treating the wing as being composed of an inboard wing (the fuselage) and an outboard wing, as indicated by the dashed lines in the figure below. Key characteristics of the wing are summarized in the table below.

Storm Shadow planform

Storm Shadow Wing Geometry

Inboard Wing Outboard Wing Overall Planform

Root chord: 20 ft Root chord: 13.57 ft

Tip chord: 13.57 ft Tip chord: 0 ft Aspect ratio: 1.70

Mean aero. chord: 16.99 ft Mean aero. chord: 9.05 ft Wing span: 18.5 ft

Max thickness sweep: 35.53°

Max thickness sweep: 8.13°

Leading edge sweep: 55°

Wetted area: 291.2 ft2 Wetted area: 129.3 ft2 Reference area: 201.1 ft2

Airfoil Selection:

Since the Storm Shadow is a flying wing, the proper selection of an airfoil was crucial to the success of the design. Since a flying wing typically does not have a horizontal tail to counteract pitching moments, the airfoil itself must have a low pitching moment. A second key factor in selecting an airfoil was a high critical Mach number (Mcr) to minimize shock drag. Thus, the airfoils used on both the inboard and outboard wings must have little camber to reduce pitching moment as well as a small thickness to chord ratio (t/c) and leading edge radius to insure a high Mcr. The airfoils must also be thick enough to provide a sufficient internal volume. The airfoils selected as possible candidates are listed below.

Airfoil Characteristics

Outboard Wing Leading EdgeRadius [%c]

Max ThicknessLocation [%c]

Critical MachNumber

NACA 63A008 0.473 35 0.902

NACA 64-008 0.455 38 0.900

NACA 65-008 0.434 40 0.903

NACA 66-008 0.411 45 0.908

Inboard Wing

NACA 67,1-015 1.523 50 0.848

NACA 16-015 1.100 50 0.853

The NACA 66-008 was chosen for the outboard wing because (a) its critical Mach number is less than the maximum Mach number specified by the RFP and (b) its maximum thickness is closer to the middle which better suits the structural

design. The NACA 67,1-015 was selected for the inboard wing because the bomb bay fits better within its shape.

Lift and Drag Characteristics:

Since the aero-diamond planform is relatively new, very little analytical processes for calculating the lift of such a shape have been developed. However, NASA has conducted wind tunnel tests on flat plates with planforms very similar to that of the Storm Shadow. Using these data, a more accurate estimation of the lift characteristics of the aircraft could be made. The resulting lift curves for the aircraft at various flight segments are shown below.

Lift curves for various flight segments

A standard component drag buildup was also performed for the entire aircraft yielding the results shown in the following table. Drag polars are also presented.

Drag Breakdown for Fight Segments

Segment Parasite Drag

Coefficient (CD0)

Lift Coefficient

(CL)

Induced DragCoefficient

(CDi)

Drag Coefficient

(CD)

Drag [lb]

Takeoff 0.0317 0.8760 0.0998 0.1314 784.27

Cruise 0.0079 0.1914 0.0048 0.0127 343.73

In/egress 0.0067 0.0215 0.0001 0.0067 1626.30

Landing 0.0413 0.9170 0.1093 0.1506 810.16

Drag polars for various flight segments

Engine:

The Storm Shadow uses two FJ44-2A high bypass turbofan engines (shown below) made by Williams International, a division of Rolls-Royce.

Williams FJ44-2A engine

The RFP calls for the aircraft to use an off-the-shelf commercial jet engine. Engines that could possibly be used include turbojets, turbofans, turpoprops, and engines with afterburners. Because they are not typically flown at speeds approaching Mach 0.9 and they have large radar cross-sections, turboprops were quickly eliminated. Initial sizing showed that turbojets would require too much fuel to be practical. Afterburners were eliminated because of their extreme length. This left the turbofan, which comes in both low and high bypass varieties. While the low bypass is capable of greater thrust at low altitudes, its fuel consumption was considered too great. The high bypass turbofan, however, is

much more fuel efficient. Since range is very important to the mission requirements in the RFP, the high bypass engine was finally selected.

The performance of five candidate engines are listed in the table below.

Engine Trade Study

Engine Model Thrust [lb] Takeoff SFC

[lbfuel/hr/lbthrust] Weight [lb] Length [in]

FJ44-1A 1,900 0.47 448 40.2

FJ44-2A 2,300 0.50 520 47.2

PW530A 2,900 0.47 616 60.3

JT15D-5D 3,045 0.56 627 61.0

PW545A 3,804 0.50 805 68.6

Because of its high SFC (a measure of fuel consumption), the JT15D-5D was quickly eliminated. The FJ44-1A was found to be incapable of achieving the performance requirements called for in the RFP, and was also eliminated. The PW545A was too heavy, and the PW530A too long. The FJ-44A was selected because it offers the best compromise between low fuel consumption, small size, and good thrust to weight ratio. The FJ44-2A has also proven itself in many commerical aircraft including the Cessna Citation Excel and the Raytheon Primary One business jet. Military aircraft such as the Dark Star also use this engine.

Engine/Inlet Location:

Since the engines are large, concentrated masses, their location was largely dictated by center of gravity and stability issues. The inlet is an S-ducted pitot inlet. S-ducting was used primarily for stealth as it allows the radar reflective fan blades to be hidden. As a result, 90% of the fan blades are hidden from a head on view. The layout of the propulsion system is indicated below.

Engine, inlet, and fuel tank locations

Nozzle Configuration:

The aircraft uses 2-D thrust vectoring nozzles to increase maneuverability and assist in pitch control. The dimensions of the nozzle louver arms are shown below.

Nozzle configuration

Engine Performance:

Since very little actual performance data for the FJ44-2A engine was provided by the manufacturer, similar engines for which such data was available were used to create a model. Using this model and analytical methods, the following engine performance predictions were made.

Projected installed full throttle thrust vs. Mach number at various altitudes

Projected installed max power SFC vs. Mach number at various altitudes

Projected installed cruise SFC vs. altitude at various Mach numbers

Fuel System:

The FJ44-2A can operate using several types of fuel: Jet A, JP4 through JP8 and (for 50 hours in emergency situations) 100LL. As shown in the internal configuration, fuel is carried in the wings and above the bomb bay. The tanks are composed of self-sealing fuel bags to minimize leaking and fire from combat damage. A fourth drop tank is carried within the bomb bay during the ferry mission. A fuel dump system is included for emergency landings with exit points located at the wing tips.

Static Longitudinal Stability:

Two key factors which determine the aerodynamic center of a wing are the geometry of the planform and the aerodynamic center of the airfoil. Since the Storm Shadow has been designed without traditional tail control surfaces, the ability to control the aerodynamic center is limited to these fundamamental characteristics of wing design.

The selection of a proper airfoil is discussed here. As also discussed in the aerodynamics section, the geometry of the planform was largely determined by the sweep angle and distance between engines. After careful consideration of the aerodynamic, configurational, and stability effects of these parameters, a sweep angle of 55° and an engine spacing of 54 in were selected. These values and the airfoil aerodynamic center locate the aerodynamic center of the entire aircraft 8.3 ft behind the aircraft nose.

To be stable, the center of gravity (CG) must be at or forward of this location at all times. Though not easy to accomplish, the Storm Shadow is stable in all configurations except takeoff. Because of this, a fly-by-wire flight control system with a computer controlled feedback loop has been implemented.

Control Surfaces:

Pitch, or longitudinal, control is typically provided by elevators on a horizontal control surface. Since the Storm Shadow lacks a horizontal tail, both trailing edge flaps and thrust vectoring nozzles are provided to achieve pitch control. The flaps are sized as 20% of the outboard wing chord yielding a flap effectiveness of -0.00505 change in lift coefficient (CL) per degree of deflection.

Using the flap effectiveness and the drag polars, the flap deflections needed to maintain steady flight at various CL values were claculated. These trim curves, shown below, can be compared to the same deflections needed if thrust vectoring were used to trim the aircraft.

Flap deflection to trim

Thrust vector angle to trim

Since the thrust vectoring is more effective at high CL values, the nozzles would likely be used during takeoff and landing when the flaps would be needed to increase lift.

Yaw control in needed to turn the aircraft, and to maintain straight flight in a crosswind or when one engine is inoperative (OEI). This control is provided by a rudder in a traditional vertical tail assembly. Since the Storm Shadow does not have a vertical tail, a different method had to be found. Inspired by the B-2 stealth bomber, a drag rudder arrangement was selected. Further strengthening this decision are a series of NASA wind tunnel experiments on an aero-diamond

wing planform showing that drag rudders are more effective than a typical fin and rudder combination. The rudders may also be used for braking during landing.

Roll control is provided by the outboard flaps which also act as ailerons. Since these flaps have the longest moment arm, they are most effective in producing a roll.

Leading edge flaps are also provided to be used in conjuction with the trailing edge flaps to produce a cambered effect. By adjusting both sets of flaps, the aircraft can be trimmed at any CL while minimizing drag. The leading edge flaps may also be used to alleviate leading edge separation at high angles of attack.

Control surface configuration

Structural Design

Maneuver Envelope:

The maximum loadings anticipated during a typical mission of the Storm Shadow are represented in the velocity-load (V-n) diagram shown below.

Velocity-load diagram

While this maneuver envelope is similar to that of a small military attack aircraft, the stringent requirements called for in the RFP dictate larger load limits than might otherwise be expected. The most important value shown on the V-n diagram is the operational load limit of +8g chosen to satisfy performance requirements. An additional 25% safety factor has been added corresponding to a +10g structural limit, beyond which the aircraft will suffer damage and failure.

Wing Loading:

The forces acting on the aircraft include structural weight, fuel weight, and point loads (e.g. bomb, engine, and landing gear).

Loads acting along half of wing

Each of these loads and the combined load during 1g flight along half of the wingspan are illustrated below.

Load distribution vs. half-span location

From this data, the maximum shear, bending moment, and torsion acting on the wing were computed and used to design the aircraft structure.

Sturctural Design:

The wing spars counteract the majority of the load acting on the wing. The spar design was optimized to withstand the maximum load on the wing while minimizing the overall structural weight. The optimum arrangement was found to

be three spars: one located at 45% chord, or the point of maximum thickness, since this location best counteracts the stress on the spar, and others at 15% and 60% chord to provide attachments for control surfaces. Ribs are also used to join the spars and reduce wing twist.

The fuselage uses a series of ring-framed bulkheads to maintain the fuselage shape and to support point loads like the engines and landing gear. The three center bulkheads serve as the wing carry-through structure through which the loads on the wings are transmitted. A series of four longerons run the length of the aircraft adding longitudinal stiffness.

The aircraft skin was designed to resist the torsion which tends to twist the aircraft. The structural arrangement of the aircraft is illustrated below.

Storm Shadow structural arrangement

Material Selection:

The wing spars are composed of a high strength unidirectional graphite/epoxy composite material chosen for its high strength and low weight. The fuselage bulkheads are made of a high strength aluminum alloy. This arrangement was chosen through a trade study to determine the optimum balance between overall structural weight and cost. Because of its stealth and torsional strength characteristics, a high modulus graphite/epoxy was also selected for the aircraft

skin. A further use of advanced composites is the placement of 1/2-inch Kevlar armor around the engines. This was done to improve survivability since the aircraft spends much of its time at low levels where critical systems must be protected from battle damage. The usage of materials on the aircraft are summarized in the following table and weight distribution graph.

Material Selection

Material Usage Advantages Disadvantages

High strength unidirectional graphite/epoxy

Spar caps High strength, low weight

High cost, low impact resistance, difficult to manufacture

High modulus ±45° graphite/epoxy

Skin (w/foam core), Shear web, Wing ribs

High strength, low weight, low surface roughness, stealth characteristics

High cost, low impact resistance, difficult to manufacture

Aluminum 7075-T6 Bulkheads, Longerons

Low cost, ease of manufacture, good sturctural efficiency

Low strength, not weldable

Stainless steel (AM-350)

Landing gear Relatively low cost, high strength, corrosion resistance

High weight

Nickel (Hastelloy B)

Nozzles and ducting

Temperature resistance

Low structural resistance

Kevlar Internal armor High strength, low weight, high impact resistance

High cost, difficult to manufacture

Material breakdown by weight

Landing Gear:

The aircraft uses a tricycle landing gear arrangement. As shown below, each gear strut is attached to a bulkhead while the drag strut (which provides extra rigidity) is attached to the gear boxes (not shown for clarity) containing the gear. The nose gear retracts backward and rotates to lie parallel to the aircraft leading edge. The main gear retract forward, and as they do so, the strut uses a spiral retraction mechanism to rotate the wheel flush with the aircraft skin. The gear also fold just below the oleo shock absorber to fit between the bulkheads. As each gear retracts, the telescoping drag brace shortens while its end slides down the strut allowing the brace to stow alongside. Though the retraction mechanisms are complex, they are required by the limited space available within the aircraft.

Landing gear geometry

Weight and BalancesSizing:

The aero-diamond shape was selected because of its superior aerodynamic, stealth, geometry, and internal volume characteristics. After performing an initial statistically-based analysis, a GTOW of 8,000 lb was calculated. However, this estimate was based on data for manned aircraft. Since much of the equipment needed for a human pilot can be eliminated in the Storm Shadow, the design team hoped to be able to reduce the GTOW to 5,000 lb.

Once actual weights for various components were found or better calculated using weight estimation equations suitably modified for an unmanned aircraft, the GTOW did indeed come very close to this mark. Very precise data were available for items such as the payload, engines, and several avionics systems. Very good approximations could be made for structural materials and fuel while the weight of some auxiliary systems had to be estimated as accurately as possible. The final results are summarized in the following table and graph.

Major Weight Groups

Item Weight [lb] Location of CG

[ft back from nose]

Bomb 1,092.0 8.21

Wing 100.3 9.80

Fuselage 384.9 8.40

Wing Fuel 527.5 10.50

Fuselage Fuel 322.5 7.50

Avionics 285.1 3.00

Engines (2) 1,040.0 10.0

Classified Materials 500.0 11.0

Extra Fuel (ferry) 484.0 6.5

Empty Weight 3,248.8

Fuel Weight 850.0

Gross Takeoff Weight 5,190.8

Weight breakdown

Center of Gravity Location:

To be controllable, the CG of an aircraft must remain within an "envelope" containing the aerodynamic center. The controllable envelope of the Storm Shadow is shown below. Note that the CG of the aircraft remains within this envelope during all flight configurations.

CG envelope diagram

As shown above, the movement of the CG along the longitudinal axis is limited to about 3.5 inches. This figure also includes the effect of fuel sloshing during the climb and descent phases of missions 1 and 2. Furthermore, the figure illustrates that the Storm Shadow is controllable and stable throughout its flight with very little CG movement.

Avionics

Avionics:

Since the Storm Shadow is an unmanned aircraft, it will rely heavily on its onboard avionics systems. The most important advance in technology that makes this type of aircraft possible is the Global Positioning System (GPS). The

aircraft uses differential GPS for its navigation to ensure reliable autonomous control. Because the aircraft is designed to operate independently of human control for the majority of its mission, a flight computer is also provided. Able to access the onboard integrated avionics system, center of gravity control computer, and fly-by-wire control system, the computer is able to maintain control of the aircraft at all times. The primary auxiliary systems carried aboard the aircraft are summarized below.

Auxiliary Systems Summary

Name Manufacturer Weight

[lb] Dimensions [in] Cost

Multi-ApplicationControl Computer

Hamilton StandardDivision of UTC

17.11 10.15 x 7.63 x 10

unknown

Modular IntegratedAvionics Group

Lear Astronautics 7.0 5 x 5.5 x 5.6 $100,000

VHF Data Link Harris Aerospace 5.0 3 x 6 x 8 unknown

Anti-jamming adaptiveGPS antenna

Harris Aerospace 1.0 6 x 0.5 unknown

Ultra 6000 FLIR Flir Systems Inc. 42.0 11 x 11 x 15 $13,000

Fly-by-wire system AlliedSignalElectronic Systems

44.1 18 x 10 x 27 unknown

Center of GravityControl Computer

Sextant Avionique 8.2 2 MCU unknown

AN/APR-50 defensivemanagement suite

Lockheed Martin 40.0 unknown unknown

The breakdown of avionics as part of the overall auxiliary systems weight is as follows:

Auxiliary systems weight breakdown

Product Descriptions:

The Multi-Application Control Computer (MACC) can be monitored and controlled by a remote ground station and is capable of processing the inputs from 50,000 sensor sets. The MACC is currently used in aircraft for flight control, vehicle management system control, and actuator/subsystem control.

The Modular Integrated Avionics Group/Navigation Sensor Unit (MIAG) is a vehicle management system with integrated local air data specifically designed for use in UAV's. The MIAG utilizes a DGPS receiver for pre-programmed aircraft navigation as well as general aircraft position data. In addition, several air data pressure transducers supply the flight computer with necessary airspeeds and altitudes. The unit also contains an engine command and control system as well as a payload management system for operating the bomb bay and bomb rack. The MIAG has a built in IFF (identification--friend or foe) system and a fiber optic inertial measurement unit (IMU) to assist in attitude and heading references.

The Harris VHF Data Link and adaptive DGPS antenna were designed for military use in areas filled with hostile electronic environments. The antenna is the primary system used to feed date to the MIAG.

The Ultra 6000 airborne imager provides final targeting, imaging, and man-in-loop flight control. The system uses a high resolution CCD camera with a 15:1 zoom and advanced focal plane array detector technology to deliver high resolution infrared images. The system is capable of detecting thermal differences of less than 0.03 degrees C and can penetrate darkness, fog, and foliage to identify people and targets. The entire system is self-cooled with a Sterling closed cycle cooler. To designate targets for the GBU-16 bomb, a laser designator is attached to the FLIR so that targets can be acquired independently. The FLIR is located in the nose of the aircraft giving it the ability to see below and in front of the aircraft.

The avionics suite operates the control surfaces and thrust vectoring via an analog fly-by-wire system. The FBW used on the aircraft is the same as that used on the pre-block 40 F-16 Fighting Falcon fighter.

To remain stable in flight, fuel must be drawn equally from each of the tanks aboard the aircraft. The Center of Gravity Computer is included for this purpose since it assists the FBW in maintaining smooth, stable flight.

The AN/APR-50 electronic warfare system is currently used on the B-2 Spirit . The system is capable of covering the lower frequencies and up to Band 4 from 500 MHz to 1 GHz. Otherwise, very little information is available on this highly classified system.

During payload release, a human pilot will take control of the aircraft from a ground station. Most UAV programs currently employ ground stations to input pre-programmed navigation controls and to control the aircraft when necessary. The ground station for the Storm Shadow consists of VHF transmitters and receivers as well as hardwire connectivity with the TROJAN SPIRIT II satellite communications terminal for over-the-horizon communications. The station is manned by two: a pilot with access to all necessary flight information and a payload officer responsible for releasing the weapon. A "backpack" version of the station, operated by a pilot/payload officer in a forward deployed situation, is also possible.

As this site has illustrated, the Storm Shadow is a sophisticated yet cost-effective solution to the requirements specified in the AIAA Request for Proposal. Perhaps the best way to illustrate the strengths of this design is to compare it to several current aircraft that perform similar missions.

Storm Shadow vs. the Competiton

Specification F-16 A-6 F-22 Joint Strike

Fighter F-117

Storm Shadow

Mission Tactical Fighter

Ground Attack

Air Superiority

Tactical Fighter

Ground Attack

Ground Attack

Takeoff Weight [lb]

37,500 58,000 60,000 ~50,000 52,500 5,190

Payload [lb] 17,000 18,000 8,000 ~15,000 5,000 1,000

Combat Radius [nm]

270 470 1,000 ~700 570 800

Length [ft] 49.33 54.75 62.08 ~50.00 65.92 20.00

Wingspan [ft] 31.00 53.00 44.50 ~40.00 43.25 18.50

Cost (millions $)

20+ 22 100 ~35 45 5.25

The above comparisons provide some surprising results favoring the Storm Shadow design. This is especially true when compared to the aircraft it is most likely intended to replace, the F-117 stealth fighter. As indicated, the Storm Shadow can carry a payload similar to that of the F-22 or F-117, yet possesses a range greater than most of the other aircraft listed (although all are capable of refueling in flight except the Storm Shadow). The Storm Shadow is also much smaller than any of the aircraft shown, and it is also far less expensive. These comparisons not only prove the merit of the Uninhabited Combat Aerial Vehicle (UCAV), but exemplify the superb capabilites of the Storm Shadow. When faced with Congressional threats to slash the number of new F-22s or Joint Strike Fighters that can be purchased, the military may turn to the UCAV to perform critical missions in defense of US interests. Able to perform many of the same missions as manned aircraft at a fraction of the cost, an aircraft like the Storm Shadow may well become the premier attack aircraft of the future.