federal aviation administration transport airplane and engine safety requirements a general overview...

FEDERAL AVIATION ADMINISTRATION

TRANSPORT AIRPLANE AND ENGINE SAFETY REQUIREMENTS

A GENERAL OVERVIEW

Certification Process Study Team Meeting #6Museum of Flight, Seattle WAJune 26-27, 2001

TABLE OF CONTENTSTABLE OF CONTENTS

• Introductory Remarks (D. Cheney)• Flight: Airplane Performance, Stability and Control,

Related Support (T. Archer/J. Neff)• Structures: Loads, Design and Construction (H.

Offerman)• Equipment: Mechanical (R. Jones)• Equipment: General, Electrical, Avionics

(S. Boyd)• Propulsion: Engine/APU (M. Fulmer)• Propulsion: Engine Installation (K. Rask)• Cabin Safety (F. Tiangsing)• Human Factors (S. Boyd)

CERTIFICATION FLIGHT TESTCERTIFICATION FLIGHT TEST

Tom Archer - FAA Flight Test Pilot John Neff - FAA Flight Test Engineer

Flight Test Branch

Seattle Aircraft Certification Office

CERTIFICATIONCERTIFICATION FLIGHT TESTFLIGHT TEST

• Overview– Flying Qualities– Systems and Equipment – Aero. Performance– Airplane Flight Manual

CDL– Operations Manual / MMEL

CERTIFICATION FLIGHT TESTCERTIFICATION FLIGHT TEST

• Flying Qualities (FAR 25, Subpart B)

• Aircraft Systems (FAR 25, Subparts D, E, & F)– Aircraft Systems– Installed Equipment

• Performance (FAR 25, Subpart B)

• Airplane Flight Manual (FAR 25 Subpart G)

FLIGHT TEST - GOALFLIGHT TEST - GOAL

• Ensure aircraft meets minimum standards– Fully operational aircraft or– with any foreseeable failures (more probable

than 1x10E-9) – with a pilot of average skills– throughout the operational envelope:

Speed Altitude Gross Weight / Center of Gravity Temperature Limit head/tail/cross winds

FLYING QUALITIES (FQ)FLYING QUALITIES (FQ)

• General Requirements-– The airplane must:

Be safely controllable and maneuverable Not require exceptional piloting skill,

alertness or strength Be capable of continued safe flight and

landing following any single failure or combination of failures not shown to be extremely improbable.

– The flying qualities requirements must be demonstrated throughout the flight envelope

FLYING QUALITIES (FQ) FLYING QUALITIES (FQ) (cont’d)(cont’d)

• Stability– Static– Dynamic

• Controllability• Maneuverability• Stall Characteristics• High Speed Characteristics• Degraded Modes

FLIGHT ENVELOPEFLIGHT ENVELOPE

• The airplane must exhibit acceptable flying qualities at the most critical loading within the ranges of speed and altitude for which certification is requested.– The airline pilot is provided with a safe operational

flight envelope (bounded by certificated limits) that has been thoroughly explored during flight testing.

– The airplane is test flown outside of it’s operational envelope to account for inadvertent excursions beyond the certificated limits.

C.G./GROSS WEIGHT ENVELOPEC.G./GROSS WEIGHT ENVELOPE

Gro

ss W

eigh

t (P

oun

ds)

Center of Gravity (%MAC)

FLIGHT ENVELOPEFLIGHT ENVELOPEP

ress

ure

Alt

itu

de

(Fee

t)

Airspeed (KCAS)

V-N DIAGRAMV-N DIAGRAM

SPECIFIC FQ FLIGHT TESTSSPECIFIC FQ FLIGHT TESTS

• General (25.101-.143)• Maneuvering stability

(25.143, .251, .255)• Longitudinal control

(25.145)• Directional and lateral

control (25.147)

• Minimum control speed (25.149)

• Trim (25.161)• Static longitudinal

stability (25.173-.175)• Static lateral-directional

stability (25.177)

SPECIFIC FQ FLIGHT TESTS SPECIFIC FQ FLIGHT TESTS (Con’t)(Con’t)

• Dynamic stability (25.181)

• Stall characteristics (25.203)

• Ground handling (25.231-.235)

• Cross wind (25.237)

• Vibration and buffeting (25.251)

• High-speed characteristics (25.253)

• Out-of-trim characteristics (25.255)

TEST CONDITIONSTEST CONDITIONS

TEST LOADING(wt/cg)

DATA

General Full range Qual, forces

Man stab “ Fs/g

Long control Heavy/fwd, aft Qual, forces

Lat-dir control Heavy/fwd, aft “

TEST CONDITIONS TEST CONDITIONS (Con’t)(Con’t)

TEST LOADING DATA

Min cont spd Light/aft Hdg, grd track

Trim Full range Control forces

Stat long stab Light/aft Fe/V

Stat lat/dir stab Light/aft Fa/, Fr/


TEST LOADING DATA

Dyn stability Light/aft Oscillations

Grd handling Full range Qualitative

Stall char Light/aft , response

Vib/buffet Heavy/aft Fs/g, Vc, Mach


TEST LOADING DATA

High spd char Full range Fs/g, Vc, Mach

Out-of-trimcharacteristics

Full range Fs/g, Vc, Mach

ADDITIONAL APPROVALSADDITIONAL APPROVALS

• Human Factors- continuous evaluations conducted concurrently with other tests

• Operating Limitations (FAR 25, Subpart G)- sufficient to define the envelope demonstrated during flight tests

• Airplane Flight Manual (FAR 25, Subpart G)- information validated during flight testing

SYSTEMSSYSTEMS

• Systems and equipment evaluated by Flight Test– All Systems– Virtually every piece of equipment on the A/C

Three categories of equipment> Equip. required by FAR Part 25> Equip. NOT required by FAR 25, but IS by FAR 91,

121, 125, or 135, > Equip. not required by any FAR

SYSTEMSSYSTEMS

• ALL equip. MUST meet the following rules– Perform it’s intended function/function

properly– Not provide any misleading information to

crew– Not interfere with any other equipment– Specifically applicable rules (if any)– No failure condition may preclude continued

safe flight and landing

AIRCRAFT SYSTEMSAIRCRAFT SYSTEMS

• Flight Controls• Landing Gear • Powerplant • Fuel • Auto Flight

– Flight Director– Auto Pilot – Auto Throttle– HUD

• Hydraulics

• Electrical• Pressurization/Environ.• Fire Protection• Flight Deck

– Controls– Displays

• Lights• Safety• Comm/Nav• De-ice/Anti-ice

FLIGHT TEST - FIRE/SMOKE FLIGHT TEST - FIRE/SMOKE

WATER IMPINGEMENTWATER IMPINGEMENT

COLD / HOT ENVIRONMENTCOLD / HOT ENVIRONMENT

WINDOWS / DOORSWINDOWS / DOORS

INSTALLED EQUIPMENTINSTALLED EQUIPMENT

• Operational Requirement– TCAS – GPWS/EGPWS – RWS/PWS– CVR– FDR– HF– 3rd Comm/Nav– Standby Instruments

• Optional– ACARS– GPS– IFE– Telephones– SAT Comm– Lavatories– Prayer Rooms

PERFORMANCEPERFORMANCE

• Phase of Flight– Takeoff (FAR 25.105 - .107)

Accelerate - Go Accelerate - Stop (FAR 25.109)

– Climb (FAR 25.113 - .117, .121) First / Second / Third / Final segment

– En Route (FAR 25.123)– Descent– Approach

Approach climb (FAR 25.121)– Landing (FAR 25.125)

Landing climb (FAR 25.119)

T.O. PERFORMANCET.O. PERFORMANCE

• Takeoff Speed Schedule Development (FAR 25.107)

• Takeoff Field Length Requirements (FAR 25.113)

HIGH ALTITUDE TAKEOFF PERF.HIGH ALTITUDE TAKEOFF PERF.

LaPaz, Bolivia, field elevation 13,100 ft. MSLLaPaz, Bolivia, field elevation 13,100 ft. MSL

TAKEOFF SPEEDSTAKEOFF SPEEDS

• Definitions for speed schedule development– V1 Takeoff “decision speed”

Min. speed, following critical engine failure, from which T.O. can continue and achieve 35’ within T.O. distance

Max speed to initiate the first action in an abort and stop within accel-stop distance

less than V1MBE

Brake Release Vef Vr >V2VlofV1

35 feetVmcg Vmca

Vmu

Max. tire speed

Vmbe(15’ if wet)(15’ if wet)

TAKEOFF SPEEDS TAKEOFF SPEEDS (cont’d)(cont’d)

• Definitions for speed schedule development– Vr Rotation speed

Equal to, or greater than, V1, and 1.05 Vmca result in a minimum Vlof of 1.05 OEI Vmu & 1.1 AEO Vmu Allow reaching V2min by 35’, OEI 5 knot abuse (OEI) will not significantly extend the

takeoff distance

Brake Release Vef Vr

>V2

VlofV135 feet

Vmca Vmu

TAKEOFF SPEEDS TAKEOFF SPEEDS (cont’d)(cont’d)

• Definitions for speed schedule development– V2 Takeoff Safety Speed

Meet minimum EO climb gradient Greater than V2min

– V2min 1.1Vmca 1.13Vs

Brake Release Vr

V2

V135 feet

VmcaVs

ADDITIONAL SAFETY MARGINSADDITIONAL SAFETY MARGINS

• T.O. Tests @ each flap setting– Light / mid / heavy weights– All engine / one engine inoperative– Several T/W at each flap setting– Fuel cut conditions– Overspeed– Abuses

Rapid rotations (rate) Over rotations 5 knot Vr abuse Mis-trim

• Over 60 Takeoffs

FAR TAKEOFF FIELD LENGTHFAR TAKEOFF FIELD LENGTH

“AFM” Takeoff Distance Required

Vr Vlof

35 feet

Demonstrated All Engine Distance

Takeoff Distance = 1.15 X All Eng. Dist. To 35 feet

>V2

All engine, “full up” airplaneAll engine, “full up” airplane

FAR TAKEOFF FIELD LENGTH FAR TAKEOFF FIELD LENGTH (cont’d)(cont’d)

Critical Engine Fails at Vef“Balanced” field length

“GO”

V2

VlofVr35 feet

Vef

V1

“RTO”

Throttles / max. brakes, speed brakesAFM expansion, incl. 2 sec. At V1

Dry Runway - NO credit for thrust reversersWet Runway - Credit given for thrust reversers

FAR TAKEOFF FIELD LENGTH FAR TAKEOFF FIELD LENGTH (cont’d)(cont’d)

“RTO”

VlofVr35 feet

Vef

V1

“GO”

Throttles / max. brakes, speed brakes

Vr Vlof

35 feet

Takeoff Distance = 1.15 X All Eng. Dist.

Vef

Dispatch Runway Requirement, the longest distance of:

REFUSED TAKEOFF - STOPPINGREFUSED TAKEOFF - STOPPING

• 100% MBE RTO– Demonstrated performance with:

90% (min.) worn brakes (accident investigation)> FAR 25.109

Pre-heated, 3 mile taxi w/ three stops full stop - 5 minutes

ANTI SKID - INOPERATIVEANTI SKID - INOPERATIVE

CLIMB PERFORMANCE CLIMB PERFORMANCE

• Takeoff Path Segments (FAR 25.115)– 1st = Liftoff to gear up – 2nd = gear up to 400 ft.– 3rd = 400 ft. to 1500 ft. (accel/cleanup)– Enroute = Greater of: 1500 ft. or clean, MCT & at

final climb speed

• Min. climb requirements based on: – Weight– Altitude– Temperature– Most unfavorable CG

TAKEOFF PATHTAKEOFF PATH

• Minimum Climb Gradient (FAR 25.117)– Based on total number of engines– Takeoff segment – All engine / OEI, and two EI for quads

• Operational Requirements (FAR 121, Subpart I)

ENROUTE PERFORMANCEENROUTE PERFORMANCE

• Enroute (FAR 25.123) – Following data must be determined and

published Climb performance, all engine and OEI Drift down Procedures associated with the above

APPROACH PERFORMANCEAPPROACH PERFORMANCE

• Approach Climb (FAR 25.121)– Min. climb gradient, based on:

Approach configuration Total number of engines Critical engine inoperative Max. landing weight

FAR LANDING FIELD LENGTHFAR LANDING FIELD LENGTH

Vref “landing threshold speed” Vref min = 1.23Vsr

FAR 121 “FACTORED” Landing Distance (121.195)

Touch down

FAR 121 Landing Distance = demonstrated 0.6

50 feet

transition deceleration in full braking config.

Full stop

FAR 25 Landing Field Length

landing flare

Vref

FAR 25.125FAR 25.125

AIRPLANE FLIGHT MANUALAIRPLANE FLIGHT MANUAL

• AFM (FAR 25.1581)– Four sections

Limitations Normal procedures Non-normal procedures Performance

– Appendices Configuration Deviation List Derated thrust operations Engine intermix Alternate Weight

AFM / CDLAFM / CDL

• CDL contains additional limitations required for operations with missing secondary parts– PIC notified and provided a list of all parts– Each limitation listed by placard in flight deck– Logbook entry– Cumulative performance decrements via

weight penalty

OPERATIONS MANUAL / MMELOPERATIONS MANUAL / MMEL

• Flight Crew Operations Manual (FCOM) (FAR 121.141)– Permits OM in lieu of the FAR Part 25 AFM– Must contain Limitations from AFM– Perf. data / procedures can be modified from AFM– NOT FAA Approved, “Accepted” by POI

• Master Minimum Equipment List (FAR 121.627) – Permits operation of the aircraft in a “non-standard”

configuration– owned by AEG

FLIGHT TEST - CONCLUSIONFLIGHT TEST - CONCLUSION

• Huge improvements in recent years– Analytical Methods– Dynamometer Testing– Simulation

• Only Flight Test– Total Integrated Package– Real World Environment– Human Factors

• Questions?

PART 25 STRUCTURES RULESPART 25 STRUCTURES RULES

Hank OffermanAirframe Branch

Transport Airplane Directorate

CERTIFICATION OF STRUCTURECERTIFICATION OF STRUCTURE

• CFR 14, Part 25 - Airworthiness Standards– Subpart C, Structure

Loads, design conditions, proof of structure– Subpart D - Design & Construction (Structure)

Material & process specifications, special factors, design criteria, special considerations

– Subpart G - Operating Limitations & Information Airspeed, weight, center of gravity

> Limits can not exceed values used for design in Subpart C

Instructions for Continued Airworthiness> Inspection requirements

» Locations, intervals, methods, acceptance criteria

DESIGN LOADSDESIGN LOADS

• Flight Maneuver & Gust (25.331 - 25.351)• Ground Loads (25.471 - 25.519)

– Landing loads– Ground handling loads

Taxi & ground maneuver– Towing loads– Jacking & tie-down loads

• Control Surface & System Lds (25.391 - 25.459)• Emergency Landing Conditions (25.561 - 25.563)• Supplementary Conditions (25.361 - 25.373)• Fatigue Evaluation (25.571)• Lightning Protection (25.581)

MANEUVER LOADSMANEUVER LOADS

• Response to Control Input or Command– Pilot– Automatic flight control system

• Symmetric– Balanced maneuvers

Steady state> Zero pitching acceleration

– Checked maneuvers Rational pitch vs. time profile

– Unchecked maneuvers Maximum control deflection


• Asymmetric– Rolling conditions

Sudden deflection of controls Steady state roll maximum control

deflection– Yaw maneuver conditions

Sudden deflection of controls Overswing yaw maximum control deflection Steady sideslip maximum control deflection Sudden return to neutral


• Airplane Flight Configuration– Cruise configuration

With and without in-flight lift and drag devices– Takeoff, approach & landing

• Airplane Weight Configuration– All critical weight & center of gravity

combinations on or within the C.G. envelope– All critical fuel load combinations

• Airplane Speed & Load Factor– All critical speed & load factor combinations on

or within the maneuver envelope


• Load Factor - “n”– The inertial or acceleration forces acting on a

body (f) is the load factor times the weight (w) of the body

f = n x w

• Sign Convention - Airplane Axis System– Positive - push you into your seat– Negative - lift you out of your seat

DESIGN V-N ENVELOPESDESIGN V-N ENVELOPES

• Defined by Experience– Based upon extensive flight measurement

60 year history - on-going programs– Values selected such that probability of

exceedance is small– Relationships defined to ensure safe operation

in usage environment– Does not constrain airplane usage in the

operational environment– Enables minimum weight design


• Maneuver Design Load Factors– V-n diagram

GUST LOADSGUST LOADS

• Gust is an Atmospheric Disturbance– Direction - change in angle of attack– Velocity - change in local airspeed

• Result of Gust is Change in Aerodynamic Force Acting on Airplane– Acceleration - change in load factor

• Two Structural Load Components– Rigid body response– Dynamic response due to airplane flexibility and

gust velocity profile

GUST LOADSGUST LOADS

• Present Evaluation Requirements– Discrete gust

Excites rigid body response> Provides a dynamic component

Single encounter - defined gust profile Includes airplane dynamic response

– Continuous gust Atmosphere model - power spectral density

> Atmospheric energy vs. frequency Excites dynamic components

> Provides a rigid body component Envelope design - high loads Mission analysis - fatigue spectrum

GUST ENVELOPEGUST ENVELOPE

• Gust Design Load Factors– V-n diagram

GROUND LOADSGROUND LOADS

• Ground Loads are Computed using Weights and Centers of Gravity Which Result in Maximum Design Loads in Each Landing Gear Element – Forward, aft, vertical and lateral centers of

gravity locations must be considered


• Landing Loads– Applied to landing gear and airplane

• Landing Parameters– Descent velocity

Maximum landing weight - 10 feet per second Maximum takeoff weight - 6 feet per second

– Landing load factors Function of landing gear energy absorption

characteristics Must be validated by tests


• Landing Conditions– Level landing (nose landing gear arrangement)

Main gear in contact, nose gear clear All three gear in contact

– Tail down landing– One-gear landing– Drift landing– Rebound landing


• Ground Handling Loads– Taxi, takeoff and landing roll

Roughest ground reasonably expected– Braked roll

Main gear in contact, nose gear clear All three gear in contact

– Turning Side load due to centrifugal load factor

– Nose wheel yaw & steering Side load on nose gear

– Pivoting Landing gear torque

– Reversed braking


• Towing Loads– Defines loads to be applied to the towing

fittings– 30% of the towed weight for airplanes

weighing less than 30,000 pounds– 15% of the towed weight for airplanes

weighing more than 100,000 pounds– Linearly varying between 30,000 and 100,000

pounds


• Jacking & Tie-Down Loads– Airplanes must have jacking provisions– Loads computed at maximum ramp weight– Airplane

Loads resulting from a vertical load factor of 1.33 plus a horizontal load factor of 0.33 in any direction

– Fittings & local structure Loads resulting from a vertical load factor of

2.00 plus a horizontal load factor of 0.33 in any direction

– Tie-down fittings and local structure (IF provided) Loads resulting from a 65 knot horizontal

wind in any direction

CONTROL SURFACE & SYSTEM CONTROL SURFACE & SYSTEM LOADSLOADS

• Control Surfaces Must be Designed for Loads Resulting From– Flight conditions

Loads need not exceed those resulting from the application of maximum pilot effort loads

– Ground gust conditions– Loads parallel to hinge line

Load factor of 12 for horizontal surfaces and 24 for vertical surfaces

• Must Consider– Pilot effort effects– Trim tab effects– Unsymmetrical loading

CONTROL SURFACE & SYSTEM CONTROL SURFACE & SYSTEM LOADSLOADS

• Control System Must be Designed for Maximum Pilot Effort Loads– Aileron, wheel

80 x wheel diameter pound-inches– Elevator, wheel

300 pounds– Rudder

300 pounds• Criteria for Dual Control Systems

– Pilots acting together– Pilots acting in opposition

EMERGENCY LANDING EMERGENCY LANDING CONDITIONSCONDITIONS

• Protection of Occupants• Protection of Systems Which Could Cause

Fire or Explosion• Design Load Factors

– Up - 3.0– Forward - 9.0– Sideward - 3.0 for airframe, 4.0 for seats– Downward - 6.0– Aft - 1.5

• Dynamic Conditions for Seats– “16 g seats”

SUPPLEMENTARY CONDITIONSSUPPLEMENTARY CONDITIONS

• Engine Torque– Operating torque– Engine acceleration– Sudden engine stoppage

• Side Loads on Engine Mounts• Pressurized Compartments• Unsymmetrical Loads Due to Engine

Failure• Gyroscopic Loads• Speed Control Devices

DAMAGE TOLERANCE & FATIGUE DAMAGE TOLERANCE & FATIGUE EVALUATION OF STRUCTUREEVALUATION OF STRUCTURE

• “An evaluation of the strength, detail design, and fabrication must show that catastrophic failure due to fatigue, corrosion, manufacturing defects, or accidental damage, will be avoided throughout the operational life of the airplane” FAR 25.571(a)


• Damage Tolerance Evaluation– Address catastrophic failures due to fatigue,

corrosion & accidental damage Crack growth analysis and/or tests Residual strength evaluation Inspection & maintenance procedures

– Applied to single load path structure– Applied to multiple load path and crack arrest

“fail safe” structure where it cannot be demonstrated that failure will be detected during normal maintenance


• Damage Tolerance Evaluation (Cont’d)– Wide spread fatigue damage will not occur

during the design service life of the airplane Supported by full scale fatigue test evidence

• Damage Tolerance (Discrete Source)– Bird impact– Uncontained fan blade impact– Uncontained engine failure– Uncontained high energy rotating machinery

failure


• Fatigue (Safe Life) Evaluation– May be used when the application of the damage

tolerance requirements is impractical• Sonic Fatigue Strength

– Sonic fatigue cracks are are not probable in flight structure subject to sonic excitation, or

– Catastrophic failure is not probable if sonic fatigue cracking occurs

• Instructions for Continued Airworthiness– The data developed to demonstrate compliance

with this requirement forms the basis for the airframe instructions for continued airworthiness

LIGHTNING PROTECTIONLIGHTNING PROTECTION

• The Airplane Must be Protected Against Catastrophic Effects of Lightning– Electrical bonding– Design of components to preclude the effect of

a strike– Diverting electrical current

PROOF OF STRUCTUREPROOF OF STRUCTURE

• 25.303 through 25.307• Computed Loads - Limit Loads• Limit Loads Times Factor of Safety -

Ultimate Loads– Factor of safety - 1.5

Very low number - commercial machine design applications use 6 and up

Usage is justified by material and process controls imposed by Subpart D and maintenance programs required by operating rules> Part 91, 121, 125, 135


• Requirement– Limit load

No detrimental permanent deformation Deflections may not interfere with safe

operation– Ultimate load

Structure must be able to support the load for 3 seconds

– Dynamic testing may be used


• Compliance Demonstration– Static tests to limit load

May require ultimate load testing where limit load testing is determined to be inadequate

– Structural analysis May only be used if the structure conforms

to that for which this method has been shown to be reliable

DESIGN AND CONSTRUCTIONDESIGN AND CONSTRUCTION

• Material & Process Specifications– 25.603, 25.605, 25.613

• Special Factors– 25.619 - 25.625

• Design Criteria– 25.607 - 25.611, 25.651 - 25.735

• Special Considerations– 25.629 - 25.631, 25.843(a)

MATERIAL & PROCESS MATERIAL & PROCESS SPECIFICATIONSSPECIFICATIONS

• The Suitability and Durability of Materials Must - – Be established on the basis of experience or

tests– Conform to approved specifications

Ensure having the strength and other properties assumed in the design data

Take into account environmental conditions expected in service> Temperature> Humidity


• Manufacturing Processes– The method of fabrication used must produce

a consistently sound structure– If a fabrication process requires close control

to produce consistently sound results it must be performed under an approved process specification

– Each new fabrication method must be substantiated by tests


• Material Specifications– Material strength properties must be based on

enough tests of material meeting approved specifications to establish design values on a statistical basis

“A-basis” – 99% probability, 90% confidence “B-basis” – 90% probability, 90% confidence

– Effects of temperature must be considered where thermal effects are significant under normal operating conditions

SPECIAL FACTORSSPECIAL FACTORS

• The Factor of Safety of 1.5 Must be Multiplied by the Highest Pertinent Special Factor of Safety for Each Part of the Structure Whose Strength is– Uncertain– Likely to deteriorate in service– Subject to appreciable variability

Uncertainties in manufacturing process Uncertainties in inspection methods


• Casting Factor – Process Variables– Critical castings

Failure would preclude continued safe flight and landing or cause injury

1.25 to 1.5> Based upon testing and inspection

– Noncritical castings All others 1.0 to 2.0

> Based upon testing and inspection


• Fitting Factor – Uncertainties in Stress Analysis– Applied to fittings whose strength has not been

proven by limit and ultimate load tests– 1.15

• Fitting Factor – Wear and Deterioration– Seats, seatbelt fittings– 1.33

• Bearing Factor – Wear and Deterioration– Control surface hinges– 6.67


• Bearing Factor – Clearance Fits Subject to Vibration– Judgment

• Joints Subject to Angular Motion – Wear– 3.33– Not applicable to ball or roller bearings

DESIGN CRITERIADESIGN CRITERIA

• Fasteners– Locking devices

• Protection of Structure– Protection against loss of strength in service

due to any cause, including Weathering Corrosion Abrasion

– Provisions for ventilation and drainage


• Control Surfaces– Limit load tests required– Compliance with special factor requirements

must be shown by analysis or test• Control System Stops

– Must be able to withstand any load corresponding to design conditions for the control system

• Control system Limit Load Static Tests– Testing required in which

Each fitting, pulley and bracket is loaded Compliance with special factors may be by

analysis


• Landing Gear– Shock absorption tests

Limit drop tests> Landing load factors

Reserve energy absorption drop tests> 12 foot per second descent velocity

• Landing Gear Retracting Mechanisms– Loads from flight conditions, gear retracted– Loads from flight conditions in landing

configuration, gear retraction operating


• Landing Gear Doors– Design for yawing conditions

• Wheels and Tires– Requirements for load ratings

SPECIAL CONSIDERATIONSSPECIAL CONSIDERATIONS

• Aeroelastic Stability Requirements– Flutter, divergence, control reversal– Loss of stability and control as a result of

structural deformation– Must be shown by

Analysis Wind tunnel tests Ground vibration tests Flight tests Other means found necessary by the

Administrator

SPECIAL CONSIDERATIONSSPECIAL CONSIDERATIONS

• Aeroelastic Stability Requirements (Cont’d)– Aeroelastic stability envelope

Normal conditions> VD + 15%

Failure, malfunction & adverse conditions> VC + 15%> Failures, malfunctions & adverse conditions defined

– Flight test requirements• Bird Strike

– Empennage 8 pound bird at VC

Robert C. JonesMechanical Systems Branch


MECHANICAL SYSTEMSMECHANICAL SYSTEMS

MECHANICAL SYSTEMSMECHANICAL SYSTEMS

• Flight Controls

• Hydraulic Systems

• Landing Gear Systems

• Cabin Environmental Systems

• Cargo Fire Protection Systems

• Ice Protection Systems

FLIGHT CONTROL SYSTEMSFLIGHT CONTROL SYSTEMS

Flight Control Systems (25.629, .671, .672, .1309 et al)• Ensure airplane controllability for

– All flight and load conditions in flight envelope– Environmental conditions (temp, precip, salt, deice contamination, etc)

– In the presence of failures (including A/P) All single failures & combinations of

failures Pf > 10^-9 and certain dual failures Jams Pj > 10^-9

– Ensure availability of functions that rely on FC Stability: Flutter, speed, mach, dutch roll; load

allev. Safe pilot interface (feel systems, disconnects,

indications, warnings, motions, procedures)• Methods: Test, analysis redundancy, separation, monitoring,

maintenance


Safety Objectives• Provide control system capable of safely maneuvering airplane

through all phases of flight within the flight envelope and that has effective residual control for safe flight and landing after failures and jams.

• The system must be designed to allow to control airplane without exceptional piloting skill or strength even after failures.

• System design must account for human factors to ensure pilot has suitable warnings, can disconnect or override interfacing systems, and that movement of controls in the normal sense results in normal airplane response.

• Where automated functions (A/P, SAS, LAS) implemented thru flight controls ensure system has acceptable reliability, annunciation, disconnects, and that procedures are available to permit CSF&L.

• Ensure the airplane without engines remains controllable down to certain landing speeds.


Upcoming Improvements

Harmonized flight control rule (25.671/672) • Addresses NTSB recommendation for reliable

redundancy• Ensure that failures of dual redundant control

paths do not fail latent without meeting specific guidelines

HYDRAULIC SYSTEMSHYDRAULIC SYSTEMS

Hydraulic Systems (25.1309, 1435, 1438, 1461)

• Ensure hydraulics for critical & essential services

• Equipment req’d to meet specific pressure loads in combination with limit structural loads and to withstand 1.5 X design operating pressure load

• Fire safety requirements

• Integrity of pressure vessels

• Containment of failed rotors

• Methods: Test, analysis, separation, redundancy, monitoring, maintenance

HYDRAULIC SYSTEMSHYDRAULIC SYSTEMS

Safety Objective

• Ensure hydraulics for critical & essential services, as required, to allow continued safe flight and landing even after hydraulic failures

LANDING GEAR SYSTEMSLANDING GEAR SYSTEMS

Landing Gear Systems (25.721, 729, 735, 1309, JAR 25.745)

• Provide capability for airplane ground maneuvering,

• Braking/stopping, • Gear retraction and gear extension in the

air.


Safety Objective

• Provide capability for airplane ground maneuvering, braking/stopping, plus gear retraction and gear extension in the air

– Landing gear systems include nose and main gear retraction/extension mechanisms including doors, wheels, tires, brakes and brake controls (antiskid), steering, brake wear & temperature monitoring, and tire pressure indication systems


Note

• Worn Brake Rejected Take-Off (RTO)

– A DC-10 went off the runway. Brakes had been tested in a new condition for RTO in accordance with the certification rules in effect at that time. AD required airplanes over 75,000 pounds to perform a worn brake demonstration(dynamometer)

– Latest rule requires airplane demonstration for all gross weights

Cabin Environment (25.831, 25.832, 25.841, 25.1438, 25.1441, 25.1443, 25.1445, 25.1447, 25.1450, 25.1309)

• Ensure passengers and crewmembers have:

– an acceptable environment during normal operating conditions

– adequate protection to enable survival without permanent physiological damage after any system failure

• Methods: Test, analysis, redundancy, maintenance

CABIN ENVIRONMENTAL SYSTEMSCABIN ENVIRONMENTAL SYSTEMS

Safety Objective

• Provide the means to keep the occupants of the aircraft alive and comfortable

– Oxygen, pressurization, pneumatic, heating, ventilation, and air conditioning systems



• The pressurization and temperature controlled environments protect the occupants from the cold temperatures at high altitudes and provides an atmosphere with enough oxygen to maintain life

• The high operating altitudes of modern aircraft necessitate oxygen systems that can sustain life for a limited period of time should cabin pressurization fail

Cargo Fire Protection (25.851(b), 25.855, 25.857, 25.858, 1309)

• Ensure that - – Detection systems detect a fire before it

damages airplane structure & provides visual indication within 1 minute

– Built-in fire extinguishing system does not introduce a hazard to occupants or the airplane structure & is adequate to control any fire likely to occur

• Methods: Test, analysis, redundancy, maintenance

CARGO FIRE PROTECTION CARGO FIRE PROTECTION SYSTEMSSYSTEMS

Safety Objectives

• Provide safety features to detect/combat fires

• Minimize the impact of fire and extinguishing agent on occupants


• Cargo Compartments

– Requirements to keep hazardous quantities of smoke/flame from entering into crew/passenger compartments

– Most are required to have smoke/fire detectors and an annunciator in the flightdeck

• Fire Suppression

– Cargo compartment fires are not “extinguished,” they are “suppressed and controlled”

– The suppressing agent is Halon



• Information on Class D to C Cargo Compartments

– FAA eliminated Class D cargo compartments for future type certification from commercial transport airplanes March 19, 2001

Class D cargo compartments must meet the standards for Class C or Class E compartments

These changes came about because of a number of

accidents, including Valujet

ICE PROTECTION SYSTEMSICE PROTECTION SYSTEMS

Ice Protection (25.1419, 1403, 1309)

• Ensure Airplane Safety by:

– Detection ice or icing conditions– Anti-ice or deice capability– Windshield and probes heating – Provide acceptable flight characteristics for

intercycle ice and ice accreted on unprotected surfaces

• Methods: Test, analysis, redundancy, separations


Safety Objectives• For airplanes that intend to operate in icing conditions

the ice detection and protections systems must be designed to ensure timely activation and capability of ice protection system, the airplane must be shown to safely operate with ice accreted on unprotected surfaces and intercycle ice on protected surfaces, and the airplane must be shown safe for trajectories of shed ice to ensure they do not negatively impact propulsion, instruments, or structures

• Clear windshield in icing conditions• Instruments operable in icing conditions


• Developments– Definition of SLD conditions for certification.

Current FAR/JAR do not cover this condition. (rule in development)

– Detection of ice formations aft of the protected surfaces. Current FAR/JAR do not require this. (OPS rule in development)

– Ensuring stall margins met with intercycle ice and ice on unprotected surfaces (SFAR in work)

PART 25 EQUIPMENT RULESPART 25 EQUIPMENT RULES

Steve BoydSystems & Flight Crew Interface Branch


OVERVIEWOVERVIEW

• General Remarks• Equipment Installation Requirements• Safety Standards and Objectives• Operational Environment• Instruments• Electrical Systems• Lighting• Recording Systems

GENERAL REMARKSGENERAL REMARKS

• Subpart F addresses most systems installed in the airplane

• Examples include – avionics – flight and navigational equipment – environmental control – lighting– power generation

EQUIPMENT INSTALLATION EQUIPMENT INSTALLATION REQUIREMENTSREQUIREMENTS

• Overall Purposes – Establish safety standards for installed equipment

Equipment must perform its intended functions Regulate frequency of failures based on their

severity Protect aircraft and persons against effects of

environmental and operational hazards Provide means to alert the crew

– Standardize certain flight deck display information– Provide airworthiness standards for certain

equipment required by operating rules

SAFETY STANDARDS: PERFORM SAFETY STANDARDS: PERFORM INTENDED FUNCTIONINTENDED FUNCTION

• The equipment’s functionality, capability, and limitation must be deliberately incorporated, i.e. no hidden functionality (25.1301)

• Certain levels of reliability for safety-critical systems are required,…

• However, equipment is not expected to always work

• Therefore, the effects of failures are also regulated (25.1309)

SAFETY OBJECTIVESSAFETY OBJECTIVES

Catastrophic Effect

Minor Effect

Extremely Improbable

More Frequent

Reduced Crew Ability to Cope with Adversity

Improbable

• Failure effects are regulated by requiring an inverse relationship between the severity of the failures and their frequency of occurrence

SAFETY OBJECTIVESSAFETY OBJECTIVES (continued)(continued)

In addition…• Fail Safe Design = No single failure

can result in a catastrophic condition (AC25.1309-1A)


• The regulations governing system safety are based on the “fail-safe” design concepts which typically include:– Design integrity and quality (design practices)– System redundancy (protect from first failure)– Proven reliability (service experience)– Error tolerance (designer, maintainer, operator)– Flight/maintenance crew procedures (mitigate

failure effects)– Others (not listed for brevity)


• The safety objectives are defined at the airplane level, not at the components themselves [a component failure does not always result in a hazard to the airplane, crew, or occupants]

• To meet these objectives, the methods of compliance routinely involve qualifying components by rigorous industry-wide guidelines:– Hardware RTCA/DO-160D– Software RTCA/DO-178B

• Alerting is necessary to meet the overall safety objectives (25.1309 (c)) – When flight crews are expected in intervene to

mitigate the effects of failures– Alerting can be by design (warnings/cautions)

or by intrinsic characteristics (e.g. deterrent buffet)

• Lighted messages are standardized by color coding: red or Amber, depending on the hazard level and urgency (25.1322)


SAFETY OBJECTIVESSAFETY OBJECTIVES (end)(end)

• Certification Maintenance Requirements (CMR) are established during certification as an operating limitation of the Type Certificate (AC25-19)– CMR is failure finding task to detect safety-

significant latent system failures that, in combination with other failures, result in a hazardous or catastrophic condition

– CMR is not MSG-3 which are tasks that prevent failures

– CMR is not structural inspection required by 25.571, 25.1529, Appendix H25.4

THE OPERATING ENVIRONMENTTHE OPERATING ENVIRONMENT

• Effects due to operational and environmental conditions (internal and external) are considered – Specific rules for:

lightning protection (25.1316) ice detection and protection (25.1403, 1419) life support systems (25.1438-1453)

– Other conditions (altitude, temperature, rain, wind, vibration, glare, etc…) are considered in specific methods of compliance which typically involve testing

INSTRUMENTSINSTRUMENTS

• The regulations provide the minimum standards for displaying safety-critical information in the flight deck (25.1303, 1305)

• Certain instruments must be installed– Safety-critical flight and navigation

instruments (specific navigation systems are required by operating rules)

– Powerplant instruments• The “basic T” arrangement (25.1321)


• Specific regulations levied against flight critical system to ensure:– Safety of design (under failure conditions, for

flammability, system status indications, etc.)– Human factors issues (control accessibility,

consistency of operation, consistent use of color, etc.) have been addressed

– Adequate means to detect system failures – Adequate system capacity (for electrical

power)


• General requirements levied against flight critical instruments ensure:– Means are provided to connect required

instruments to opposite side of cockpit– Display of information essential to safety of

flight will remain available to pilots after single failure

– Other systems may not be connected to these flight critical systems, unless provisions are made to ensure correct operation after failure

AIRSPEED INDICATING (25.1323)AIRSPEED INDICATING (25.1323)STATIC PRESSURE (25.1325)STATIC PRESSURE (25.1325)

• Other specific instrumentation requirements intended to deal with past problem areas:– System arrangement to prevent malfunction due to

entry of moisture, dirt, or other substances– Heated to prevent malfunction due to icing – Redundant systems separated to prevent single

event (e.g., birdstrike) from disabling multiple systems

– Positive drainage to avoid corrosion, correct use of materials, correct installation to avoid chafing

AUTOPILOT/FLIGHT DIRECTOR AUTOPILOT/FLIGHT DIRECTOR SYSTEMS (25.1329)SYSTEMS (25.1329)

• Must be able to be disengaged quickly and positively to prevent interference with pilot control of airplane

• Must be designed to prevent hazardous loads on airframe or hazardous flight path deviations during normal flight or failure condition

• Must be designed to provide positive and unambiguous annunciation of current operating mode

• Human factors issues (operation of controls, location of displays and controls, etc.)

POWERPLANT INSTRUMENTS POWERPLANT INSTRUMENTS (25.1337)(25.1337)

• Provides installation requirements for the instruments required by other sections– Minimize hazards from escape of flammable

fluids– Ensure proper calibration of fuel quantity

indication systems– Minimize affects of fuel flowmeter

malfunctions– Other specific issues associated with oil

quantity, propeller position, and fuel pressure indication systems

ELECTRICAL SYSTEMSELECTRICAL SYSTEMS

• General Requirements

• Generating Systems

• Distribution System

• Circuit Breakers

GENERAL REQUIREMENTSGENERAL REQUIREMENTS

• The airplane must be capable of operation without normal electrical power sources at maximum altitude for at least 5 minutes (25.1351d)

• Electrical equipment, controls and wiring must be installed to ensure non-interference with other electrical units and systems essential to safe operations (25.1353a)

• Electrical cables must be grouped, spaced and routed to minimize damage to essential systems due to faults in heavy current-carrying cables (25.1353b)

GENERAL REQUIREMENTSGENERAL REQUIREMENTS

• Electrical Systems Laboratory Tests (25.1363)– system should have a high degree of fidelity

with actual equipment installed on the airplane– for flight conditions not simulated adequately

in the laboratory, flight tests must be made example: effect of zero g and negative g’s

on generator function

GENERATING SYSTEMS (25.1351)GENERATING SYSTEMS (25.1351)

• Electrical Loads analysis determines the generating capacity and number and kind of power sources

• No failure of a power source can create a hazard or impair the ability of remaining sources to supply essential loads

• There must be a means to disconnect power sources from the system and indicate power available

BATTERIES (25.1353C)BATTERIES (25.1353C)

• Most aircraft need a battery to power critical systems or start the auxiliary power unit in case normal generator power is lost in flight

• Battery requirements include:– temperature and pressure safeguards– protection from explosion and toxic gas emissions– meet 5 minute loss of primary power requirement– charge rate, temperature monitored with

associated warning to crew and ability to disconnect

CIRCUIT PROTECTION (25.1357)CIRCUIT PROTECTION (25.1357)

• Circuit breakers or fuses are required to protect wiring and airplane power busses– automatic devices required to minimize hazard

to airplane in event of wiring faults– protective devices necessary for generating

system– if resetting is required for safety of flight,

circuit breaker must be located and identified so it can be easily reset in flight

LIGHTING REQUIREMENTSLIGHTING REQUIREMENTS

• External requirements include:– Position lights (red, green, white on tail)

(25.1385, 1387, 1389)– Anti-collision lights (25.1401)– Wing ice detection lights (25.1403)– Landing lights (25.1383)

• Specific requirements for coverage, color, position and intensity (25.1389, 1391, 1393, 1395, 1397)

LIGHTING REQUIREMENTSLIGHTING REQUIREMENTS

• Internal lighting requirements include:– means provided to control intensity (25.1381)– meet intended function (25.1301)– emergency lightning for evacuation (25.812)

• Cockpit lighting evaluation by pilots for all operational conditions

• No requirements for cabin lights, except for emergency lighting

RECORDING SYSTEMSRECORDING SYSTEMS

• Recording systems must not impact the safe operation of the airplane and are mandated by the operating rules (91.609 c,e)

• Design and installation requirements addressed in Part 25, subsection F– Cockpit Voice Recorder (CVR)– Flight Data Recorder (FDR)

• Additional requirements in operating rules (121.359, 121.343)

MISCELLANEOUS EQUIPMENT MISCELLANEOUS EQUIPMENT REQUIRED BY OPERATING RULESREQUIRED BY OPERATING RULES

• Airworthiness standards for certain equipment required by operating rules are provided– Windshear systems (121.358, AC25-12)– Protective breathing equipment (25.1439)– Oxygen equipment (25.1441-1453)– Terrain Awareness & Warning (TAWS)

(121.354, AC25-23)– Traffic Alert & Collision Avoidance System

(TCAS) (121.356)

ENGINES AND APU’SENGINES AND APU’S

Mark FulmerManager, Engine Certification Office

Engine and Propeller Directorate

FUNDAMENTAL CERTIFICATION CONCEPTSFUNDAMENTAL CERTIFICATION CONCEPTSENGINES AND APU’SENGINES AND APU’S

• Safety is defined at the Aircraft level

– Engine and APU Contributors

Burst

Fire

Loads

Loss of Thrust Control

Toxic Products in Bleeds

In-flight Shutdown

Propeller Release

Typical averageby PAH type

Wide variationsubjective criteria

Priority

ResourceExpenditure(degree ofattentionpaid)

THE OLD WAYResources Expended on Initial & Ongoing Evaluation (Type & Production)

THE OLD WAYResources Expended on Initial & Ongoing Evaluation (Type & Production)

No Distinction for Same Production Approval Holder (PAH) types PMA/TSO/PC)

{

THE NEW WAYResources Expended on Initial & Ongoing Evaluation

(Type & Production)

THE NEW WAYResources Expended on Initial & Ongoing Evaluation

(Type & Production)

Smaller variationdefined by resourcetargeting

ResourceExpenditure(degree ofsafety basedattentionpaid)

Priority

Old Avg.

Non-PriorityNon-Critical

Designees &Self Audit

PriorityNon-Critical

PI/PE Evaluations

PriorityCritical

ACSEP & ProductSpecific Evaluations

Focus

Eval. Method

System AdequacyCriteria

{{{

Determined by: - SVC Exper Safety Data - Product Safety Assessment

Causal Factors of Disk Causal Factors of Disk FracturesFractures

Accident (level 4)

Part Fractures

Hazardous events:~ 16 per 100 M flights

All uncontained:~ 32 per 100 M flights

low cyclefatigue

high cyclefatigue

manufact.defect

materialdefect

maint. &overhaul

fretting/rubbing

erosion/corrosion

bearingfailure

overspeed overtemp FOD

ForgingMachiningPeening

TitaniumInconelSteelOther

Assembly errorInspectionRepairtroubleshooting

Loss of diskcooling,Limitationexceeded

Shaft failureFuel ControlClosed VSVs

Examples

Opportunities

~ 5 per 100 Million Flights

Opportunities

DesignProd.Maint.

BirdsA/C ice shedBlue iceBMOD


• Some common considerations

– Likely single and multiple failures

– Likely improper operation

– Likely improper maintenance

– Likely inservice damage

– Minimize and cover latent failures

– Human factors assessed


• Burst

– Minimize failures that can release debris, particularly high energy debris

– Contain failures where possible

– Uncontainable failures are predictable

– Effects on aircraft minimized (redundancy, isolation, shielding)


• Fire– Minimize occurrence and spread

Contain flammable fluids

> Assess structural integrity and materials of components and fire wall

Isolate ignition sources

Control usage of flammable materials such as Titanium and Magnesium

Coordination with aircraft installation to minimize effects


• Loads– Ultimate and limit capability defined

Mounts Major load carrying structure

– Vibratory (internal and external effects) Component criticals and induced

– Failure conditions Instantaneous, rundown, windmilling

– Engine induced loads coordinated with aircraft installation


• Loss of Thrust Control – Control system reliability and safety

assessment (hardware and software)

– Redundancy channels, mode, models, hydro-mechanical

backup

– Auto-shutdown for APU’s

– Limiting topping, overspeed, overtemp

– Fail safe options


• Toxic Products in Bleeds

– Bleed air quality testing

– HazMats and VOC assessment

– Minimize ingress for likely failures

– Aircraft level isolation


• In-flight Shutdown – Reliability and durability

Random independent vs. common cause threat Damage tolerance ETOPS Control system time limited dispatch

– Environmental Weather, birds, HIRF, lightning

– Stability Fan and compressor stall Combustor stability

– Human factors in operations and maintenance


• Propeller Release

– Propeller mount flange and shaft loads

– Propeller installation and flight strain survey evaluated for suitability


• Outcomes of Certification– Ratings and Operating Limitations

Power Rotor speeds Temperatures and pressures (gas path, fuel,

oil, etc.)

– Installation Requirements Component temperatures Loads (steady & vibratory) Inputs/Outputs


• Outcomes of Certification– Operating instructions

Altitude, attitude, speed, temperature Procedures (in-flight relight, environmental,

ground handling, etc.)

– Airworthiness Limits Component life, inspections, maintenance

– Instructions for Continued Airworthiness On-wing preventative maintenance and

off-wing overhaul


• Production Certification

– Production process definition, process controls, defect characterization, inspectability, surveillance

• Operational and Maintenance Certifications

– Based on ability to adhere to type certification data, limitations, and conditions

• Ongoing Management of Production, Operability and Maintainability

FA ACT SECTION 603FA ACT SECTION 603

• To be eligible for an airworthiness certificate, an aircraft must:

– Conform to its type certificate, and

– Be in a condition for safe operation

• Type Certificate (FAR 21.41) includes the type design (FAR 21.31) plus operating limitations, TCDS, and applicable FAR compliance conditions and limitations

• Repair Stations must perform work in accordance with the manufacturers ICA (FAR 43.13a), an aircarrier's manuals (FAR 145.2) or other FAA approved data.

• Maintenance may be conducted using other methods, techniques and practices acceptable to the Administrator that accomplish the same end result with respect to airworthiness i.e.; conformity to the type design and safe for operation

• Repairs, alterations, or deviations from the Manufacturers ICA which are major require FAA approved data

• Maintenance must return the product to either its original or properly altered configuration (FAR 43.13b)

PERFORMANCE OF MAINTENANCE PERFORMANCE OF MAINTENANCE AND ALTERATIONAND ALTERATION

• In Closing:

– Don’t confuse compliance with safe nor non-compliance with unsafe

– There is no such thing as an isolated event


POWERPLANT INSTALLATIONSPOWERPLANT INSTALLATIONS

Kathrine RaskSenior Engineer, Propulsion Branch

Seattle Aircraft Certification Office

PROPULSION SYSTEMPROPULSION SYSTEM

• Overview– System Definitions

– Fundamental Certification Concepts

– Fuel Systems

– Engine Ice Protection

– Thrust Reverser

– Engine Operating Characteristics

– Fire Protection

– Uncontained Engine Failure

– Powerplant Instruments

SYSTEM DEFINITIONSSYSTEM DEFINITIONS

• Multi-Engine Installation– Engines are Part 33 certified

Objective is “stand alone” type certificate; generally not airframe specific

• Auxiliary Power Unit (APU) Installation– APU’s qualified to technical standard order

Also “stand alone” certification objective

• Fuel System – Tanks, pumps, plumbing, wiring, etc.

§§ 25.901(a), 25.903

FUNDAMENTAL CERTIFICATION FUNDAMENTAL CERTIFICATION CONCEPTSCONCEPTS

• No Single Failure or Probable Combination of Failures will Jeopardize Safe Operation– A single failure is assumed without

consideration as to its probability of failing– If a failure event cannot be readily detected, it

is counted as a latent existing failure in addition to the first failure

– “Probable” - expected or foreseeable Term often confused with 25.1309

terminology; quantitatively means “not extremely improbable”

§ 25.901(c)

FUNDAMENTAL CERTIFICATION FUNDAMENTAL CERTIFICATION CONCEPTSCONCEPTS

– “Jeopardize safe operation” Continued safe flight and landing from brake

release through ground deceleration to stop Safe flight is determined by both qualitative

and quantitative analysis Consider service experience of similar failures

§ 25.901(c)

FUNDAMENTAL CERTIFICATION FUNDAMENTAL CERTIFICATION CONCEPTS CONCEPTS

• No Single Failure or Probable Combination of Failures will Jeopardize Safe Operation– Accomplished By

Isolation Independence Redundancy Reliability

– Four Exceptions To Rule Uncontained Engine Failures Combustor Case Burn Through Propeller Failure Certain Structural Failures

§§ 25.901(c), 25.903(b), 25.903(d)(1), 25.905(d)

FUEL SYSTEMSFUEL SYSTEMS

• Fuel System Independence/Redundancy• Fuel Flow

– Normal operation– Hot/cold weather, negative “G,” gravity feed

• Lightning Protection• Crashworthiness• Failure Modes

– Ignition sources/flammability – Function of automated fuel system

§§ 25.943, 25.951-25.1001

FUEL SYSTEMFUEL SYSTEM

• New Outlook on Fuel System Safety– Part 21 Special Federal Aviation Regulation

Retroactive design review of in-service airplanes

– New Part 25 Regulation Changes Improved safety analysis Minimized fuel tank flammability

– Operating Rule Changes Mandate improved maintenance

SFAR No. 88; §§ 25.981, 91.410, 121.370, 125.248, 129.32

ENGINE ICE PROTECTIONENGINE ICE PROTECTION

• Engine Installation Shall Continue to Operate in Severe Environmental Conditions– Review ice accumulations on engine, inlet, and

other airframe surfaces that could be ingested Freezing fog on ground Falling and blowing snow on ground Late activation of ice protection by crew in

flight Fan ice shedding and procedures

– No engine icing limitations Engine power/thrust always required to exit

inadvertent icing conditions

§ 25.1093

THRUST REVERSERTHRUST REVERSER• Demonstrate compatibility with engine

• Demonstrate compatibility with airplane – Significant change in philosophy since the Lauda 767 accident

Exposed vulnerability to certain aircraft during high speed flight

Long Strut/Low Mount Short Strut/High Mount

T/R pattern under wing - no stall T/R pattern over wing - stall

THRUST REVERSERTHRUST REVERSER

• Two Options to Meet Part 25 Safety Intent:– To demonstrate that the airplane must be

controllable under any possible position of the thrust reverser

Thorough flight test controllability demonstration

Demonstrate operable reverser can be restored to the forward thrust position

Minimize potential for in-flight deployment

§ 25.933


• Two Options to Meet Part 25 Safety Intent (continued):– To demonstrate the possibility of an inflight

thrust reverser deployment will not occur within the life of the airplane fleet

Rigorous qualitative and quantitative analysis with more conservative assumptions

Typically results in three independent thrust reverser restraints

Review minimum dispatch configurations


• Maintenance has played a significant role in the majority of inflight thrust reverser incidents – Review safety analysis assumptions to ensure they

are tolerant to human error– Review general thrust reverser maintenance

procedures– In depth review of thrust reverser lock-out

configuration and procedures

• Vast majority of in-service thrust reverser uncommanded deployments resulted from improperly de-activating system associated with MEL activity

ENGINE OPERATING ENGINE OPERATING CHARACTERISTICSCHARACTERISTICS

• Engines should continue to safely operate throughout the airplane flight envelope

• Engine operation demonstrated at airplane’s limits of :

– Ambient temperature

– Altitude/airspeed/angle of attack

– Tailwind/crosswind

– Rapid and slow power lever movements

– Mechanical/electrical loading

§§ 25.939, 25.931

POWERPLANT FIRE PROTECTIONPOWERPLANT FIRE PROTECTION

• General intent is to provide redundant design: – Minimize potential for fire

Ventilation required to minimize potential of flammable vapor

Managing zone temperatures and sources of ignition

– Minimize effects/duration if a fire should occur Fire walls Quick acting detectors Flammable fluid shut off provisions Drainage provisions Extinguishing

§§ 25.863-25.869, 25.1181-25.1207

UNCONTAINED ENGINE FAILUREUNCONTAINED ENGINE FAILURE

DC-10; 1973

B-747; 2000


• Uncontained engine failure threat too great to be completely addressed by failsafe philosophy – Some of the threat addressed by prescriptive

requirements Differential compartment loads Damage tolerant structure Decompression

§§ 25.365(e)(1), 25.571(e)(2)-(3), 25.841(a)(3), 25.903(d)(1)


– Remainder of airplane threat minimized in the event of an uncontained engine or APU failure

Isolation> hydraulic check valves> flammable fluid shut-off provisions & dry bays

Redundancy & Separation> hydraulic line, flight control wires/cables & electric

power> flammable fluid shut-off valves

Shielding> critical structure & systems> auxiliary fuel tanks> APU containment devices

POWERPLANT INSTRUMENTSPOWERPLANT INSTRUMENTS

• Intent is to provide indication of engine parameters, limits, and failures to enable the crew to always maintain control of engine – Limit exceedances (protect rotor integrity)– Fault enunciation - critical failures

Messaging system consistent with flight deck philosophy

Minimize flight crew workload– Pop-up displays– Standby indication – Trend monitoring

§§ 25.1305

OTHER SYSTEM REQUIREMENTSOTHER SYSTEM REQUIREMENTS

– Propeller installation– Oil system– Thrust augmentation– Starting– Component cooling

– Controls– APU– Performance– Powerplant accessories– Inlets/Exhaust

All follow the fundamental concept of fail-safe and isolation

• Part 25 also addresses:

CABIN SAFETYCABIN SAFETYCABIN SAFETYCABIN SAFETY

Frank TiangsingManager, Airframe/Cabin Safety Branch


DEFINITIONDEFINITIONDEFINITIONDEFINITION

• Cabin Safety, the discipline that deals with:– Occupant protection/survival

– Escape from crashes or other emergency events

Mechanical Systems

Cabin Safety Airframe

Electrical Systems

Operations (Flight Standards)

MAIN ELEMENTSMAIN ELEMENTSMAIN ELEMENTSMAIN ELEMENTS

• Occupant protection

• Evacuation

• Fire protection

• Emergency equipment

OCCUPANT PROTECTIONOCCUPANT PROTECTION

• Occupant protection is provided by having:– Seats approved to static and dynamic loads

(§§ 25.561, 25.562, 25.785) – Items of mass retained (§ 25.789)– Padding on projecting objects (§ 25.785(k))– Handholds along aisles (§ 25.785(j))– Slip resistant floors (§ 25.793)– Access to oxygen during a decompression event

(§ 25.1447)


• Static testing of seats– Seats are tested to loads in the forward, aft,

sideward, up and down directions– Maximum loads from the ground, flight and

emergency landing conditions are applied


• Dynamic testing of seats – Two test conditions

16g forward load 14g downward load

– Includes occupant injury criteria Head Injury Criteria (HIC) Lumbar load Femur load

– TSO-C127 prescribes minimum performance standards for dynamically tested seats



• EVACUATION

• Fire protection


EVACUATIONEVACUATION

Evacuation addresses the means for occupants to safely travel from their seats to the ground or water


• Effective evacuation is accomplished by providing: – Appropriate type and number of exits (§ 25.807) – Access to exits (§ 25.813)– Assist means from the aircraft to ground or water

(§ 25.810, TSO C69c)


• Effective evacuation is accomplished by providing: – Emergency lighting (§ 25.812)– Emergency evacuation demonstration (§ 25.803, App. J)– Ditching capability (§ 25.801)



• Evacuation

• FIRE PROTECTION


FIRE PROTECTIONFIRE PROTECTION

• Interior fire protection is accomplished by addressing the following areas:– Interior materials (§ 25.853, App. F)

Bunsen burner test (Part I) Seat cushion test (Part II) Heat release test (Part IV) Smoke emission test (Part V)

– Cargo compartments (§ 25.855, App. F) Bunsen burner test Oil burner test for Class C compartment liners (Part

III)

FIRE PROTECTIONFIRE PROTECTION

– Lavatories (§§ 25.853(h), 25.854) Waste receptacles

> Must have built-in fire extinguishers> Must be capable of containing fire

Smoke detectors are required – Portable fire extinguishers must be distributed

throughout the aircraft (§ 25.851)



• Evacuation

• Fire protection

• EMERGENCY EQUIPMENT

EMERGENCY EQUIPMENTEMERGENCY EQUIPMENT

• Emergency Equipment Required by Part 25 – Fire extinguishers, oxygen bottles, floatation seat

cushions or life vests (§§ 25.851, 25.1415, 25.1447, 121.333(e))

– Overwater operation: life rafts, life vests, survival kits, emergency transmitters, life lines (§ 25.1415)

• Emergency Equipment Required by Part 121– Megaphones, first aid kits, smoke hoods, crash ax,

flashlights (§§ 121.309, 121.337, 121.549)

EMERGENCY EQUIPMENTEMERGENCY EQUIPMENT

• Emergency equipment must be: – Readily accessible (§ 25.1411(a))– Reasonably distributed and arranged so that

its location is obvious, well identified and appropriate for its intended use (§§ 25.851(a), 25.1411)

– Protected from inadvertent damage (§25.1411(b))

HUMAN FACTORS IN PART 25HUMAN FACTORS IN PART 25

Steve BoydAirplane & Flight Crew Interface Branch


• Definition (unofficial) - Human Factors, as it applies to aircraft certification:– The application of scientific theory, principles, data

and methods... – about human abilities, limitations, and other

characteristics... – to the establishment of minimum safety-related

design requirements for flight crew interfaces, tasks, and procedures,...

– and then ensuring that those requirements are met,– in order to promote overall system performance and

safety

HUMAN FACTORS IN PART 25HUMAN FACTORS IN PART 25

• We base the requirements on knowledge and/or assumptions about:– The “human” capabilities and limitations of the

people who will fly the airplanes– Their level of training– Their roles and responsibilities– The demands of the mission

• Note: Requirements for items 2 and 3 are contained in the operating rules

UNDERPINNING FOR THE CREW UNDERPINNING FOR THE CREW INTERFACE REQUIREMENTSINTERFACE REQUIREMENTS

PRIMARY HF AREASPRIMARY HF AREAS

• Human factors issues are integrated into the rules in various subparts

• Main areas include:– The controls and displays that the pilots use– The physical geometry of the flight deck– Integrated aspects of the flight crew interfaces– The evaluation of performance and handling

qualities

COMPETING REQUIREMENTSCOMPETING REQUIREMENTS

All controls reachable,

displays readable

Space necessary for controls and

displays

Situation Awareness

Information Overload

Commonality

Additional functionality

16g seats

External vision Short Pilots

Weight. Panel space

Comfortable seats

Tall Pilots

CONTROLS AND DISPLAYSCONTROLS AND DISPLAYS

• Specific controls and displays are called out for certain functions

• Some are based on “assumed” pilot responsibilities

• Some are required to deal with failures– Driven by failure modes and effects– Pilot actions are intended to mitigate the

failure effects

CONTROLS AND DISPLAYSCONTROLS AND DISPLAYS

• Design to support pilot performance and reduce errors in the use of controls/displays– Arrangement - convenient accessibility and use,

no confusion, standardization– Direction of movement - matches the function– Control shape - standardization for certain

controls– Control labeling - except when function is

obvious– Preventing inadvertent activation - location,

guarding– Color coding - standardization for alerts/limits

FLIGHT DISPLAY FLIGHT DISPLAY ARRANGEMENTARRANGEMENT

• The technology and formats change, but….

Airspeed

Heading

Altitude

Attitude

FLIGHT DECK GEOMETRYFLIGHT DECK GEOMETRY

• Accommodate a range of pilot sizes– Short pilots can reach everything they need– Tall pilots can fit in the flight deck

• Pilots can see what they need to see– Installation location of the displays/controls– Windows provide adequate visibility

• Reflections and glare• Emergency egress

INTEGRATION ASPECTS OF THE INTEGRATION ASPECTS OF THE FLIGHT DECKFLIGHT DECK

• Workload– Workload must be acceptable for the minimum

flight crew– No unreasonable concentration or fatigue

• Crew response to failures • Environmental conditions

– Noise and vibration– Lighting

• Intended function - assessed in context

EVALUATION OF PERFORMANCE EVALUATION OF PERFORMANCE AND HANDLING QUALITIESAND HANDLING QUALITIES

• HF considerations are embedded in numerous requirements related to performance and handling qualities. Examples:– ...can be “consistently executed in service by

crews of average skill.”– …may not “require exceptional piloting or

alertness.”– “Reasonably expected variations in service from

the established takeoff procedures… may not result in unsafe flight characteristics…”

• Requirements are based on experience– Human performance “margins” are usually in

guidance material• Test pilots are the key players in evaluating

performance/HQ– Subjective assessment (including consideration of

line pilot capabilities and line operations)– Performance data - measuring airplane

performance with pilots in the loop– Close coordination between Certification and

Flight Standards (Aircraft Evaluation Group) pilots

EVALUATION OF PERFORMANCE EVALUATION OF PERFORMANCE AND HANDLING QUALITIESAND HANDLING QUALITIES

federal aviation administration transport airplane and engine safety requirements a general overview...

Documents

flight envelope slide

flight test goal

cheney flight

museum of flight

flight testing

boyd slide

mac slide

subpart g slide