Crashworthy Design ofCrashworthy Design ofMilitary RotorcraftMilitary Rotorcraft

Presented by:Presented by:

Dr. Akif BolukbasiDr. Akif BolukbasiSenior Technical FellowSenior Technical FellowPhone: (480) 891-5111Phone: (480) 891-5111

E-mail: akif.o.bolukbasi@boeing.comE-mail: akif.o.bolukbasi@boeing.com

Systems Approach to Crashworthy DesignSystems Approach to Crashworthy Design

Key SubsystemsKey Subsystems

• Landing GearsLanding Gears• Airframe StructureAirframe Structure• Seats & Restraint SystemsSeats & Restraint Systems• Fuel SystemsFuel Systems

Military Rotorcraft Crash EnvironmentMilitary Rotorcraft Crash Environment

Vertical Velocity Longitudinal Velocity Impact Terrain

Military Rotorcraft Crashworthiness Design CriteriaMilitary Rotorcraft Crashworthiness Design Criteria(MIL-STD-1290)(MIL-STD-1290)

Condition Number

Impact Direction(Aircraft Axes)

Velocity ChangeΔ ( / )V ft sec

ObjectImpacted

1 Longitudinal( )cockpit

20

2 Longitudinal( )cabin

40RigidVerticalBarriers

3 *Vertical 424 , **Lateral Type I 255 , ***Lateral Type II 30

RigidHorizontalBarriers

6 *Combined high angleVertical

Longitudinal4227

RigidHorizontalSurface

7 Combined low angleVertical

Longitudinal14100

PlowedSoil

Military Rotorcraft Crashworthiness Design CriteriaMilitary Rotorcraft Crashworthiness Design Criteria(Performance Requirements)(Performance Requirements)

ConditionNumber

ImpactDirection

Percentage VolumeReduction

OtherRequirements

1 Longitudinal(Cockpit)

No serious hazard topilot/copilot

Does not impedepost-crash egress.Engine, transmission,and rotor systemintact and in place

2 Longitudinal(Cabin)

15% maximum lengthreduction forpassenger/troopcompartment

Inward buckling ofside walls should notpose hazard tooccupants or restricttheir evacuation

3 Vertical 15% maximum heightreduction in cockpitand passenger/troopcompartment

Acceleration loadsnot injurious

4 & 5 Lateral 15% maximumwidth reduction

Lateral collapse ofoccupied areas nothazardous, noentrapment of limbs.

6 CombinedHigh Angle

No serious hazard tooccupant due tocockpit/cabinreduction

7 CombinedLow Angle

No serious hazardto occupant

Military Rotorcraft Crashworthiness Design CriteriaMilitary Rotorcraft Crashworthiness Design Criteria(Major Mass Item Retention Strength)(Major Mass Item Retention Strength)

(1) Applied Separately:

Longitudinal +/- 20gVertical +20g / -10gLateral +/- 18g

(2) Applied Simultaneously

Longitudinal +/- 20g +/- 10g +/- 10g Vertical +10g / -5g + 20g / -10g +10g / -5g Lateral +/- 9g +/- 9g +/- 18g

Vertical Impact Design RequirementsVertical Impact Design Requirements

CrashCrash

• Sink rates 26 fps (civil), 42 fps (military)Sink rates 26 fps (civil), 42 fps (military)

• Damage to the fuselage and mission equipment becomes Damage to the fuselage and mission equipment becomes unavoidable. The emphasis is on protecting the occupantsunavoidable. The emphasis is on protecting the occupants from injury.from injury.

• The fuselage may undergo large deformations but should The fuselage may undergo large deformations but should maintain a livable volume for occupants.maintain a livable volume for occupants.

• Post crash fires are minimized using crashworthy fuel systems.Post crash fires are minimized using crashworthy fuel systems.

Landing GearsLanding Gears

Normal LandingNormal Landing

• Sink Rates 8 - 10 fpsSink Rates 8 - 10 fps

• No yielding of the landing gear (military)No yielding of the landing gear (military)

Hard LandingHard Landing

• Sink rates 10 fps (civil), 20 fps (military)Sink rates 10 fps (civil), 20 fps (military)

• Emphasis on preventing fuselage and mission equipment damageEmphasis on preventing fuselage and mission equipment damage

• Plastic deformation or damage to the landing gear is acceptablePlastic deformation or damage to the landing gear is acceptable

Effect of Roll and Pitch RequirementsEffect of Roll and Pitch Requirements

Landing Gear TestingLanding Gear Testing

Skid Landing GearsSkid Landing Gears

Military Rotorcraft Crashworthiness Design CriteriaMilitary Rotorcraft Crashworthiness Design Criteria(Seats)(Seats)

Crashworthy Seat TestingCrashworthy Seat Testing

Dynamic Test #1 (Fwd & Down) Dynamic Test #2 (Fwd & Side)

Cost-Benefit Trade Study for Cost-Benefit Trade Study for Crashworthy Rotorcraft DesignCrashworthy Rotorcraft Design

ConclusionsConclusions

• Airframe protective shell to maintain livable volume.

• Adequate tie-down strength for occupants, cargo, and other heavy mass items.

• Non-injurious occupant acceleration environment.

• Delethalized interior to eliminate occupant secondary strike hazards.

• Elimination or delay of post-crash fire.

• Adequate emergency escape and rescue provisions.