Crashworthy Design of
Military Rotorcraft
Presented by:
Dr. Akif Bolukbasi
Senior Technical Fellow
Phone: (480) 891-5111
E-mail: akif.o.bolukbasi@boeing.com
Systems Approach to Crashworthy Design
Key Subsystems
• Landing Gears
• Airframe Structure
• Seats & Restraint Systems
• Fuel Systems
Military Rotorcraft Crash Environment
Vertical Velocity
Longitudinal Velocity
Impact Terrain
Military Rotorcraft Crashworthiness Design Criteria
(MIL-STD-1290)
Condition
Number
1
2
3
4
5
6
7
Impact Direction
(Aircraft Axes)
Longitudinal
(cockpit)
Longitudinal
(cabin)
Vertical*
Lateral, Type I**
Lateral, Type II***
Combined high angle*
Vertical
Longitudinal
Combined low angle
Vertical
Longitudinal
Velocity Change
V (ft/sec)
20
Object
Impacted
42
27
Rigid
Vertical
Barriers
Rigid
Horizontal
Barriers
Rigid
Horizontal
Surface
14
100
Plowed
Soil
40
42
25
30
Military Rotorcraft Crashworthiness Design Criteria
(Performance Requirements)
Condition
Number
1
Impact
Direction
Longitudinal
(Cockpit)
Percentage Volume
Reduction
No serious hazard to
pilot/copilot
2
Longitudinal
(Cabin)
15% maximum length
reduction for
passenger/troop
compartment
3
Vertical
4&5
Lateral
15% maximum height
reduction in cockpit
and passenger/troop
compartment
15% maximum
width reduction
6
Combined
High Angle
7
Combined
Low Angle
No serious hazard to
occupant due to
cockpit/cabin
reduction
No serious hazard
to occupant
Other
Requirements
Does not impede
post-crash egress.
Engine, transmission,
and rotor system
intact and in place
Inward buckling of
side walls should not
pose hazard to
occupants or restrict
their evacuation
Acceleration loads
not injurious
Lateral collapse of
occupied areas not
hazardous, no
entrapment of limbs.
Military Rotorcraft Crashworthiness Design Criteria
(Major Mass Item Retention Strength)
(1) Applied Separately:
Longitudinal
Vertical
Lateral
+/- 20g
+20g / -10g
+/- 18g
(2) Applied Simultaneously
Longitudinal
Vertical
Lateral
+/- 20g
+10g / -5g
+/- 9g
+/- 10g
+ 20g / -10g
+/- 9g
+/- 10g
+10g / -5g
+/- 18g
Vertical Impact Design Requirements
Crash
• Sink rates 26 fps (civil), 42 fps (military)
• Damage to the fuselage and mission equipment becomes
unavoidable. The emphasis is on protecting the occupants
from injury.
• The fuselage may undergo large deformations but should
maintain a livable volume for occupants.
• Post crash fires are minimized using crashworthy fuel systems.
Landing Gears
Normal Landing
• Sink Rates 8 - 10 fps
• No yielding of the landing gear (military)
Hard Landing
• Sink rates 10 fps (civil), 20 fps (military)
• Emphasis on preventing fuselage and mission equipment damage
• Plastic deformation or damage to the landing gear is acceptable
Effect of Roll and Pitch Requirements
Landing Gear Testing
Skid Landing Gears
Military Rotorcraft Crashworthiness Design Criteria
(Seats)
Crashworthy Seat Testing
Dynamic Test #1 (Fwd & Down)
Dynamic Test #2 (Fwd & Side)
Cost-Benefit Trade Study for
Crashworthy Rotorcraft Design
Conclusions

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.