FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceMedium
An airplane's positive limit load factor is 3.8G, and FAA certification standards require a structural safety factor of 1.5 beyond the limit load. At approximately what load factor would structural failure be expected to occur?
- A5.7G
- B3.8G
- C4.5G
- D7.6G
Show answer & explanationAnswer & explanation
Correct answer: A. 5.7G
The ultimate load factor equals the limit load factor multiplied by the certification safety factor: 3.8G x 1.5 = 5.7G. Loads between the limit (3.8G) and ultimate (5.7G) values may cause permanent deformation but structural failure is expected only at or beyond the ultimate load factor.
Why the other options are wrong
- B. 3.8G is only the limit load factor, not the failure point.
- C. This does not correctly apply the 1.5 safety factor multiplier.
- D. This overstates the safety margin; 7.6G would require a factor of 2.0, not 1.5.
Limit vs Ultimate Load Factor
The limit load factor is the maximum load an airplane can sustain without permanent deformation; the ultimate load factor (limit x 1.5 safety factor) is the point at which structural failure is expected.
- Ultimate load factor = limit load factor x 1.5
- Between limit and ultimate: possible permanent deformation, not failure
- Certification standards require this built-in safety margin
Memory trick: Limit bends it, ultimate (1.5x) breaks it.