FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceMedium
An airplane's positive limit load factor is 3.8G. While cruising at maneuvering speed, the airplane encounters turbulence that produces a momentary gust load factor of 3.5G. What is the most accurate conclusion?
- AThe gust load factor is irrelevant because turbulence loads are not structural loads
- BThe load remained within the airplane's limit load factor, and no structural damage should occur
- CThe airplane exceeded its structural limits and must be inspected for damage
- DThe load exceeded the ultimate load factor, making airframe failure likely
Show answer & explanationAnswer & explanation
Correct answer: B. The load remained within the airplane's limit load factor, and no structural damage should occur
Since 3.5G is less than the airplane's positive limit load factor of 3.8G, the structure remains within its design limits and no permanent deformation or damage should occur. The limit load factor represents the maximum load the structure can sustain without permanent damage, while the ultimate load factor (typically 1.5× limit) is the point of structural failure.
Why the other options are wrong
- A. Turbulence loads are structural loads and must be considered against limit load factor.
- C. 3.5G is below the 3.8G limit, so no exceedance occurred.
- D. Ultimate load factor is typically 1.5× limit load (about 5.7G here), far above 3.5G.
Limit Load Factor
The maximum load factor an aircraft structure can withstand without permanent deformation; loads below this value are considered safe.
- Limit load factor: safe design boundary
- Ultimate load factor ≈ 1.5× limit load factor (failure point)
- Gust loads in turbulence must be compared to limit load factor
Memory trick: Stay under the limit, and the airframe stays legit.