FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightEasy
A student pilot asks why an airplane's indicated stall speed changes with weight and bank angle, yet the instructor insists the airplane always stalls at the same angle of attack. The instructor's statement is correct because:
- AAngle of attack decreases as weight increases, delaying the stall
- BHeavier airplanes stall at a lower angle of attack to compensate for the added weight
- CCritical angle of attack is a fixed aerodynamic characteristic of a given wing regardless of weight, bank, or airspeed
- DStall speed is only affected by air density, not by angle of attack
Show answer & explanationAnswer & explanation
Correct answer: C. Critical angle of attack is a fixed aerodynamic characteristic of a given wing regardless of weight, bank, or airspeed
For any given wing/flap configuration, the critical angle of attack at which the airflow separates and the wing stalls is constant. Changes in weight, bank, or load factor change the airspeed at which that critical angle is reached, not the angle itself.
Why the other options are wrong
- A. Reverses the relationship — AOA required for level flight increases with weight, not decreases.
- B. Incorrect; critical AOA does not vary with weight.
- D. Density affects true airspeed relationships but not the AOA at which stall occurs.
Critical AOA is Constant
A given wing always stalls at the same critical angle of attack regardless of weight, airspeed, or bank angle; only the indicated airspeed at stall changes.
- Critical AOA fixed by wing design and configuration
- Stall speed varies with weight/load factor, not AOA
- Flaps change the critical AOA value for that configuration
Memory trick: Same angle, different speed — stall doesn't care about weight