FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightMedium
An airplane's unaccelerated, wings-level stall speed is 60 knots. During a steep turn at a 60° bank angle, maintaining altitude, the load factor is 2 G. What is the approximate accelerated stall speed in this turn?
- A170 knots
- B120 knots
- C85 knots
- D60 knots
Show answer & explanationAnswer & explanation
Correct answer: C. 85 knots
Accelerated stall speed increases with the square root of the load factor: Vs(accel) = Vs × √n = 60 × √2 = 60 × 1.414 ≈ 85 knots. This is why steep turns significantly raise the stall speed even though weight has not changed.
Why the other options are wrong
- A. Overestimates; this would need a load factor near 8.
- B. Would require a load factor of 4, not 2.
- D. Ignores the load factor increase entirely.
Accelerated Stall Speed Formula
Stall speed in a turn increases with the square root of the load factor: Vs(accel) = Vs(unaccel) × √n.
- 60° bank level turn produces 2 G load factor
- Stall speed increases by factor of √n, not n
- Steeper turns dramatically raise stall speed and risk of accelerated stall
Memory trick: Square root the G's to find the new stall speed