A fixed-wing small unmanned aircraft has a normal unaccelerated stalling speed of 30 knots. During a steep turn, the load factor reaches 4 Gs. At about what airspeed could the aircraft now stall?
- A30 knots, because load factor does not change the stalling speed
- B60 knots
- C120 knots
Show answer and explanation
Correct answer: B. 60 knots
Per the study guide, stalling speed increases in proportion to the square root of the load factor. Its example: a 50-knot stalling speed becomes 100 knots at 4 Gs. With a 30-knot stalling speed and a 4 G load factor, the aircraft can stall at about 30 × 2 = 60 knots.
- A. Incorrect. The study guide states that an increased load factor increases the stalling speed and makes stalls possible at seemingly safe flight speeds.
- B. Correct. Stalling speed increases in proportion to the square root of the load factor. The square root of 4 is 2, so 30 knots × 2 = 60 knots.
- C. Incorrect. This multiplies the stalling speed by the full load factor. Stalling speed increases with the square root of the load factor, not the load factor itself.
FAA-G-8082-22 Remote Pilot – sUAS Study Guide, Chapter 4, Load Factors and Stalling Speeds, p. 31 A study of this effect has revealed that an aircraft’s stalling speed increases in proportion to the square root of the load factor. This means that an aircraft with a normal unaccelerated stalling speed of 50 knots can be stalled at 100 knots by inducing a load factor of 4 Gs.
FAA-G-8082-22 Remote Pilot – sUAS Study Guide, Chapter 4, Load Factors, p. 30 2. An increased load factor increases the stalling speed and makes stalls possible at seemingly safe flight speeds.