Stall speed at 4 Gs

Remote Pilot (Part 107) practice question 16 of 25 on Loading and Performance. ACS element UA.IV.A.K1 · difficulty: applied. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONAn aircraft has a normal unaccelerated stalling speed of 50 knots. If a load factor of 4 Gs is induced, at what airspeed can it be stalled?

A200 knots (50 × 4)
B100 knots
C71 knots (50 × √2)

Show the answer and explanation

Correct answer: B. 100 knots

A — incorrect Multiplying by the load factor itself is wrong; stall speed rises with the square root of the load factor.
B — correct Stalling speed increases in proportion to the square root of the load factor; the square root of 4 is 2, so 50 knots becomes 100 knots, the example the guide gives.
C — incorrect Using the square root of 2 would correspond to a load factor of 2, not 4.

BACKGROUND

Any aircraft, within the limits of its structure, may be stalled at any airspeed by imposing a sufficiently high angle of attack. The Remote Pilot study guide explains that an aircraft's stalling speed increases in proportion to the square root of the load factor. Its example is an aircraft with a normal unaccelerated stalling speed of 50 knots that can be stalled at 100 knots by inducing a load factor of 4 Gs, and at 150 knots if it could withstand 9 Gs. Pilots should be aware of the danger of inadvertently stalling by increasing the load factor in a steep turn or spiral.

STUDY TIP

Take the square root of the load factor and multiply it by the normal stall speed.

KEY POINTS

Stall speed rises with the square root of the load factor.
50 knots at 4 Gs becomes 100 knots.
Steep turns and abrupt pull-ups can stall an aircraft at seemingly safe speeds.

SOURCES

remote_pilot_study_guide.txt ch4 "Load Factors and Stalling Speeds"

Practice the Remote Pilot (Part 107) test →Timed 60-question exam, by ACS area, or review your misses. Free.