SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/comm-stall-speed-4g

An airplane stalls at 50 knots in level flight. At what speed could a 4 G pull-up stall it?

100 knots, because stall speed grows with the square root of load factor.

Start playing free

  1. 70 knots
  2. 200 knots
  3. 100 knots ✔

Why: Stall speed rises with the square root of the load factor. The square root of 4 is 2, so 50 knots doubles to 100 knots. A hard pull-up can stall you at a speed that looks safe.

Huh, didn't know that: Handbook example: a 45-knot airplane in a bank steeper than 72 degrees must stay above 75 knots to avoid a stall.

The dad joke
Why did the airplane need a cheat sheet? It kept getting stalled on the square root question.
Like this card?
Play the game

References

Answer: 100 knots. Stall speed rises with the square root of the load factor. The square root of 4 is 2, so 50 knots doubles to 100 knots. A hard pull-up can stall you at a speed that looks safe.

  1. PHAK ch 5, Aerodynamics of Flight (FAA-H-8083-25C) www.faa.gov/sites/faa.gov/files/07_phak_ch5_0.pdf
    a normal unaccelerated stalling speed of 50 knots can be stalled at 100 knots by inducing a load factor of 4 Gs.
    Checked 2026-10-10.
  2. PHAK ch 5, Aerodynamics of Flight (FAA-H-8083-25C) www.faa.gov/sites/faa.gov/files/07_phak_ch5_0.pdf
    the airspeed must be kept greater than 75 knots to prevent inducing a stall
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

FlyingA coordinated, level turn at 60 degrees of bank puts how much load factor on the airplane?FlyingHow does moving the CG forward change an airplane's stall speed?FlyingWhat can a commercial pilot do that a private pilot generally cannot?

That's stuff everyone should know.