Go-around at 250 ft that becomes an accelerated-stall situation
You are flying a Cessna 172 on a visual approach with 30° of flap at 65 KIAS. At about 250 ft agl the tower instructs you to go around because the aircraft ahead has not cleared the runway. You apply full power, but before the flaps have moved the aircraft drifts left of the extended centreline towards a line of trees on that side. You roll into a 60° bank to turn back, holding 20° of flap, and the airspeed is now 58 KIAS. The stall warning sounds. Aircraft weight is about 2,200 lb. From the POH, at this weight the stall speed is 48 KIAS clean and 44 KIAS with 20° of flap; Vx is 62 KIAS, Vy is 74 KIAS and Va is 105 KIAS.
1. Calculate the load factor in the 60° bank and the accelerated stall speed with 20° of flap, and explain why the horn sounded at 58 KIAS.
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Load factor. In a level, coordinated turn n = 1 / cos(bank angle). At 60°, cos 60° = 0.5, so n = 1 / 0.5 = 2.0 g.
Accelerated stall speed. Stall speed rises with the square root of load factor: Vs(acc) = Vs × √n = 44 × √2 = 44 × 1.414 ≈ 62 KIAS.
Why the horn sounded. At 58 KIAS the aircraft was already 4 kt below its stalling speed for that combination of bank and flap, so the wing was stalled or on the point of it - the horn is a warning that arrives before the stall, and here it arrived when the margin had already gone. Nothing was wrong with the wing; the pilot had simply demanded twice the lift that level flight requires at a speed that could not supply it.
Note also that the stall was not caused by the bank alone. The bank raised the required lift, and the low speed and the flaps set the available lift. At 60° of bank, the aircraft needed about 62 KIAS to stay flying and had 58.
2. The pilot's instinct is to retract the remaining 20° of flap while rolling out. Evaluate that instinct in this specific situation.
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It is the wrong first move, and it is the move most likely to turn a warning into an accident.
Flap retraction raises the stalling speed. Clean, the stall speed is 48 KIAS, not 44. At 60° of bank that means an accelerated stall speed of 48 × 1.414 ≈ 68 KIAS - higher than the speed at which the aircraft was already warning. For the several seconds it takes to accelerate, the margin would get worse, not better.
Flap retraction also causes an immediate loss of lift and a sink. At 250 ft agl with trees ahead, a sink of even 100 ft is significant, and the pitch change can provoke the pilot into pulling, which loads the wing further.
The correct first action is to reduce bank. Load factor falls fast with bank angle: at 45° it is 1.41 (accelerated stall with 20° flap ≈ 52 KIAS); at 30° it is 1.15 (≈ 47 KIAS); at 20° it is 1.06 (≈ 45 KIAS). Unloading the wing by rolling out buys the margin that retracting flap would remove.
Flap should be retracted only after the aircraft is accelerating in level flight or a shallow climb, and in stages.
3. Write out the sequence of actions you would fly from the moment the horn sounds, including target speeds and altitudes.
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- Roll out of the bank immediately, to 30° or less, without pulling. Accept the drift towards the extended centreline's edge rather than trading altitude for tracking - trees are the hazard, not the centreline.
- Hold the nose attitude that gives about 62–65 KIAS. Do not chase airspeed by pulling; lower the nose if the horn continues.
- Confirm full power, carburettor heat cold, mixture rich, and check that the engine has actually delivered the power you asked for.
- At a safe altitude, with 65 KIAS or more and a positive rate of climb, retract flap from 20° to 10°, then to 0° once above about 65 KIAS again. Each selection should be small and unhurried.
- Once clean and above Vx (62 KIAS), establish a climb at Vy (74 KIAS) and turn back to the centreline only when above 500 ft agl.
- Tell the tower what happened and take the spacing you need for the next approach.
All manoeuvring stays below Va (105 KIAS), and full abrupt control travel is avoided until well clear of the ground.