Stall Speed vs Load Factor
Accelerated stall speed rises with the square root of the load factor.
Formula
Variables
Example
2 g: stall speed × 1.41
How it works
In a turn, pull-up, or any maneuver that increases lift demand, the wing has to support more than the aircraft's weight. Since stall happens when the wing reaches its maximum lift coefficient, needing more lift means the wing must fly at a higher angle of attack and therefore at a higher airspeed before it stalls. Because lift varies with speed squared, the stall speed increases with the square root of the load factor, so doubling the load factor raises stall speed by a factor of about 1.41 rather than 2.
When to use it
Use this when estimating accelerated stall speed during turns, pull-outs, or other maneuvers that increase g-loading. It is especially useful in flight training, performance planning, and accident analysis to see how much faster the aircraft must fly to avoid stalling under load.
Worked example, step by step
Given: 1g stall speed, V_s = 48 kt Load factor, n = 3 Step 1: Use the formula V_{s,n} = V_s\sqrt{n} Step 2: Substitute the values V_{s,3} = 48\sqrt{3} Step 3: Calculate \sqrt{3} \approx 1.732 V_{s,3} \approx 48 \times 1.732 = 83.1 Final answer: The stall speed at 3g is about 83 kt.
Common mistakes to avoid
- Using the load factor directly instead of its square root
- Forgetting that load factor must be at least 1 for this simple accelerated-stall relation
- Mixing up indicated airspeed and true airspeed when applying the formula
Did You Know?
Pulling g raises stall speed by the square root of the load factor — tight turns can stall a fast aircraft.
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