Accelerated Stalls

4.accelerated-stalls. Accelerated Stalls

An accelerated stall is a stall that occurs at an airspeed higher than the airplane's normal 1G stall speed because the airplane is subjected to a load factor greater than one. Any maneuver that increases load factor — a steep turn, an abrupt pull-up, or a sudden control input — raises the stall speed proportionally. Because the wing always stalls at the same critical angle of attack (typically around 16–20°), the airplane can be made to stall at any airspeed and any pitch attitude if the pilot exceeds that AOA.

Relationship Between Load Factor and Stall Speed

Stall speed varies with the square root of the load factor:

• Vs(accelerated) = Vs(1G) × √(load factor)

For example, an airplane with a 1G stall speed of 50 knots will stall at:

• 60° bank (2G): 50 × √2 ≈ 71 knots
• 45° bank (1.41G): 50 × √1.41 ≈ 59 knots
• 30° bank (1.15G): 50 × √1.15 ≈ 54 knots

This explains why a steep, level turn can produce a stall well above published Vs1, and why pulling abruptly out of a dive can stall the wing at cruise airspeed.

Purpose of the Maneuver

The FAA requires demonstration of accelerated stalls during commercial and flight instructor training to teach the pilot to:

• Recognize the onset of a stall when maneuvering at airspeeds higher than normal stall speed.
• Understand the relationship between load factor, bank angle, and stall speed.
• Recover promptly using the standard stall recovery, before a secondary stall, spin, or excessive altitude loss occurs.

Entry Procedure

Accelerated stalls are typically performed from a steep level turn or a constant-altitude turning descent. The Airplane Flying Handbook procedure is:

1. Clear the area with clearing turns and complete cockpit checks (mixture, fuel pump, carb heat as appropriate).
2. Establish entry altitude at least 3,000 feet AGL (or the manufacturer's recommended minimum, whichever is higher).
3. Reduce airspeed to no more than the airplane's design maneuvering speed (Va) — and never above Va, since accelerated stalls above Va can exceed structural limits.
4. Establish a coordinated level turn at approximately 45° of bank.
5. While maintaining the bank, smoothly and firmly increase back pressure on the elevator to increase the load factor.
6. Continue the increasing back pressure until the stall occurs — recognized by buffet, stall warning, loss of pitch authority, or an uncommanded nose drop or roll.

The stall will occur at a noticeably higher indicated airspeed than a 1G stall and will often feel more pronounced because the wing is unloading from a higher energy state.

Recovery

Recovery uses the same FAA-recommended sequence as any stall:

• Reduce angle of attack by promptly releasing back pressure (pitch toward, but not below, the horizon). This is the single most important action.
• Level the wings with coordinated aileron and rudder once the AOA is reduced.
• Add power as needed (often full power in trainers) while preventing pitch-up from torque and P-factor.
• Return to coordinated flight and recover to the entry altitude and heading without entering a secondary stall.

Do not attempt to roll the wings level before reducing AOA — at high AOA, aileron deflection on the down-going wing increases its AOA further and can induce a spin. Use rudder to control yaw and prevent the nose from slicing.

Common Errors

• Performing the maneuver above Va, risking structural overload.
• Failing to maintain coordination, leading to a snap roll or incipient spin.
• Using aileron rather than reducing AOA to level the wings.
• Excessive altitude loss during recovery.
• Recovering into a secondary stall by pulling too aggressively after the break.
• Insufficient bank or loading, producing only a 1G stall rather than an accelerated one.

Aerodynamic Takeaway

An accelerated stall is the practical demonstration that stall is a function of angle of attack, not airspeed. Whenever the pilot increases load factor — through bank, pull-up, or turbulence — stall speed rises with it. Recognizing the buffet and reducing AOA immediately is the same response regardless of pitch attitude or airspeed at the moment of the break.