Angle of Attack

SAFETY SPOTLIGHT: Maneuvering Flight

Stalls and Spins

The FAA eliminated spin demonstrations by most pilot applicants in 1949, leaving only the CFI certificate with that requirement. The rationale for eliminating spins was that emphasis on stall recognition and recovery would provide more benefit than skill in spin recovery. Following the U.S. lead, Canada and the United Kingdom dropped spin demonstrations for non-CFI check rides for the same reasons.

Although the total number of stall/spin accidents has dropped dramatically since 1949, those that do occur usually start at low altitudes. An ASI study of 465 fatal stall/spin accidents that occurred from 1991 through 2000 showed that at least 80 percent of the accidents started from an altitude of less than 1,000 feet agl, the usual traffic pattern altitude. The study found that only 7.1 percent of the aircraft involved in the stall/spin accidents definitely started the stall/spin from an altitude of greater than 1,000 feet agl. Just over 13 percent of the aircraft were reported at an “unknown” altitude at the beginning of the accident, and so were given the benefit of the doubt.

Pilot operating handbooks for various typical GA aircraft estimate average altitude loss during stalls, assuming proper recovery technique, between 100 and 350 feet.

Recovery from a spin is a far different matter, and takes much more altitude, even with skilled pilots. Several NASA studies have shown that the average altitude loss in spins is close to 1,200 feet. So it’s safe to say that a spin at or below traffic pattern altitude will not be recoverable before encountering terrain.

Relative Wind and Angle of Attack

During flight training, we learn that the relative wind is opposite the direction of flight. That is not to be confused with the direction the aircraft’s nose is pointing (the relative wind is often not directly off the nose). Any discussion of relative wind includes angle of attack (AOA)—the angle between the chord line of the wing and the relative wind. When the aircraft exceeds its critical angle of attack, it will stall—for many GA aircraft, that occurs between 16 and 18 degrees, both in nose-up and nose-down flight attitudes, turns, and during pull-ups (vertical turns).

A too-high AOA and subsequent stall can easily happen with the nose down and plenty of airspeed. It’s the AOA, not the airspeed that causes the stall. The chance of an angle-of-attack accident is higher during buzzing, although that type of maneuver can hardly be considered normal flight.

For example, attempting to buzz an object on the ground, you’d descend nose-down, and then—hopefully—pull out of the dive in time to recover. If the angle of attack is too steep during that pull-out, the wing will stall—violently. It won’t be the garden variety stall with minor altitude loss that you experienced in training. At low altitude, the outcome will likely be tragic.

Stall and Spin Accidents: Keep the Wings Flying

While aerobatic training can help with unusual attitude recovery, anyone who believes that it will enable recovery from an inadvertent spin in the traffic pattern is fooling themselves. The AOPA Air Safety Institute Stall and Spin Accidents: Keep the Wings Flying study explores causes and misconceptions about stalls and spins in GA aircraft. The report also recommends improvements in stall recognition training.

Read the report

A too-high AOA and subsequent stall can easily happen with the nose down and plenty of airspeed. It’s the AOA, not the airspeed that causes the stall.

Margins of Safety: Angle of Attack Indicators

Angle of attack indicators warn when you’re about to exceed a wing’s lift capacity. See how AOA indicators work.