Stalls

A stall occurs when a wing reaches its critical angle of attack. Regardless of load factor, airspeed, bank angle, or atmospheric conditions, a wing always stalls at the same critical angle of attack. Pilots control angle of attack with the elevator.

A stall is an aerodynamic phenomenon—it has nothing to do with an airplane's engine. Gliders, huge airliners, jet fighters, and prop-driven, general aviation trainers all stall when their wings reach a specific angle of attack—not because their engines falter.

Anatomy of a Stall

Up to a point, increasing the angle of attack increases the amount of lift a wing produces. Eventually, however, air flowing over the top of the wing can no longer follow the wing's contour and it begins to swirl like water flowing over rocks in a stream. At this point, called the critical angle of attack, total lift drops suddenly, and the wing stalls.

Every wing has a specific critical angle of attack, and it always stalls at that angle. Most general aviation aircraft have wings with a critical angle of attack of about 15 degrees.

Inexperienced pilots often mistake pitch attitude for angle of attack. Remember that the airplane's flight path (and therefore the relative wind) may not be in the direction that the nose of the airplane is pointing.

Warning Signs

A slight shaking or buffeting often precedes a stall. This vibration begins as the air flowing over the top of the wing becomes turbulent. When this air hits the horizontal stabilizer and elevator you may feel a slight vibration in the control yoke or stick. Most airplanes have a stall warning horn to alert you as the airplane approaches a stall.

Recovering From a Stall