An ATSB research report into stall warning events has given new insights into the way in which Australian pilots respond when flying at the margins of safe flight.
Stall warnings indicate to a flight crew that their aircraft will approach a stall if action is not taken to reduce the aircraft’s angle of attack.
Transport Safety Investigation Regulations require that, if a pilot receives a stall warning, they must report it to the ATSB. There were about 250 stall warnings reported to the ATSB in high-capacity air transport in Australia in the five years between 2008 and 2012.
Stall warnings were found to occur in all flight phases and a range of aircraft configurations...
About 75 per cent of the stall warnings reported to the ATSB were genuine warnings of an approaching stall. In only a minority of cases were system problems reported that resulted in false or spurious stall warnings.
Most stall warnings were associated with stick shaker activations, were momentary in duration, and were associated with thunderstorms, clear air turbulence, sudden wind gusts, or windshear, in both visual and instrument meteorological conditions. As a rate per hours flown, stall warnings were more common in Dash 8, Boeing 767, Boeing 717 and Fokker F100 aircraft, although for the F100, almost all reports were for the aircraft’s stall warning systems activating spuriously. Stall warnings were found to occur in all flight phases and a range of aircraft configurations, not exclusively those related to slow speed, high pitch attitude flight, or flight in poor meteorological conditions.