Features

January 2010 Issue

Deep Stall Aerodynamics

You didn’t practice this type of stall during your primary flight training. They’re generally unrecoverable, and mainly affect swept-wing jets.

In October 22, 1963, a prototype of the British Aircraft Corporation One-Eleven (BAC 1-11) short-haul jet airliner, registration G-ASHG, crashed near the village of Chicklade in southwest England. The aircraft was evaluating stall characteristics at varying center of gravity locations when the flight crew found the flight controls unresponsive after entering a stable stall and the aircraft struck the ground at a wings level attitude with a high rate of descent and little forward speed. All aboard died in the crash. The 1-11 was one of the second-generation of jet airliners—others being the Douglas DC-9 and Boeing 727—featuring aft-mounted engines, swept wings and all-moving T-tail horizontal stabilizers. Post-crash investigation concluded the prototype 1-11 had experienced an unrecoverable deep stall in which the wake of the stalled wing covered the high-mounted horizontal stabilizer, thus blanking the elevator controls and preventing normal recovery techniques.

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