Deep stall is a dangerous condition that affects certain aircraft designs, notably those with a T-tail configuration. In these designs, the turbulent wake of a stalled main wing "blanks" the horizontal stabilizer, rendering the elevators ineffective and preventing the aircraft from recovering from the stall. An aircraft is any machine capable of atmospheric flight. ... In aircraft a T-tail is an arrangement of the tail control surfaces with the horizontal surfaces (tailplane and elevators) mounted to the top of the fin, rather than the more common location on the fuselage at the base of the fin. ... Simple Definition: An aircraft in flight is usually not pointed directly into the oncoming airflow. ...
Although effects similar to deep stall had been known to occur on many aircraft designs, the name first came into widespread use after a deep stall caused the prototype BAC 1-11 to crash, killing its crew. This led to changes to the aircraft, including the installation of a stick shaker in order to clearly warn the pilot of the problem before it occurred. Stick shakers are now a part of all commercial airliners. Nevertheless, the problem continues to periodically haunt new designs; in the 1980s a prototype of the latest model of the Canadair Challengerbusiness jet entered deep stall during testing, killing one of the test pilots who was unable to jump from the plane in time. The BAC 1-11, or One-Eleven, was a short-range jet airliner designed by Hunting Aircraft and produced by the British Aircraft Corporation (BAC) after Hunting was merged with several other British aviation firms in 1960. ... A stick shaker is a mechanical device connected to the controls of an airliner (also other types of aircraft such as bizjets) in order to warn the pilots that they are close to stalling the aircraft. ... The Canadair Challenger business jet is a family of mid-sized jets produced by Bombardier Aerospace. ... Business jet (slang, Bizjet) is a term for a jet aircraft, usually of modest size, designed for transporting small groups of business people for commercial reasons at a time convenient to their business needs. ...
Image File history File links Diagram illustrating Deep Stall - created to go with article File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
The accident investigation board conducted an exhaustive investigation of the aerodynamic, stability, and control characteristics of the BAC 111 and concluded that the cause of the accident was an unrecoverable deep-stall phenomenon, which was precipitated by the geometric and aerodynamic characteristics of the configuration.
For example, deepstall was found to be responsible for crashes experienced with the Hawker Siddeley Trident transport.
The fourth stall test was made at an altitude of 11,600 ft in the landing configuration and with the stall warning and recovery systems inoperative.
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