Stick pusher

Lore & Background

In October 1963, a BAC One-Eleven airliner crashed during a stall test when pilots pushed the T-tailed plane past stall recovery limits into a deep stall, where disturbed air from the stalled wing rendered the elevator ineffective. As a consequence, a combined stick shaker/pusher system was installed in all production One-Eleven airliners. Following the crash of American Airlines Flight 191 on 25 May 1979, the FAA issued an airworthiness directive mandating stick shakers on both sets of flight controls on most models of the McDonnell Douglas DC-10. The traditional stick pusher arrangement was established by Boeing, though Boeing historically avoided integrating stick pushers on many aircraft as a matter of flying philosophy to avoid overly-automating actions. Among other aircraft, the 300 Series of the De Havilland Canada Dash 8 was equipped with this system.

There are several variations among stick pushers. Textron Aviation developed its own arrangement for the Citation Longitude, automating the pusher system via integration with the computerized autopilot, eliminating electro-mechanical mechanisms and using the autopilot servo to push the nose down. A similar arrangement was adopted on the Pilatus PC-24. Bombardier Aviation incorporated a stick pusher onto its Challenger 600 family. Lockheed Martin included a stick pusher in the new generation C-130J Super Hercules after unexpected stall characteristics delayed entry into service and could not be resolved via aerodynamic alterations. The Embraer ERJ family was equipped with a stick pusher despite completing all stall tests without incident. In Europe, airliners not known for deep-stall characteristics, such as the McDonnell Douglas MD-80, were routinely required to be outfitted with stick pushers even where other regulatory bodies found such devices unnecessary.

The principle of the stick pusher is also applicable to rotorcraft, with collective pull down devices functioning similarly. A stick pusher should not be confused with a stick shaker, which warns pilots of an imminent stall through rapid vibrations of the control yoke. To unfamiliar flight crew, activation of the stick pusher can feel abrupt, vigorous, and alarming, but this is intended to ensure it takes effect before a serious stall sets in. Aircraft designers recognize the risk of erroneous activation and must make provisions for flight crew to address unwanted activation; in some aircraft, the stick pusher can be overpowered or manually disabled by the pilot.

Reader's Guide

The stick pusher's significance lies in its role as a safety device that automatically reduces angle of attack to prevent stalls, particularly in aircraft with poor post-stall handling or deep stall vulnerability. The article notes that safety requirements for transport-category and many military aircraft are demanding in pre-stall handling and stall recovery, and some aircraft cannot comply relying solely on natural aerodynamic qualities. The device constantly monitors critical parameters—angle of attack, airspeed, wing flap setting, and load factor—and activates without pilot action. Its legacy includes regulatory mandates: after the 1963 BAC One-Eleven crash, a combined stick shaker/pusher system was installed in production models, and a new design requirement emerged allowing a stick pusher as an alternative for compliance. The 1979 American Airlines Flight 191 crash led to an FAA airworthiness directive for stick shakers on DC-10s. During the 2000s, a series of accidents were attributed to improper crew responses to stick pusher activation, prompting the FAA in the early 2010s to issue guidance urging proper training. The device's abrupt activation is intentional, and designers must account for potential erroneous activation, with provisions for pilots to overpower or disable the system.

Did You Know?

• The stick pusher was installed on all production BAC One-Eleven airliners after a 1963 crash during a stall test.
• The FAA mandated stick shakers on both sets of flight controls on most McDonnell Douglas DC-10 models after the 1979 crash of American Airlines Flight 191.
• Textron Aviation's Citation Longitude uses the autopilot servo to push the nose down, eliminating electro-mechanical mechanisms.
• The stick pusher principle also applies to rotorcraft via collective pull down devices, typically as aftermarket additions.