Stick shaker

A stick shaker is a mechanical device to rapidly and noisily vibrate the control yoke (the "stick") of an aircraft to warn the pilot of an imminent stall. A stick shaker is connected to the control column of most civil jet aircraft and large military aircraft.

The stick shaker is a component of the aircraft's stall protection system, which is composed of fuselage or wing-mounted angle of attack sensors that are connected to an avionics computer. The computer receives input from the AOA sensors and a variety of other flight systems. When the data indicate an imminent stall, the computer actuates both the stick shaker and an auditory alert.

The shaker itself is composed of an electric motor connected to a deliberately unbalanced flywheel. When actuated, the shaker induces a forceful, noisy, and entirely unmistakable shaking of the control yoke. This shaking of the control yoke matches the frequency and amplitude of the stick shaking that occurs due to airflow separation in low-speed aircraft as they approach the stall. The stick shaking is intended to act as a backup to the auditory stall alert, in cases where the flight crew may be distracted.

In larger aircraft (especially in T-tailed jets that might be vulnerable to deep stall), some stall protection systems also include a stick pusher system to automatically push forward on the elevator control, thus reducing the aircraft's angle of attack and preventing the stall. Both systems have to be tested and armed before takeoff and remain armed during flight.

The vibration of the stick shaker is often heard on black box recordings of aircraft that entered a stall condition prior to a crash.

Following the crash of American Airlines Flight 191 on May 25, 1979, the FAA issued an airworthiness directive making stick shakers mandatory for both sets of flight controls on DC-10, -10F, -30, -30F and -40 series aircraft.^[1]

References

↑ http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/83D4FF29A77B501C862569F200686555

Patent for Boeing Stall Protection System (with description)

Aircraft components and systems

Airframe structure	Aft pressure bulkhead Cabane strut Canopy Cruciform tail Dope Empennage Fabric covering Fairing Flying wires Former Fuselage Hardpoint Interplane strut Jury strut Leading edge Lift strut Longeron Nacelle Rib Ring tail Spar Stabilizer Stressed skin Strut T-tail Tailplane Trailing edge Triple tail Twin tail Vertical stabilizer V-tail Y-tail Wing root Wing tip Wingbox

Flight controls	Aileron Airbrake Artificial feel Autopilot Canard Centre stick Deceleron Dive brake Electro-hydraulic actuator Elevator Elevon Flaperon Flight control modes Fly-by-wire Gust lock Rudder Servo tab Side-stick Spoiler Spoileron Stabilator Stick pusher Stick shaker Trim tab Wing warping Yaw damper Yoke

Aerodynamic and high-lift devices	Active Aeroelastic Wing Adaptive compliant wing Blown flap Channel wing Dog-tooth Droop Flap Gouge flap Gurney flap Krueger flap Leading edge cuff LEX Slats Slot Stall strips Strake Variable-sweep wing Vortex generator Vortilon Wing fence Winglet

Avionic and flight instrument systems	ACAS Air data computer Airspeed indicator Altimeter Annunciator panel Attitude indicator Compass Course deviation indicator EFIS EICAS Flight data recorder Flight management system Glass cockpit GPS Heading indicator Horizontal situation indicator INS Pitot-static system Radar altimeter TCAS Transponder Turn and slip indicator Vertical Speed Indicator Yaw string

Propulsion controls, devices and fuel systems	Autothrottle Drop tank FADEC Fuel tank Gascolator Inlet cone Intake ramp NACA cowling Self-sealing fuel tank Splitter plate Throttle Thrust lever Thrust reversal Townend ring Wet wing

Landing and arresting gear	Arrestor hook Autobrake Conventional landing gear Drogue parachute Landing gear Landing gear extender Oleo strut Tricycle landing gear Tundra tire

Escape systems	Ejection seat Escape crew capsule

Other systems	Aircraft lavatory Auxiliary power unit Bleed air system Deicing boot Emergency oxygen system Entertainment system Environmental control system Hydraulic system Ice protection system Landing lights Navigation light Passenger service unit Ram air turbine Weeping wing

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