How does the stick shaker work?

Question

Large aircraft have a feature that shakes the control stick/wheel before the onset of a stall.   How does this gadget know that a stall is imminent?  Is it monitoring actual wing loading or airflow or something... or is it just indicating a theoretical imminent stall based on airspeed, angle of attack and other flight parameters?

For instance if the wings had taken damage which increased their stall speed... would the shaker know this?

Erik T · Accepted Answer

In the Cessna Citation, the stick shaker is linked to the air data sensor and takes the airspeed and the angle of attack and determines when the aircraft is about to stall and starts to vibrate and shake.  It is also accompanied by an alarm.  When that happens it's time to break the stall and power out of it.

If the wings were damaged, it wouldn't know that, however the angle of attack might increase and the stall might occur sooner than normal, but the stick shaker would still do it's job.  Depends on the damage.

ZKSUJ · Answer

Usually linked to an Angle of Attack indicator on the outside of an aircraft. This indicator is a vane (Usually) into the airflow which is linked to the computers onboard. It measures the Aircraft's Angle of Attack (The angle between the chord line and Relative Airflow of the wing). Seeing as the aircraft stall is related to the angle of attack and not so much the speed, the indicator will sense the aircraft has surpassed a predetermined angle of attack, in which case the computer will signal the stick shaker to activate.

Hope this makes sense

BioHazard · Answer

Planes with stick shakers will also have angle of attack (AOA) sensors, and yes, they work in conjunction with airspeed and other computer data to predict a stall rather than monitoring airflow for an actual stall. And no, the system wouldn't know about damage affecting flight characteristics

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How does the stick shaker work?

3 Answers