PHAK Chapter 6-20 Balance Tabs

Balance Tabs

The control forces may be excessively high in some aircraft, and, in order to decrease them, the manufacturer may use balance tabs. 

 

They look like trim tabs and are hinged in approximately the same places as trim tabs. 

 

The essential difference between the two is that the balancing tab is coupled to the control surface rod so that when the primary control surface is moved in any direction, the tab automatically moves in the opposite direction. 

 

The airflow striking the tab counterbalances some of the air pressure against the primary control surface and enables the pilot to move the control more easily and hold the control surface in position. 

 

If the linkage between the balance tab and the fixed surface is adjustable from the flight deck, the tab acts as a combination trim and balance tab that can be adjusted to a desired deflection.

 

Servo Tabs

Servo tabs are very similar in operation and appearance to the trim tabs previously discussed. 

 

A servo tab is a small portion of a flight control surface that deploys in such a way that it helps to move the entire flight control surface in the direction that the pilot wishes it to go. 

 

A servo tab is a dynamic device that deploys to decrease the pilots work load and de-stabilize the aircraft. 

 

Servo tabs are sometimes referred to as flight tabs and are used primarily on large aircraft. 

 

They aid the pilot in moving the control surface and in holding it in the desired position. 

 

Only the servo tab moves in response to movement of the pilot’s flight control, and the force of the airflow on the servo tab then moves the primary control surface. 

 

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