Airplane Trim Tabs

Posted by Admin on

A trim tab acts in the same relationship as an aileron does to the airfoil, using the change in camber to affect the position of a flight control surface. Figure shows an elevator trim tab, but the same principles apply to rudder or aileron trim tabs.

In this case, the elevator trim is hinged at the trailing edge of the elevator. The trim tab positions may be directly controlled by the pilot to alleviate the need for constant elevator control pressure during various phases of flight, such as in a turn. Trim adjustments will also be necessary as fuel loads and airspeeds change.

Figure depicts both aileron and rudder trim tabs. Most singleengine general-aviation planes are equipped with elevator trim, but a smaller percentage have aileron or rudder trim. Like the elevator trim tabs, aileron and rudder trim cause the control surface to be deflected, alleviating the need for the pilot to maintain constant control pressure. Aileron trim may be useful to eliminate any rolling tendency a plane may exhibit. This could be due to unequal weight distribution, such as more fuel in one wing tank than another, or more passengers on one side of the plane. Sometimes how a plane is rigged, or the twist that is built into the wings, can also result in a rolling tendency. Rudder trim is used to overcome any yawing tendency a plane may have, such as during a climb, when imbalanced propeller thrust may induce a tendency to turn, or when op erating a multiengine aircraft after one engine has failed. Trim, when properly used, goes a long way toward easing a pilot’s workload in the cockpit.

« Prev Post