difference between rudder YAW and rudder TRIM
DIFFERENCE between rudder YAW and rudder TRIM?—By Matt
When you hold down the rudder pedal with your foot, are you adjusting rudder yaw or rudder trim? Thanks.
Best Answer—By Ben Dere Dun Dat
Yaw. The rudder pedals operate the rudder which in turn causes the aircraft to yaw to the left or right about the vertical axis of rotation
In a turn, you use rudder to counteract “adverse yaw”, which is the tendancy of the nose to move opposite the direction of the bank due to unequal angle of attack (and therefore unequal lift and drag) of the wings during a turn. If you don’t counteract adverse yaw with rudder the aircraft inefficiently slips sideways through the air, which among other things diminishes your speed and makes the passengers uncomfortable.
Rudder trim, on the other hand is set to hold the rudder in a particular position without needing to use your feet so much to help the aircraft track straight during climb, cruise and descent. Some aircraft have a ground adjustable trim tab on the rudder while others have an adjustable trim tab that is operated by a control in the cockpit. A cockpit adjustable trim tab can be reset for all phases of flight. A ground adjustable trim tab is usually set to help the plane track straight during normal cruise only. With the ground adjustable trim tab, or no tab at all, you have to compensate with rudder inputs for the tendancy of the aircraft to go left during a climb and right during a descent.
I suppose you might argue that the small amount of rudder input required with a fixed tab / no tab setup is in effect trimming the rudder using the rudder pedals, but by convention it is more proper to say that you are preventing yaw instead.
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Comment by
captsead0nkey on 10 May 2009:
The use of rudder counter acts the yaw produced during turns and high angle of attack flight due to left turning tendency. When doing climbs and turns, the use of the rudder keeps the aircraft in coordinated flight.
Rudder trim is just that, trim where it it used to reduce the amount of pressure at the pedal. It is typcially used in multiengine aircraft when doing single engine flight to help hold counter act the yaw produced by the drag of the stopped engine, and the asymetric thrust of the working engine.
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Comment by
James on 10 May 2009:
The rudder pedals control the rudder, which *primarily* controls the yaw of the aircraft (direction about it's yaw axis, AKA it's vertical axis).
Rudder trim is controlled by a tab on the trailing edge of the rudder, which when adjusted “holds” the rudder in a desired position (which could be right or left of center) by aerodynamic forces acting on the trim tab. The purpose of this is to relieve the pilot of needing to apply constant foot pressure to one rudder pedal or the other for a long period of time.
The trim tab, as described by Ben Dere, is either mounted to the rudder on a hinge and is controlled by a trim control in the cockpit, or it is fixed to the rudder without a hinge as a bendable piece of metal that can only be contolled by bending the metal by hand when the aircraft is on the ground.
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