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A pilot's best friend: The trim wheel

By: Wayne Arbon
Submitted: 2007-06-17 19:29:59
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Are you a pilot and seek the secret to a smooth, easy flight?

If you are forever wrestling with the controls and you have aching arms when you land, you are not using the pilot's best friend - the trim wheel.

Trimming the controls allow a pilot to balance the lift and drag being produced by the wings and control surfaces over a wide range of loads and airspeeds, reducing the effort required to adjust or maintain a desired flight attitude.

A properly-trimmed aircraft can be flown literally with your fingers lightly on the controls. Get into the habit of trimming every time you change attitude or power settings, first letting the aircraft stabilise into the desired attitude.

Use small corrections and take the time to trim correctly – the aircraft will naturally want to stay in equilibrium whether in straight-and-level flight or in a constant ascent or descent.

If you can take your hands off the controls and the aircraft stays in the same attitude, it is trimmed correctly.

The most common example of a trim tab is the elevator trim found in almost all aircraft. The elevator trim tab is adjusted to maintain the angle of attack without pilot interaction.

A properly-trimmed aircraft increases fuel efficiency by reducing drag. A climbing aircraft has a tendency to yaw which increases parasitic drag because more of the fuselage is facing into the wind.

Elevator trim balances the control force necessary to maintain the aerodynamic down force on the tail. Certain flight configurations, such as slow flight, require a lot of trim to maintain the desired angle of attack.

Trimming increases aircraft stability as a properly-trimmed aircraft will return to the same attitude and airspeed after encountering any disturbances such as turbulence or gusts of wind.

There is also trim for the rudder and ailerons used to counter slipstream or the effects of the centre of gravity being to one side.
This can be caused by a larger weight on one side of the aircraft compared to the other, such as when one fuel tank has a more fuel in it than the other or when there are heavier people on one side of the aircraft.

Aileron trim is found mostly on large fixed-wing aircraft.

If the aircraft has a rudder trim wheel, use it - it's a lot easier than flying with one foot on a rudder pedal to centre the ball.

Take the time to learn the skills of correct trimming and you will be surprised at just how easy a properly-trimmed aircraft is to fly.

  Wayne Arbon is a journalist, passionate aviator and editor of Aviation Online.

Article source: Expert Articles