Aircraft what is trim

There are several different types of trim systems in use and more than one type may be found on a given aircraft. The most commonly used trim system is the trim tab which can be installed in both fixed or flight adjustable configurations.

Adjustable springs, anti-servo tabs on a stabilator equipped aircraft and a trimmable horizontal stabiliser are other types of trim systems.

The torque is the "twisting force" that produces the rotation. To trim the aircraft it is necessary to balance the torques produced by the wing and the tail. The torque from the wing is equal to the lift of the wing W times the distance from the cg to the center of pressure of the wing dw. The torque from the tail is equal to the lift of the tail T times the distance from the cg to the center of pressure of the tail dt.

If the distances are both positive same side of the center of gravity , then the direction of the tail force must be different than the direction of the wing force to produce no net torque or rotation.

However, if the distance to the tail were negative, then the lift of the of the tail could be positive and there would be no net torque.

A negative distance to the tail would imply that the tail is on the front of the aircraft, ahead of the center of gravity. A tail at the front of the aircraft is called a canard and was the configuration first used by the Wright brothers.

The total lift of the aircraft is the vector sum of the wing lift and the tail lift. For the airliner, the total lift is less than the wing lift; for the Wright brothers, the total lift is greater than the wing lift. The added lift was important for the Wright brothers because their aircraft had a very small engine and flew at low speeds 35mph. Since lift depends on the square of the velocity , it is hard to generate enough lift for flight at such low speeds.

For this reason you may see aileron trim tabs on only one aileron or sometimes they will be on both if the aircraft was designed that way. Even in single installations, the aileron trim still affects both wings simultaneously. Aileron trim can be used whenever the aircraft will not maintain straight flight. Sometimes airplanes can develop slight roll tendencies to one side or the other for a number of reasons minor dents, stretching and re-rigging of the control surface cables, change of onboard equipment and will require slight but perpetual aileron trim to correct it.

The larger need for aileron trim comes from the weight and balance of the aircraft passenger, crew, and fuel loading and configuration. The need for aileron trim could also change during the course of the flight as fuel is burned off and the weight and balance of the aircraft changes.

A safe and accurate way to trim an aircraft elevator, rudder, or aileron is to achieve the desired flight attitude with the yoke or stick and then slowly trim the aircraft until the yoke pressure is no longer needed to maintain the same attitude.

In other words, set the airplane in the desired attitude and then use trim to hold the airplane in that attitude where your input is no longer required. It is important to not use the trim adjustment wheel, crank handle or other device to force the airplane to fly as you want.

Critically, the order of application for all movable trims such as this is to use the pilots own effort to get the aircraft in the correct yaw, pitch and bank attitude, then use the trim to relieve the trim pressures required, checking and adjusting always in this same order.

The proficient and consistent use of aircraft trim is a useful and often necessary tool for all pilots, and especially for those pilots who fly at night, in heavy traffic areas such as Class C or B airspaces or in IMC where pilot workloads can quickly become overwhelming.

Aircraft trim is designed to ease that workload while also adding to the efficient, safe and fun operation of your aircraft. I've been flying since I was 14 years old and have loved every minute of pursuing aviation ever since.

Particular highlights include my seaplane rating in Talkeetna Alaska in a Super Cub on floats, getting my instrument rating, taking mountain flying courses in the Idaho backcountry, and purchasing my first airplane a Cessna P in Aviation is my biggest passion and Airplane Academy is my outlet to continually research aviation tips, tricks, and FAQs and present them in a helpful way both on this website as well as our YouTube channel.

You can read more about my story here. I recently had a phone call and email exchange with an air traffic controller named Mike, who has worked in several different ATC roles in the San Antonio, Texas region. He is currently an approach Nearly all of the topics I most commonly get asked about flight training, all in one place, for free. Skip to content Pilots often have a lot to do when flying and aircraft trim helps pilots manage that workload and keep the aircraft moving in the right direction.