How The Main Types of Trim Tabs Work?

Trim tabs are a common addition to modern aircraft, coming in the form of small surfaces that are attached to the trailing edge of control surfaces. As a highly beneficial type of component, a trim tab serves to reduce or eliminate the need for the application of a control force in order to counteract aerodynamic forces for keeping an aircraft straight and level. In this blog, we will provide a brief overview of the four main types of trim tabs, allowing you to better understand how they are used and the benefits that they bring.

The trim tab is the most basic type, commonly found on various small single-engine aircraft. Connected to the trailing edge of the elevator, the trim tab may be governed by the pilot with the use of a small control wheel that is located within the cockpit. With the control wheel, an adjustment to the nose up position will result in the tab moving down. Meanwhile, the nose down direction will adjust the tab up. By manipulating the trim tab up and down, it will move into the airstream and deflect the elevator in the opposite direction. This makes it much easier to enact changes without requiring the pilot to overcome aerodynamic forces with their own strength.

The balance tab is another secondary control surface, often being very useful for aircraft that face heavy control loads at high speeds. Balance tabs are fairly similar to trim tabs in their appearance, though they are connected to the control surface linkage. This makes it so that when the control surface itself is moved up and down, the balance tab will move in the opposite direction. While somewhat similar still to the trim tab, this method of operation significantly cuts down on the control load on the yoke, ensuring that the aircraft is easier to control and operate.

The antiservo tab is similar to the balance tab, albeit moving in the opposite direction. This means that when the elevator or stabilator is moved up, the antiservo tab will follow suit in the same direction. While most tabs move in opposite directions for the means of counteracting aerodynamic forces, the antiservo tab actually is a limiter to prevent over-controlling the aircraft. For example, one may not want to over-adjust their pitch mid-flight as it can be very dangerous, thus the antiservo tab prevents such occurrences by increasing the amount of force required for carrying out a control surface change. Such tabs can also protect the airframe and its components from overexertion and stress.

The final major type of secondary tab is the ground adjustable tab, that of which is commonly found on the rudder of many aircraft. True to their name, ground adjustable tabs are secondary control surfaces that may be adjusted while on the ground. To do this, the tab can be bent left or right, often with the help of solid surfaces for an ease of change. As ground adjustable tabs require physical force to be applied to surfaces for more manual changes, it is highly recommended that the operator speaks with a mechanic to ensure that damage does not occur. With the use of a ground adjustable tab, pilots can ensure that their aircraft has more coordination and ability to maintain level flight.

As the various trim tabs of aircraft are crucial for their optimal operations, such surfaces should be regularly inspected and well maintained to ensure their operability. Unlimited Purchasing is a premier parts procurement website, and we are your sourcing solution for the trim tabs, control surface parts, and other various aerospace items that you need for your maintenance endeavors and operations. Peruse over 2 billion new, used, and obsolete items as you see fit, and our team of industry experts are always on standby 24/7x365 to assist you through the purchasing process every step of the way.


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