Most airplanes feature disc-style brakes similar to those found on automobiles. They are typically found on the main landing gear. Upon touching down, pilots will engage the airplane’s brakes. Heat-resistant discs will then squeeze together to create friction that slows the airplane down. In addition to disc-style brakes such as this, however, many airplanes also feature brake wear pins.
An Introduction to Brake Wear Pins
Brake wear pins are mechanical devices that show how much usable material remains in an airplane’s stators. Stators are essentially brake pads. While brake discs rotate along with wheels, stators remain stationary.
Each time an airplane’s brakes are engaged, stators will lose some of the material from which they are made. Stators are sandwiches between discs. When pilots engage the brakes, the discs will press against the stators. Brake wear pins are designed to show how much stator material remains.
How Airplanes Use Brake Wear Pins
Airplanes use brake wear pins to show how much “life” remains in stators. They consist of rod-like pins that attach to a piston. As the stators wear down, the piston will extend farther out to maintain contact with the discs. Because they are attached to pistons, brake wear pins can reveal how much stator material remains.
The exposed length of a brake wear pin essentially reveals the remaining life of stators. The longer the exposed length, the less life remains. Eventually, brake wear pins will extend far enough out that they indicate the stators have an insufficient amount of material remaining, in which case the stators should be replaced.
Why Airplanes Use Brake Wear Pins
Brake wear pins act as early warning indicators to promote safety. Allowing worn brakes to go unchecked is a serious safety hazard. Statistics show that over half of all airplane accidents occur during landings. With bad brakes, airplanes may fail to stop in time after touching down, resulting in a collision.
Pilots and mechanics use brake wear pins to determine when an airplane’s stators need to be replaced. If the stators are heavily worn, they can be replaced to ensure proper braking function.
While visual cues can often reveal whether the stators need to be replaced, crews can measure brake wear pins for a higher level of precision. Scheduled maintenance, for instance, often includes brake wear pin measurements. Crews will measure the exposed length to determine how much, if any, usable life remains in the stators.
