The brakes are used for slowing, stopping, holding, or steering the airplane. They must (1) develop sufficient force to stop the airplane in a reasonable distance; (2) hold the airplane stationary during engine runups at high power settings; and (3) permit steering of the airplane on the ground. Brakes installed in each main landing wheel of an airplane are actuated independently of each other by the pilot. The right-hand brake is controlled by applying toe pressure to the top portion of the right rudder pedal and the left-hand brake is controlled by pressure applied to the top portion of the left rudder pedal. This provides for simultaneous use of rudder and brakes to control the airplane's direction of movement on the ground. Some airplanes are equipped with a hand lever which, when held in the ON position, operates the individual wheel brake as rudder pressure is applied.
The independent brake system is used on most small airplanes. This type of brake system is termed "independent" because it has its own hydraulic fluid reservoir and is entirely independent of the airplane's main hydraulic system.
Independent brake systems are powered by master cylinders similar to those used in conventional automobile brake systems. The system is composed of a reservoir, two master cylinders, mechanical linkage which connects each master cylinder with its corresponding brake pedal, connecting fluid lines, and a brake assembly in each main landing gear wheel.
Each master cylinder is actuated by toe pressure on its respective pedal. The master cylinder builds up pressure by the movement of a piston inside a sealed, fluid filled cylinder. The resulting hydraulic pressure is transmitted through the fluid line which is connected to the brake assembly in the wheel. This results in the braking action (friction) necessary to stop or slow the wheel.
The brakes may be locked for parking by a ratchet type lock built into the mechanical linkage between the master cylinder and the brake pedal. The brakes are unlocked by application of sufficient pressure on the brake pedals to unload the ratchet.