Servo Brake

A servo brake is a type of aircraft wheel brake system that uses mechanical or hydraulic assistance to increase the braking force applied. When the pilot presses the brake pedal, hydraulic pressure pushes brake shoes (which have high-friction lining material) against a brake drum—a hollow cylinder connected to the wheel. Because the brake drum rotates as the aircraft moves, this rotation causes the brake shoes to wedge themselves more tightly against the drum, increasing friction automatically. This means the faster the aircraft is moving, the stronger the braking force becomes without requiring the pilot to apply extra effort. In simple terms, the servo brake helps the pilot apply brakes more easily while improving the effectiveness of the braking system overall.
This type of brake is still used in older aircraft and some light aircraft.