Definition
The component of a disc brake assembly that straddles the brake disc and houses the hydraulic pistons and brake linings (pads). When hydraulic pressure is applied, the caliper's pistons squeeze the linings against both faces of the rotating disc, producing the friction that slows or stops the wheel.
Plain English
The clamp-like part of a disc brake that presses brake pads against a spinning disc on the wheel to slow it down. Hydraulic fluid pushes pistons inside the caliper, which push the pads against the disc.
Context Anchor
Seen during landing gear inspection, wheel and brake maintenance, and preflight checks around the aircraft wheels.
Derivation
Caliper comes from the older word 'calipers,' a measuring tool with two arms that grip an object from both sides. The brake caliper is named for the same reason — it grips the brake disc from both sides.
Why Pilots Care
A properly functioning brake caliper ensures the aircraft can stop within required runway distances and prevents brake fade or failure.
Intuition Check
Do not think of a brake caliper as just a measuring tool. On an aircraft brake, it is the clamp-like part that applies braking force to the disc.
Example Sentence 1
During the preflight walk-around, the pilot checked each brake caliper for hydraulic fluid leaks and uneven lining wear.
Example Sentence 2
The mechanic replaced the worn brake caliper after noticing reduced stopping performance on landing.