Definition
The landing gear of an aircraft, including the wheels, struts, shock absorbers, brakes, and supporting structure that bears the weight of the aircraft on the ground and absorbs the loads of taxi, takeoff, and landing.
Plain English
The wheels and legs an aircraft sits, rolls, and lands on, along with the parts that hold them to the airframe and cushion the impact of touchdown.
Context Anchor
Seen in preflight inspection, maintenance, and landing-gear discussions; in many aviation contexts, undercarriage means the same general system as landing gear.
Derivation
From 'under' (beneath) and 'carriage' (a wheeled structure that carries a load). The term came from horse-drawn vehicles, where the undercarriage was the wheeled framework beneath the body. It transferred naturally to aircraft, where the same idea applies — the structure underneath that carries the weight on wheels.
Why Pilots Care
The undercarriage must function correctly for safe ground handling, takeoff, and landing; damage or malfunction can lead to runway excursions or structural failure.
Intuition Check
Undercarriage does not mean the aircraft’s belly or lower skin. In aviation, it means the support equipment underneath the aircraft, usually called the landing gear.
Example Sentence 1
After a firm landing, the pilot taxied clear of the runway and asked maintenance to inspect the undercarriage for damage.
Example Sentence 2
A soft-field landing technique helps protect the undercarriage when operating on rough grass surfaces.