undercarriage

Undercarriage refers to the assembly of components attached to the underside of a vehicle that support, stabilize, and enable movement. In general, it includes wheels, tires, axles, bogies or track frames, suspension elements, braking systems, and the mechanism that attaches the primary structure to the ground and transmits loads to the chassis. The exact composition varies by vehicle type.

In aviation, the undercarriage is commonly called the landing gear. It consists of main gear and, on many aircraft, a nose gear, each with vertical struts, hydraulic or oleo-pneumatic shock absorbers, wheels or bogies, brakes, and retracting mechanisms. Landing gear supports takeoff and landing loads and provides retractable protection during flight for aerodynamic efficiency. Retraction and extension are typically powered by hydraulics, with redundancy and an emergency extension.

For road vehicles, undercarriage generally refers to the suspension and rolling gear: wheel assemblies, axles, springs or dampers, anti-roll bars, steering linkages, and, in some cases, bogies on heavy vehicles. In rail vehicles, the running gear includes bogies (trucks), wheelsets, axles, bearings, suspension, and braking equipment. For tracked vehicles, the undercarriage includes the track frames, road wheels, return rollers, drive sprockets, idlers, and tensioning systems.

Function and maintenance: the undercarriage transfers the vehicle’s weight to the ground, absorbs shock, provides propulsion and braking, and maintains stability and alignment. Regular inspection for wear, corrosion, leaks, tire or track condition, and hydraulic system integrity is essential for safety and performance.