Shock absorbers absorb landing energy and protect the structure from peak loads.
Three common designs
| Type | Operation | Examples |
|---|---|---|
| Spring-steel mains | Steel leaf-spring flexes under load and rebounds — simple, low maintenance | Cessna 152, 172 (standard mains) |
| Bungee cord | Elastic rubber cords cushion the gear to the fuselage | Piper Cub, older Champions |
| Oleo-pneumatic (oil-pressure) | Hydraulic fluid + compressed nitrogen/air in a strut — best damping characteristic | Retractable gear (PA-28R, Bonanza, all larger types) |
Oleo-pneumatic strut — how it works
| Phase | Behaviour |
|---|---|
| Impact (landing) | Hydraulic fluid flows through an orifice, absorbing kinetic energy as heat |
| Rebound | Nitrogen/air pressure extends the strut |
| Static | Nitrogen pressure holds the aircraft at the correct standing height |
The correct standing height (strut inflation) is specified in the AFM — usually as "X inches of strut exposed". If too low: refill the strut (nitrogen, by a maintenance technician).
Pre-flight visual check
- Main gear standing height — even, AFM-compliant
- Nose gear shock — no oil leak, correct standing height
- Steel spring (Cessna) — no cracks or deformation
- Bungee (where applicable) — no visible cracks or fraying