When maintaining or repairing an airliner, having a clear understanding of its suspension system is crucial. The suspension parts list for an airliner includes components that handle landing loads, taxiing, and ground maneuvers. This guide breaks down the essential parts, their functions, and practical considerations for sourcing replacements.
Main Components of an Airliner Suspension System
The suspension system of an airliner is primarily the landing gear assembly, which absorbs impact during landing and supports the aircraft on the ground. The following subsections detail the core parts found on most commercial jets.
Landing Gear Legs and Struts
The main structural members are the landing gear legs (or struts). On a typical airliner, you have two main gear legs attached to the wing structure and a nose gear leg. These legs are thick metal cylinders, often made of high-strength steel or titanium alloys, designed to handle static weight and dynamic landing forces. Each leg contains an inner piston that slides within an outer cylinder to compress during landing. The parts list always includes the leg assembly, including the outer cylinder, inner piston, and associated seals.
Shock Absorbers (Oleo Struts)
The oleo-pneumatic shock absorber, commonly called an oleo strut, is the heart of the suspension. It uses hydraulic oil and compressed nitrogen to dampen oscillations. Key parts within the oleo strut include the metering pin, orifice plate, packing glands, and gas charging valve. The metering pin controls oil flow during compression and extension, providing a smooth ride. Maintenance technicians often need replacement seals, O-rings, and gas valves as part of a suspension parts kit.
Torque Links
Torque links are hinged arms connecting the upper and lower parts of the landing gear leg. They prevent rotation of the lower strut relative to the upper cylinder, ensuring the wheels stay aligned. On a parts list, torque links appear as matched sets with bushings and bolts. Worn torque link bushings can cause steering slop and uneven tire wear, so they are common replacement items.
Axles and Wheels
The axle is the shaft on which the wheel assembly rotates. Airliner axles are hollow to save weight and are often made of heat-treated steel. The wheel itself consists of a hub, bearing cups, and brake disc mounts. The parts list for the wheel includes bearings, races, wheel halves (for split wheels), and fasteners. Tires are not strictly suspension parts, but they work closely with the suspension system.
Brakes and Anti-Skid
Brake assemblies are mounted on the wheel and include carbon or steel brake discs, pistons, and heat shields. The anti-skid system uses sensors to prevent wheel lockup, and its components include wheel speed transducers and control valves. While brakes are not part of the springing function, they are integral to the overall landing gear parts list.
Secondary Suspension Parts
Beyond the primary load-bearing components, several supporting parts are essential for proper function.
Hydraulic Actuators
Many airliners use hydraulic actuators to retract and extend the landing gear. These actuators are powerful cylinders that move the gear into the wheel well. They include seals, piston rods, and mounting brackets. On a parts list, hydraulic actuators are often listed as assemblies or with specific overhaul kits containing seals and bearings.
Steering Components
The nose landing gear typically has a steering system that allows the pilot to control the aircraft on the ground. Parts include steering actuators, tillers, centering cams, and dampers. The centering cam helps align the nose wheels straight when the gear is retracted. A common part request is the steering damper, which prevents shimmy.
Safety Pins and Locks
During maintenance, safety pins are inserted to prevent accidental gear retraction. The lock mechanism includes up-locks and down-locks that physically hold the gear in position. These are critical safety items and should always be inspected per the maintenance manual.
Materials and Construction
Airliner suspension parts are built from materials that must withstand extreme loads, temperature variations, and corrosion. Common materials include:
- High-strength steel (e.g., 4340 alloy) for structural struts
- Aluminum alloys for lighter components like hydraulic actuators (where stresses are lower)
- Titanium for high-stress, weight-critical parts
- Chrome plating on sliding surfaces for wear resistance
- Elastomeric seals (Viton, Buna-N) for fluid retention
When sourcing parts, always verify material certifications (e.g., FAA PMA or original equipment manufacturer specs) to ensure compliance with airworthiness standards.
Maintenance and Replacement Considerations
Even with robust design, suspension parts wear over time. Common issues include seal leaks, bushing wear, and corrosion. A typical suspension parts list for a C-check might include:
- Oleo seal kit
- Torque link bushings
- Axle bearings
- Hydraulic actuator seal kit
- Brake disc set
Technicians should follow the Aircraft Maintenance Manual (AMM) for replacement intervals. Always use proper corrosion-inhibiting coatings when installing parts.
Final Recommendation: Sourcing Suspension Parts
When building or restocking an airliner suspension parts list, prioritize genuine or FAA-approved parts. Work with established aviation suppliers like Aviall, Boeing Distribution, or local overhaul shops. Always cross-reference part numbers with the manufacturer's IPC (Illustrated Parts Catalog). For common parts like seals and bushings, having a stock kit on hand can reduce aircraft downtime.
Remember, every part on an airliner's suspension is safety-critical. Proper identification, sourcing, and installation are non-negotiable. Use this list as a starting point for understanding what goes into an airliner's ground handling system.