Cleaning

• Properly clean landing gear, including the tires, rims, struts, hydraulic lines, attachment joints and landing gear doors, on a regular basis. Clean the landing gear parts with a neutral solvent solution or a mild dishwashing soap to remove oil, grease, oxidation and dirt. Thorough cleaning allows for easy inspection of all moving parts, making any structural cracks or split seams more visible.
  
  

Tires

• Proper tire pressure and condition should be the number one consideration on the project list. Tires must be filled to the proper PSI (pounds per square inch) required by the manufacture's recommendations. Low aircraft tires can produce wobbling, slow takeoff speeds and excessive bounce or "mushiness" upon landing. Overinflated tires risk the danger of explosion upon heavy landing impact and cause stress on struts and joints during stiff landing. Use a tire gauge to measure tread depth according to manufacture's specification. Worn tire treads allow slippage and poor braking.
  
  

Lubrication

• Inspect all mechanical wear points just after cleaning. Inspect all the mechanical jackscrews, open and close latches, door hinges, cables, pulleys and bell cranks. You must grease such parts to ensure they function smoothly and open or close within their full range of operation. Check for grease points equipped with grease zerk fittings, and lubricate the fittings with a grease gun. Use approved grease of the same brand every time you need to lubricate. Remove old grease from retractable landing gear components, and replace it with fresh grease.
  
  

Wheel Bearings

• Inspect the landing gear wheel bearing by lifting the aircraft up with a landing gear jack and placing it on blocks. Pull the wheel on its vertical axis and from side to side to check for an excess play at the bearing joint. Remove the wheel fastener nuts and pull the wheels off. Remove and clean the bearings in solvent, and check for pitting, galling and wear on the ball or roller bearings. Inspect the bearing races for wear. Replace defective bearings. Repack the wheel bearings with fresh grease.
  
  

Struts and Shocks

• Examine struts for any bends, cracks or misalignment. Fixed landing gear struts have a certain amount of spring or flex in their design, but if stressed too hard they can become damaged. Examine their connection points to the wheel hub and aircraft frame for stress cracks. Tighten up any loose bolts, according to the proper torquing sequence in your service manual. Inspect retractable landing gear struts for alignment and tight-secure hydraulic line couplers. Inspect the tube bodies of retractable landing gear shocks for broken seals and fluid leakage. Change the shock hydraulic fluid at prescribed maintenance internals.
  
  

Vintage Struts

• Older aircraft may come equipped with rubber bungee cord shocks, which have braided sheaths. The braided material should not have any abnormal stretching, thinning or fraying anywhere along its length. Replace any bungee cord shocks with the proper color code with the MIL-C-5651A designated replacement part. Inspect the "spring-oleo" type struts for cracks, burrs, leakage and operational smoothness.
  
  

Retractable Landing Gear

• Inspect the retractable landing gear components for any looseness or excessive play. This includes the trunnion or joints, bearings, hydraulic line fasteners and lines. Support the weight of aircraft on strut jacks and note the operation of the landing gear in the extended and retractable positions. Look for any timing lag or binding in the hydraulic operation. Grease all lubrication points, according to the service manual's intervals.
  
  

Brakes

• Remove the wheel hubs to inspect the brake lining and wheel cylinders. Measure the brake lining for the minimum allowable thickness, and look for abnormal discoloration. Replace worn, contaminated and glazed (burnt) brake lining with the proper replacement parts. Check brake hold-down hardware for proper function and connection points. For hydraulic breaks, examine the wheel cylinders for leakage or binding. Inspect the hydraulic lines from the wheel all the way to the master cylinder. No air or contaminated brake fluid should be in the lines, wheel cylinders or master cylinder.
  
  

Landing Gear Skis

• Examine the landing gear skis for cracks, corrosion and warp. Skis come in metal, wood or fiberglass designs. If equipped with solid mount skis, check the connection points for loose bolts and shims at the frame connection points. Check the shock cord for tautness and wear. The shock cord keeps the ski tips up during landing. The cable check and safety cable cords keep the skis from twisting too far out of their arc during flight; check them for wear and proper alignment. Inspect retractable skis in the same fashion as retractable wheels, but look for proper clearance between wheel and ski height.
  
  

Landing Gear Floats

• Landing gear floats have a tendency to strike objects in the water. Look for dents, cracks and split seams in pontoon floats, whether their construction incorporates wood, metal or fiberglass. A deep crease in metal or wood will indicate a structurally compromised area that could cause flooding. No water should exist inside the floats. Sand down blisters or corrosion spots and examine the condition of the under-surface. Blisters and corrosion will frequently appear on floats used in saltwater. Landing gear floats should be cleaned often with mild soap and water to remove salt, algae and oxidation.