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Aircraft Maintenance Technology
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Landing Gear Maintenance 'Best Practices'
Vulnerability here can increase overhaul costs|
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By James Careless
AMT Contributor
Landing gear: At first glance, it appears to be the most rugged part of an aircraft. But landing gear’s apparent robustness masks its vulnerability to corrosion and stress damage due to impacts — a vulnerability that can result in a substantially reduced operational lifespan (well below manufacturers’ specs) and increased overhaul costs.
What can an aircraft technician do to keep landing gear in top condition between scheduled overhauls? According to Goodrich’s Landing Gear Division in Burlington, Ontario, quite a lot.
Understanding the life of landing gear
The life of an average aircraft’s landing gear is a hard one. At all times, its pressurized oleo-pneumatic shock-absorbers exert stress on their metal housings. Meanwhile, the force of hitting the runway upon landing stresses the entire system, no matter how gentle the landing. Horizontal forces are also exerted on the gear as the aircraft brakes during landing or accelerates during takeoff.
That’s not all. Towing strains the forward landing gear, especially if the tow is not executed gracefully. Add impacts and collisions with other objects on the tarmac, and landing gear can be bent, cracked, and even collapsed due to aircraft accidents.
In the hangar, “landing gear can be damaged by inappropriate jacking and other forms of mishandling,” says Jay Lind, Goodrich Landing Gear Quality Assurance manager. “Even pressure washing the gear to make it look spotless can cause problems, because it can force water into the bushings and joints, causing corrosion.”
If this isn’t enough to worry about, certain solvents such as paint stripper can cause ‘hydrogen embrittlement’ in gear. What happens is that atomic hydrogen found in such substances interacts chemically with the high tensile steel in the gear, causing the affected areas to transform chemically into a brittle alloy with a risk of fracturing. “The only way to counteract hydrogen embrittlement is to remove the affected component and bake it in a special oven at 375 F for 23 hours,” Lind tells AMT. “This allows the hydrogen atoms to migrate to the surface and then escape.”
Maintenance best practices
When damaged aircraft landing gear comes into the shop, it costs more to overhaul than landing gear that has been maintained properly. Here is what you can do to keep your landing gear costs down.
