From the Shop Floor: Landing Gear
operational problems.
By Brad Crudup
In this edition of our regular "From the Shop Floor" column, Brad Crudup, chief of maintenance at Global Aviation Services in Houston, offers some preflight advice concerning the landing gear.
A quick but thorough preflight inspection of the main landing gear and nose gear should help to prevent unforeseen problems from developing in those all-important components. Begin by examining the main landing gear clamshell gear door actuating cylinders. Make sure the shaft from each actuating cylinder is screwed tightly into the gear door rod end. The shaft can work loose over time, preventing the gear doors from seating properly when closed.
Check the chrome portion of the main landing gear struts for grease, dirt, and other contaminants that can erode the strut seal. Wipe any contaminants clean using a rag dampened with 5606 hydraulic fluid. This will help keep the strut seals in good shape.
Make sure the strut on each main landing gear is extended an equal length. It's difficult to say what the correct strut length should be because it differs with each airplane. However, too-little extension (an under-inflated strut) could cause the scissors to catch on the engine nacelle structure and prevent the gear from fully retracting or extending.
Examine the bushings on the main gear scissor at the protruding "knee." Any visible gaps in the bushings is an indication of wear that can affect the toe-in/toe-out alignment of the main gear tire and lead to premature wear of the tire.
Make sure the main landing gear bungees are not frayed, and that the thickness of each bungee is consistent all the way around. If a portion of one or more bungees is thinner in diameter, it could be a sign that the bands that make up the bungee are beginning to break, causing the remaining bands to stretch.
Check the wheels and brakes for signs of leaking fluid or dampness. Long taxis can cause the brakes to overheat, which can affect brake seals. Any dampness around brake components can be a sign of deteriorating seals that could soon fail.
Make sure the tires are properly inflated with nitrogen. This should be done weekly. Incorrect tire pressure, especially under inflation, leads to abnormal tire wear.
Be sure to look the nose gear over closely as well. Check the steering collar for signs of black, soot-like deposits, which is an indication of wear. Check the strut for proper extension and contaminants, and clean as described earlier. Finally, check tire pressure weekly, and service with nitrogen.
The landing gear may be out of sight and out of mind when you're flying, but you won't get very far on the ground without it. Treat it well.
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