Maintenance Of Landing Gear

Check the closed end rivet nuts

During inspection and before getting rid of any accumulated dirt, airplane mechanics must closely observe the area being examined while the wingtips are gently rocked up and down. Excessive motion between generally close-fitting landing gear parts may indicate wear, cracks, or improper adjustment. If a crack exists, it will normally be indicated by dirt or metallic particles which have a tendency to outline the fault. Seepage of rust inhibiting oils, used to coat internal surfaces of steel tubes, also helps in the early detection of cracks. In addition, a sooty, oily residue around bolts, closed end rivet nuts, and pins is a good indication of looseness or wear.
 

Qualified technical staff must examine the airplane or landing gear structure surrounding any obvious damage, to make sure that no secondary damage remains undetected. Forces can be transmitted along the affected member to remote areas where subsequent normal loads can cause failure at a later time.
 

Prime locations for cracks on any landing gear are bolts, bolt holes, pins,closed end rivet nuts and welds. The following are typical locations where cracks may develop.
 

Most susceptible areas for bolts are at the radius between the head and the shank, and in the location where the threads join the shank.Cracks mainly occur at the edge of bolt holes on the surface and down inside the bore.The usual types of failure in riveted joints or seams are deformation of the rivet heads and skin cracks originating at the rivets' holes.
 

Cracks and subsequent failures of rod ends often begin at the thread end near the bearing and next to or under the jam nut.Cracks develop mainly along the edge of the weld adjacent to the base metal and along the centerline of the bead.Elongated holes are particularly prevalent in taper-pin holes and bolt holes or at the riveted joints of torque tubes and push-pull rods.
 

When an airplane experiences a hard or overweight landing, the aircraft mechanics ought to perform a particular structural inspection of the aircraft, including the landing gear. Landing gear support trusses ought to be inspected for cracked welds, sheared bolts and closed end rivet nuts, and buckled structures. Wheels and tires ought to be inspected for cracks and cuts, and upper and lower wing surfaces ought to be inspected for wrinkles, deformation, and loose or sheared rivets. If any damage can be found, a detailed inspection is recommended.