Many factors affect the scope and frequency of aircraft undercarriage overhaul.
The possibility of system malfunction increases with severe operating conditions, such as pilot training and agricultural operations.
Cracks are the foremost area of concern, followed closely by worn, sheared, bent, or broken bolts, and elongated boltholes.
Although these defects occur during normal aircraft usage, adverse operating conditions accelerate the problem.
Improper adjustment or lubrication can also cause malfunctioning, especially in landing gear retraction mechanisms.
Excessive lubrication or the wrong type of lubricant can often be as bad or worse than none at all.
With regard to lubrication, closely follow the manufacturer's service and maintenance instructions.
Inspect grease fittings after applying high pressure lubricant to determine that the spring-loaded ball has reseated.
Failure of the ball to reseat is an indication of an internal failure of the fitting which can result in serious damage to the part being lubricated.
Bearing removal and replacement should be routine.
Hawker 125 executive jet landing gear components.
The following items are susceptible to service difficulties and should be given attention.
Aircraft Shock Absorbers...
Inspect the entire shock-strut for evidence of leaks, cracks, and possible bottoming of the piston, as this condi tion causes overloading of landing gear components and contributes to fatigue cracks.
Check all bolts, boltholes, pins, and bushings for condition, lubrication and proper torque values.
Grease fitting holes (pressure type) are especially vulnerable to cracks and cross-threading damage.
Check all safety wire and other locking devices, especially at the main packing gland nuts.
When assembling shock-struts, use the correct type and number of o-rings, chevron seals, and backup rings.
Use only the correct filler valve core assembly, and follow the manufacturer's instructions when servicing with fluid and air.
Either too much or too little air or oil will affect aircraft handling characteristics during taxi, takeoff, and landing, and can cause structural overloads.
Shock cords and rubber discs deteriorate with age and exposure.
When this type of shock absorber is used, inspect for general condition i.
e.
, cleanliness, stretching, fraying, and broken strands.
These components must be kept free of petroleum products as they accelerate deterioration of the rubber.
Nose Gear Assemblies...
Attention should be given to the steering mechanism and should include items such as: torque-links (scissors), torque-tubes, control rods and rod-end bearings, shimmy dampers, cables, and turning stops.
In addition, check all nose landing gear components, including mud scrapers and slush deflectors, for damage from natural elements.
(a) Towing of some aircraft with the rudder locks installed may cause damage to the nose steering linkage and rudder control sys tem.
Exceeding the steering or towing stops should be followed by a close inspection of the entire nose steering assembly.
A broken steerng stop will allow turning beyond the design Limit, transmitting excessive loads to struc.
tures and to the rudder control system.
It is recommended that the nose steering are limits be indicated on the steering collar or fuselage.
(b) Inspect shimmy dampers for leakage around the piston shaft and at fluid line connections, and for abnormal wear or looseness around the pivot points.
Also check for proper rigging, "bottoming" of the piston in the cylinder, and.
the condition of the external stops on the steering collar.
Bearing removal and replacement should be routine.
Landing Gear Doors...
Inspect gear doors frequently for cracks, deformation, proper rigging, and general condition.
Gear door hinges are especially susceptible to progressive cracking, which can ultimately result in complete failure, allowing the door to move and cause possible jamming of the gear.
This condition could also result in the loss of the door in flight.
In addition, check for proper safetying of the hinge pins and for distorted, sheared, loose, or cracked hinge rivets.
Inspect the wheelwells for improper location or routing of components and related tubing or wiring which could interfere with the travel of the gear door actuating mechanisms.
Micro-Switches...
Inspect micro-switches security of attachment, cleanliness, general condition, and proper operation.
Check assoed wiring for chafing, proper routing, and determine that protective covers are installed on wiring terminals, if required.
Check condition of the rubber dust boots which protect the micro-switch plungers from dirt and corrosion.