Landing Gear Overhaul
A behind the scenes look at some of the steps involved in this inspection
By Thomas Davis
Photos by Joe Escobar
There is an old adage in aviation: "Take offs are optional and landings are mandatory." Landing gear supports the aircraft at rest and during the landing where the most pressure and stresses are imposed. The shock absorber does what it is designed to do, absorbs the initial shock of the landing and transmits the shock forces in reduced levels to the rest of the landing gear and to the airframe. In order to assure safe operation of the landing gear, most aircraft manufacturers have specific overhaul limits established, as well as life limits imposed on the landing gear assemblies, or on parts within the assembly. The following article is based on some of the procedures used by Dallas, Texas-based TXI Aviation when performing landing gear overhauls.
Components receive NDT inspections as required.
Upon arrival, a visual inspection is conducted for obvious damage and missing parts. A complete inventory of the landing gear assemblies is performed. The customer is notified immediately of any missing or surplus parts. Taking care of missing parts promptly keeps the work on schedule and avoids unnecessary cost to the client. Returning any surplus material to the customer right away is important because many times landing gear work is done in conjunction with other airframe work which might involve these parts.
Once a work order is opened and the Incoming/Outgoing check sheet is begun, the gear is disassembled. The parts are then cleaned and prepared for inspection. Landing gears are subject to rough service and are normally pretty dirty when received for overhaul. Dirt, asphalt, salt deposits, brake dust, grease, and oil, in addition to paint and primer, must be removed. A variety of approved cleaning methods are employed including solvents, steam, soap and other cleaning agents, and blasting. When using media blasting, plastic blast media is used on non-ferrous material such as aluminum and magnesium, and glass blast media is used on ferrous material such as steel. Ferrous and non-ferrous materials and their blast media are kept separated to prevent contamination and dissimilar metal corrosion. Once the parts are clean, they are ready for inspection.
The evaluation process involves inspecting the landing gear per the manufacturer’s overhaul or inspection requirements. The general objective is to inspect the gear for wear, corrosion and damage. Fits and clearances of major parts are measured for wear tolerances. Dimensional inspections are performed using precision measuring equipment and tolerances can be as fine as .0001 inch. When applicable, a geometrical check of the gear’s major parts is performed to assure proper alignment and confirm the landing gear was not bent or overstressed.
Parts that require non-destructive testing (NDT) are sent to the NDT department for the inspections required. Magnetic Particle, Dye Penetrant or Eddy Current inspection of all parts requiring NDT are accomplished. Parts with indications of cracks or defects are noted in the work order for further evaluation, repair or replacement.
During the evaluation phase, FAA life-limited parts, Airworthiness Directives and Manufacturer Service Bulletins are researched to ensure compliance. For maximum reliability, manufacturer service bulletins and other improvements to aircraft landing gear should always be incorporated per the aircraft and component manufacturer’s current instructions. Many of these bulletins are interrelated with each other as well as with the overhaul manuals and aircraft maintenance schedule.
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