MODULE 1

    Cards (44)

    • Reliable ways to identify parts worn beyond limits is to:
      -          disassemble the engine
      -          thorough inspection
    • Engine manufacturers - provide overhaul instructions with general instructions and specific tolerances to determine airworthiness of each part
    • The basic steps of the overhaul process:
      1.       Receiving inspection
      2.       Disassembly
      3.       Cleaning
      4.       Visual inspection
      5.       Structural inspection
      6.       Dimensional inspection
      7.       Repair and replacement
      8.       Reassembly
      9.       Installation
      10.   Engine testing and run-in
      11.   Preservation and storage
    • Receiving Inspection - determine the general condition of the engine when it is received, provide an inventory of the engine and all its accessories and associated parts
    • Repair Station - should maintain a complete record of all repair operations and inspections performed on each engine or component overhauled
    • Airworthiness Directives – issued by the FAA pertaining to aircraft and engines whenever it appears that certain changes should be made to correct discrepancies or to improve the reliability of the unit
    • Disassembly – a process where a typical aircraft engine follows a sequence specified in the overhaul manual
    • Inspection Record - should show the dimensions of each part measured and all fits and clearances
    • Cleaning – necessary before disassembling and assembling the engine parts
    • two types of cleaning are required when an engine is overhauled:
      1.       degreasing
      2.       decarbonizing
    • Two of the principal methods for removing the residual lubricating oil and loose sludge arc
      -          washing in a petroleum solvent
      -          employment of a vapor degreaser
    • Vapor Degreaser - consists of an enclosed booth in which a degreasing solution such as trichloroethylene is heated until it vaporizes
    • Decarbonizing – next method after the degreasing process has been completed
    • The most common methods of decarbonizing are:
      -          stripping
      -          grit blasting
      -          vapor blasting
    • Stripping – a process is used to remove paint and various resinous varnishes which have formed in the engine during its operation
    • Soft Grit Blasting - offers one of the most satisfactory processes and used for the removal or hard carbon from the insides of cylinders and the tops of pistons
    • Sandblasting – is not employed in the cleaning of engine parts except the valve heads and will erode the metal
    • Vapor blasting - is employed for special cleaning jobs and accomplished by means of specially designed equipment and materials
    • Materials that should not be used for cleaning parts or removing hard carbon:
      -          wire wheels
      -          steel scrapers
      -          putty knives
      -          abrasives
    • Visual Inspection - is accomplished by direct examination and with the use of a magnifying glass
    • Visual inspection - will usually reveal cracks, corrosion, nicks, scratches, galling, scoring and other disturbances of the metal surfaces
    • Structural Inspection - determine the structural integrity of each part
    • Engine parts are structurally inspected by some or all of the following methods:
      1.       Magnetic particle testing
      2.       Liquid penetrant inspection
      3.       Eddy-current inspection
      4.       Ultrasonic inspection
      5.       Radiography
    • Magnetic particle testing - is a nondestructive method for locating surface and subsurface discontinuities (cracks or defect) in ferromagnetic materials such as steel
    • Flux Leakage - occurs where the lines of flux leave the surface or the material. resulting in a concentration of magnetic strength at the discontinuity
    • Liquid Penetrant Inspection - commonly used include crankcase halves. accessory cases. oil sumps, and cylinder heads
    • Ultrasonic Inspection - utilizes high-frequency sound waves to reveal flaws in metal parts
    • Ultrasonic inspection - can be accomplished satisfactorily by a well-trained and experienced TECHNICIAN
    • X-ray Inspection - is particularly effective in detecting discontinuities inside castings, forgings and welds
    • Radiographic Inspection – other term for X-ray Inspection
    • Eddy-current inspection - is also effective in discovering defects inside metal parts
    • Eddy-Current Tester - applies high-frequency electromagnetic waves to the metal and these waves generate eddy currents inside the metal
    • If the metal is uniform in its structure, the eddy currents will flow in a UNIFORM PATTERN and this will be shown by the indicator
    • Eddy-Current Inspection - is not routinely used for engine overhaul.
    • Eddy-Current Tester - can be of great value to a technician who is experienced and knows what type of rests can be made effectively
    • Special Service Bulletins – a bulletin issued by engine manufacturers that require alterations or parts replacements designed to improve the performance and reliability of the engine
    • Dimensional Inspection - requires the use of precision measuring instruments such as micrometer calipers, telescoping gauges, and dial indicators
    • Dimensional inspection - \is employed to determine the degree of wear for parts of the engine where moving surfaces are in contact with other surfaces
    • Manufacturers have designated several parts as recommended or mandatory replacement items at overhaul regardless of their condition. Manufacturer generally agree that these parts should be replaced at overhaul:
      •  Pistons
      •  Piston pins
      •  Piston rings
      •  Main and rod bearings
      • All bushings Connecting-rod bolts and nuts
      • Exhaust valves
    • Repair and Replacement - a process where unrepairable parts and components should have been discarded, repairable parts labeled and parts requiring no further action organized for reassembly on a parts rack. The discrepancy list and labels on repairable parts will serve as a guide for work to be done.
    See similar decks