3.15.
SUMMARY
Gas turbine engines are run in test cells to ensure quality
control before they are shipped to the user for installation in
aircraft. The test cell is equipped with instruments to monitor
engine performance. Engine vibration tests can be performed with the
engine in the test cell or installed in the aircraft. Vibration
tests are required after any maintenance on rotating parts or when
excessive engine vibration is suspected. A jetcal analyzer is used
to check the accuracy of the egt system and to calibrate it.
There are two kinds of engine inspections, scheduled and
special. Scheduled inspections are required whenever any of the
operating limits have been exceeded.
Under the Army Spectrometric Oil Analysis Program (ASOAP) oil
samples are analyzed for metal content, to prevent inflight engine
failures.
Personnel performing maintenance on gas turbine engines should
observe the precautions stated in the engine manual to avoid serious
personnel injury or engine damage. All engine cleaning, both
internal and external, should be performed in accordance with the
appropriate engine manual. In most cases the engine manual
prescribes the approved cleaning procedure to be used. Most engine
parts may be cleaned by the vapor degreasing, solvent immersion, or
vapor blasting methods.
The TBO of a gas turbine engine depends upon such things as
operating environment, mission to be performed, and how will the
engine wear as flight time is built up.
Maintenance function assignments are determined by the
maintenance allocation chart found in the aircraft 20 manual. Three
categories of engine storage are used. The decision as to which
category of storage is to be used depends upon the length of time the
engine will be inactive.
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