Page 283 - The Jet Engine

Overhaul

Fig. 25-12 Torque tightening.

53. During assembling, inspection checks are Testing
made. These checks can establish dimensions to 55. On completion of assembly, every production
enable axial and radial clearances to be calculated and/or overhauled engine must be tested in a 'sea-
and adjustments to be made, or they can ascertain level' test cell (fig. 25-14), i.e. a test cell in which the
that vital fitting operations have been correctly engine is run at ambient temperature and pressure
effected. Dimensional checks are effected during conditions, the resultant performance figures being
disassembly to establish datums which must be corrected to International Standard Atmosphere
repeated on subsequent re-assernbly. (I.S.A.) sea-level conditions (Part 21).
56. To ensure that the engine performance meets
54. To ensure that the nuts, bolts and setscrews
throughout the engine and its accessories are that guaranteed to the customer and the require-
ments of the Government licensing and purchasing
uniformly tight, controlled torque tightening is authorities, each engine is tested to an acceptance
applied, fig. 25-12, the torque loading figure is test schedule.
determined by the thread diameter and the differing
coefficients of friction allied with thread finish i.e., 57. In addition to the 'sea-level' tests, sample
silver or cadmium plating and the lubricant used. engines are tested to a flight evaluation test

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