Lycoming TEO-540-C1A Maintenance Manual page 237

TEO-540-C1A Engine Maintenance Manual
TEO-540-C1A Engine Maintenance Manual
NOTICE: The orifice size of the differential compression tester is critical for consistent and
meaningful cylinder analysis. A specific orifice size of 0.040 in. diameter (No. 60
drill) x 0.250 in. long, with entrance angle of 59°/60° supplies an acceptable
calibrated leak rate. Larger orifice sizes can decrease the effectiveness of identifying
problems.
(1) All differential compression testers must be in compliance with these specifications:
• 0.250 in. long restrictor orifice
• 0.040 in. ID (No. 61 drill) orifice diameter
• 60° entrance angle
(2) Make sure that all of the gages to be connected to the differential compression tester are
calibrated in accordance with the differential compression tester manufacturer's
specifications.
(3) Refer to the differential compression tester's manufacturer's instructions to ensure the
tester operates correctly.
C. Cylinder Compression Check Procedure
NOTICE: Make sure the differential compression tester has been calibrated and the equipment
check is complete per previous steps before this cylinder compression check.
This check is to be done on an engine installed in the airframe or test stand without
interruption while the cylinder is still warm.
(1) Immediately before the Cylinder Compression Check:
(a) Operate the engine at usual cylinder head and oil temperatures (specified in Appendix
A of the TEO-540-C1A Engine Installation and Operation Manual).
(b) Put the power control in the IDLE CUT-OFF position.
(c) Move the ignition switch to the OFF position to shut down the engine.
© 2018 Avco Corporation. All Rights Reserved
November 2018
Figure 2
Example of a Differential Compression Tester
72-30
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