Cylinder Borescope Inspection - Lycoming TEO-540-C1A Maintenance Manual

5. Cylinder Borescope Inspection

WARNING DURING A CYLINDER BORESCOPE INSPECTION, MAKE SURE THAT
THE IGNITION SWITCH IS TURNED OFF AND THAT POWER TO THE
ENGINE IS DISCONNECTED.
AS A PRECAUTION, DO NOT STAND OR ALLOW ANYONE TO STAND
WITHIN THE ROTATIONAL ARC RADIUS OF THE PROPELLER. MAKE
SURE THE ENGINE IS COOL.
A. The cylinder borescope inspection is done to examine the inner walls of the engine cylinders
for rust, deposits and unusual wear patterns of the combustion chamber, valve, piston top,
and the cylinder barrel without removing the engine cylinder.
B. When to complete the Cylinder Borescope Inspection:
(1) Repeatedly high oil consumption is excessive
(2) 400-hour inspection
(3) After an engine overspeed
(4) Low cylinder compression
(5) If valve sticking is suspected (refer to the "Corrective Action for Valve Sticking" section
in this chapter)
(6) Worn piston rings or worn cylinder barrel
(7) Insufficient combustion
C. Cylinder Borescope Inspection Procedure
(1) Remove a top spark plug from each cylinder per the "Spark Plug Removal" procedure in
Chapter 74-20.
(2) Put the piston at bottom dead center on the power stroke.
(3) Install the borescope through the vacant top spark plug hole on the engine cylinder and
examine the combustion chamber, the top of the piston, the internal surfaces of each
cylinder, including the exhaust valve and exhaust valve seat. Complete inspection steps in
Table 3.
(4) Remove the borescope from the cylinder.
(5) Put the piston at bottom dead center at the end of the intake stroke.
(6) Install the borescope through the vacant spark plug hole and examine the intake valve and
intake valve seat. Complete inspection steps in Table 3. Unless otherwise shown,
corrective action in Table 3 applies to procedures in this chapter.
(7) Reinstall the spark plug in the cylinder per the "Spark Plug Installation" procedure in
Chapter 74-20.
(8) Record all results and corrective action in the 400-Hour Engine Inspection Checklist in
Chapter 05-20 or the engine logbook.
72-30
Page 212
TEO-540-C1A Engine Maintenance Manual
TEO-540-C1A Engine Maintenance Manual
© 2018 Avco Corporation. All Rights Reserved
November 2018