COMPRESSOR SECTION REPAIRS
GENERAL ENGINE REPAIR
AND INSPECTIONS
Most intermediate-level maintenance activities
Before starting disassembly of an engine,
are responsible for the replacement of compressor
sections and the repair of those compressor blades
check the applicable technical instructions to
in the later compressor stages that cannot be
confirm the scope of repair necessary. Use
the step-by-step procedure and repair limits
serviced without the removal of the compressor
halves. Compressor repair usually results from
contained in the current technical publications
for the particular engine. In the process of
foreign object damage (FOD), although other
failures occur. A number of compressor failures
engine disassembly, many associated parts
become accessible for inspection. Inspect these
may be broadly classified under air leaks and
parts as closely as possible to prevent later
compressor contamination. The AIMD may also
failure.
be required to modify the compressor rotor or
stator blades as a result of a technical change or
Support the engine during disassembly and
bulletin. Modifications may include reworking the
buildup to prevent overstressing of the parts being
components, changing blades by stages, or
removed. In addition to preventing stress, it allows
replacing the entire rotor assembly.
proper alignment of parts being removed or
installed.
NOTE: Compressor cases are machined in
matched sets. Damage beyond repair to
Immediately upon removing each subassembly
one case is cause for rejection of the
or individual part from the engine, transfer
opposite case. A new compressor rotor is
it to a parts rack. Arrange the part to protect
not required when replacing the entire case
it or the assembly from damage. Provide proper
assembly.
covering and supports to protect shafts, gears,
studs, or any projecting piece from being bent,
scratched, or otherwise damaged. Be careful to
Compressor Contamination
prevent the entrance of dirt and other foreign
materials into the engine. Whenever practicable,
Accumulation of dirt on the compressor
blades reduces the aerodynamic efficiency of the
use temporary covers to seal all openings in
blades. Dirt hurts engine performance. The
dismantled engines. Cover the ends of all removed
tubing. Take extreme care not to lay carbon
efficiency of the blades is impaired by dirt deposits
seals and plates on the sealing surfaces. Pro-
similar to that of an aircraft wing under icing
vide appropriate containers to hold each part
conditions. High exhaust gas temperature (EGT)
may result when foreign deposits are on
separately until the time for reinstallation.
compressor components. On some turbojet
During disassembly, examine all parts and
assemblies for cracks, scoring, and burning.
engines, high EGT requires early engine overhaul.
Check the engine for indications of work in-
Slow acceleration could also result from foreign
material obstructing the compressor outlet vanes.
correctly performed during any previous repair
This obstruction could result in a needless engine
or overhaul.
overhaul.
You must pay particular attention to the
material requirements for the nuts and bolts used
in the turbojet engine. Hot sections require
Compressor Leaks
common hardware (nuts, bolts, safety wire and
Air leaking from the compressor results in low
cotter pins) that are resistant to high operating
engine performance. Air leakage may occur
temperatures. Other engine parts may require
between the high and low compressors, or at some
special hardware, and it is imperative that all
intermediate stage. It may also occur because of
properly coded parts (if serviceable) be placed in
their original positions.
bleed-air valves stuck open or cracks in the
compressor case itself. Air leaks in the compressor
are found through engine monitoring or low
Welding is permissible on some parts of the
engine performance; for example, when the engine
turbojet engine. Refer to the applicable technical
instructions before attempting to repair an engine
fails to meet minimum power requirements for
or component by welding.
takeoff.
10-5
