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YO-233-B2A Engine Maintenance Manual
TEO-540-A1A Engine Maintenance Manual
05-50 - TIME LIMITS / MAINTENANCE CHECKS – UNSCHEDULED MAINTENANCE
1. Unusual Conditions
Unscheduled maintenance is necessary when the following conditions occur:
A. Lightning Strike
B. Engine Overspeed
C. Incorrect Fuel or
Fuel Contamination
D. Soaked Engine
A. Lightning Strike
(1) After a lightning strike:
(a) Before next flight, examine the engine and compartment. Look at external surfaces
and internal parts for discoloration, cracks, and other indications of arcing and heat
damage.
NOTICE: Heat from a lightning strike can cause internal damage to the hardened
(b) Complete the Magnaflux and degauss procedure on the steel parts of the engine
during the inspection.
(c) Complete the engine overhaul in accordance with the Direct Drive Overhaul Manual.
Disassemble and examine the engine. Discard all parts that have damage,
discoloration, cracks, etc.
(d) Examine the crankshaft rod journals, main journals, counterweights, camshaft lobes,
bearings, gear teeth, and all other hardened surfaces.
B. Engine Overspeed
(1)
In engine overspeed, the engine operates above its rated (speed) revolutions per minute
(rpm). Momentary overspeed is an increase of no more than 10% of rated engine rpm
for a period not exceeding 3 seconds. If the duration and amount of overspeed is less
than 3 seconds, no further maintenance actions are necessary.
NOTICE: Refer to the engine specifications in the YO-233-B2A Engine Installation and
Operation Manual for rated engine speed.
NOTICE: All incidents of engine overspeed must be recorded in the engine logbook along
with the inspection and any corrective action identified below.
(2)
If any engine is operated at overspeed for more than 3 seconds:
(a)
Identify the category of percent of overspeed based on the three categories of
overspeed shown in Table 1.
(b)
Refer to the latest revision of Service Bulletin No. 369.
© 2021 Avco Corporation. All Rights Reserved
February 2021
E. Engine on Fire or
Near Fire
F. Hydraulic Lock
G. Volcanic Ash/
Particulate
Contamination
surfaces of parts such as ball bearings, crankshaft bearing surfaces, camshaft
lobes, gear teeth, etc.
H. Valve Sticking
I. Oil Starvation/Sudden Loss of Oil Pressure
J. Metal Contamination of the Lubrication
System
K. Propeller Strike, Sudden Engine Stoppage,
or Loss of Propeller Blade Tip
05-50
Page 43
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