A minimum of preheat application may warm the engine enough to permit starting but will not
de-congeal oil in the sump, lines, cooler, filter, etc. Congealed oil in such lines may require
considerable preheat.
The engine may start and apparently run satisfactorily, but can be
damaged from lack of lubrication due to congealed oil in various parts of the system. The
amount of damage will vary and may not become evident for many hours. On the other hand,
the engine may be severely damaged and could fail shortly following application of high power.
Proper procedures require thorough application of preheat to all parts of the engine. Hot air
should be applied directly to the oil sump and external oil lines as well as the cylinders, air
intake and oil cooler. Excessive hot air can damage nonmetallic components such as seals,
hoses and drive belts, so do not attempt to hasten the preheat process.
Before starting is attempted, turn the engine by hand or starter until it rotates freely.
After starting, observe carefully for high or low oil pressure and continue the warm-up until
the engine operates smoothly and all controls can be moved freely.
Do not close the cowl
flaps to facilitate warm-up, as hot spots may develop and damage ignition wiring and other
components.
2.
Hot air should be applied primarily to the oil sump and filter area. The oil drain
plug door or panel may provide access to these areas. Continue to apply heat for 15 to
30 minutes and turn the propeller, by hand, through
6
or
8
revolutions at 5 to 10 minute
intervals.
3.
Periodically feel the top of the engine, and when some warmth is noted, apply heat
directly to the upper portion of the engine for approximately five minutes.
This will
provide sufficient heating of the cylinders and fuel lines to promote better vaporization
for starting. If enough heater hoses are available, continue heating the sump area.
Otherwise, it will suffice to transfer the source of heat from the sump to the upper part
of the engine.
4.
Start the engine immediately after completion of the preheating process. Since the
engine will be warm, use normal starting procedure.
NOTE.
.
.
Since the oil in the oil pressure gage line may be congealed, as much as 60
seconds may elapse before oil pressure is indicated.
If oil pressure is not indicated
within one minute, shut the engine down and determine the cause.
5.
Operate the engine at 1000
'RPM until some oil temperature is indicated. Monitor
oil pressure closely during the time and be alert for a sudden increase or decrease.
Retard throttle,
if necessary to maintain oil pressure below 100 psi. If oil pressure drops
suddenly to less than
30
psi, shut down the engine and inspect the lubrication system.
If no damage or leaks are noted, preheat the engine for an additional 10 to 15 minutes
before restarting.
6.
Before takeoff, run up the engine to 1700 RPM. If necessary approach this RPM in
increments to prevent oil pressure from exceeding 100 psi.
At 1700 RPM, adjust the propeller control to Full Decrease RPM until minimum governing
RPM is observed, then return the control to Full Increase RPM. Repeat this procedure three
or four times to circulate warm oil into the propeller dome.
If the aircraft manufacturer
recommends checking the propeller feathering system, move the control to the Feather
position, but do not allow the RPM to drop more than 300 RPM below minimum governing
speed.
NOTE.
.
.
Continually monitor oil pressure during run-up.
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