Specifications

CESSNA SECTION 4
MODEL 172R NAV III NORMAL PROCEDURES
GFC 700 AFCS
U.S.
BEFORE TAKEOFF
WARM UP
If the engine idles, with the throttle against the idle stop, (approximately
600 RPM) and accelerates smoothly, the engine is warm enough for
takeoff. Since the engine is closely cowled for efficient in-flight engine
cooling, the airplane should be pointed into the wind to avoid
overheating during prolonged engine operation on the ground. Long
periods of idling may cause fouled spark plugs.
MAGNETO CHECK
The magneto check must be made at 1800 RPM. Turn the
MAGNETOS switch from the BOTH position to the R position. Note the
new RPM, then turn the MAGNETOS switch back to the BOTH position
to clear the spark plugs. Turn the MAGNETOS switch to the L position,
note the new RPM, then turn the switch back to the BOTH position.
RPM decrease should not be more than 150 RPM on either magneto or
be greater than 50 RPM differential between magnetos. If there is a
doubt concerning operation of the ignition system, RPM checks at
higher engine speeds will usually confirm whether a deficiency exists.
No RPM drop may indicate a faulty ground to one magneto or magneto
timing set in advance of the angle specified.
ALTERNATOR CHECK
Make sure that both the alternator and alternator control unit are
operating properly before night or instrument flight, or flights where
electrical power is essential. Check the electrical system during the
MAGNETO check (1800 RPM) by setting all electrical equipment
required for the flight to the ON position. When the alternator and
alternator control unit are both operating properly, the ammeters will
show zero or positive current (amps), the voltmeters should show
between 27 to 29 volts, and no electrical system annunciations will
appear. Reduce the electrical load before reducing engine speed so the
battery will not discharge while the engine is at idle.
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172RPHBUS-00 4-29