SECTION 4
CESSNA
NORMAL PROCEDURES
MODEL 172RG
Figure 4-2. Taxiing Diagram
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1 July 1979
CESSNA
SECTION 4
MODEL 172RG
NORMAL PROCEDURES
operation. When the knob is pulled out to the heat position, air entering the
engine is not filtered.
Taxiing over loose gravel or cinders should be done at low engine
speed to avoid abrasion and stone damage to the propeller tips.
BEFORE TAKEOFF
WARM-UP
Since the engine is closely cowled for efficient in-flight cooling,
precautions should be taken to avoid overheating on the ground. Full
power checks on the ground are not recommended unless the pilot has good
reason to suspect that the engine is not turning up properly.
MAGNETO CHECK
The magneto check should be made at 1800 RPM as follows. Move
ignition switch first to R position and note RPM. Next move switch back to
BOTH to clear the other set of plugs. Then move switch to the L position,
note RPM and return the switch to the BOTH position. RPM drop should not
exceed 150 RPM on either magneto or show greater than 50 RPM differen-
tial 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.
An absence of RPM drop may be an indication of faulty grounding of
one side of the ignition system or should be cause for suspicion that the
magneto timing is set in advance of the setting specified.
ALTERNATOR CHECK
Prior to flights where verification of proper alternator and alternator
control unit operation is essential (such as night or instrument flights), a
positive verification can be made by loading the electrical system
momentarily (3 to 5 seconds) with the landing lights during the engine
runup (1700 RPM). The ammeter will remain within a needle width of the
initial reading if the alternator and alternator control unit are operating
properly.
TAKEOFF
POWER CHECK
It is important to check takeoff power early in the takeoff run. Any sign
of rough engine operation or sluggish engine acceleration is good cause
for discontinuing the takeoff.
1 July 1979
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