Warm-Up; Magneto Check; Alternator Check; Takeoff - Cessna SKYHAWK 172M 1976 Pilot Operating Handbook

CESSNA
MODEL 172M
SECTION 4
NORMAL PROCEDURES
,Pilled 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
If
the engine accelerates smoothly, the airplane is ready for takeoff.
Since the engine is closely cowled for efficient in-flight engine cooling,
precautions should be taken to avoid overheating during prolonged engine
operation on the ground. Also, long periods of idling may cause fouled
spark plugs.
MAGNETO CHECK
The magneto check should be made at 1700 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 posi-
tion, note RPM and return the switch to the BOTH position. RPM drop
should not exceed 125 RPM on either magneto or show greater than 50
RPM differential between magnetos.
If
there is a doubt concerning opera-
tion of the ignition system, RPM checks at higher engine speeds will usu-
ally 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 voltage
regulator operation is essential (such as night or instrument flights), a
positive verification can be made by loading the electrical system momen-
tarily (3 to 5 seconds) with the optional landing light (if so equipped), or
by operating the wing flaps during the engine runup (1700 RPM). The am-
meter will remain within a needle width of zero
if
the alternator and vol-
tage regulator are operating properly.
TAKEOFF
POWER CHECK
It is important to check full-throttle engine operati.on early in the
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