SECTION 3
CESSNA
EMERGENCY PROCEDURES
MODEL 172RG
direction of rotation, the symbolic airplane in the turn
coordinator may be referred to for this information.
ROUGH ENGINE OPERATION OR LOSS OF
POWER
CARBURETOR ICING
An unexplained drop in manifold pressure and eventual engine
roughness may result from the formation of carburetor ice. To clear the ice,
apply full throttle and pull the carburetor heat knob full out until the
engine runs smoothly; then remove carburetor heat and readjust the
throttle. If conditions require the continued use of carburetor heat in cruise
flight, use the minimum amount of heat necessary to prevent ice from
forming and lean the mixture for smoothest engine operation.
SPARK PLUG FOULING
A slight engine roughness in flight may be caused by one or more
spark plugs becoming fouled by carbon or lead deposits. This may be
verified by turning the ignition switch momentarily from BOTH to either L
or R position. An obvious power loss in single ignition operation is
evidence of spark plug or magneto trouble. Assuming that spark plugs are
the more likely cause, lean the mixture to the recommended lean setting for
cruising flight. If the problem does not clear up in several minutes,
determine if a richer mixture setting will produce smoother operation. If
not, proceed to the nearest airport for repairs using the BOTH position of
the ignition switch unless extreme roughness dictates the use of a single
ignition position.
MAGNETO MALFUNCTION
A sudden engine roughness or misfiring is usually evidence of
magneto problems. Switching from BOTH to either L or R ignition switch
position will identify which magneto is malfunctioning. Select different
power settings and enrichen the mixture to determine if continued opera-
tion on BOTH magnetos is practicable. If not, switch to the good magneto
and proceed to the nearest airport for repairs.
ENGINE-DRIVEN FUEL PUMP FAILURE
In the event of an engine-driven fuel pump failure, gravity flow will
provide sufficient fuel flow for level or descending flight. However, in a
climbing attitude or anytime the fuel pressure drops to 0.5 PSI, the
auxiliary fuel pump should be turned on.
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1 July 1979
CESSNA
SECTION 3
MODEL 172RG
EMERGENCY PROCEDURES
LOW OIL PRESSURE
If low oil pressure is accompanied by normal oil temperature, there is
a possibility the oil pressure gage or relief valve is malfunctioning. A leak
in the line to the gage is not necessarily cause for an immediate precau-
tionary landing because an orifice in this line will prevent a sudden loss of
oil from the engine sump. However, a landing at the nearest airport would
be advisable to inspect the source of trouble.
If a total loss of oil pressure is accompanied by a rise in oil tempera-
ture, there is good reason to suspect an engine failure is imminent. Reduce
engine power immediately and select a suitable forced landing field. Use
only the minimum power required to reach the desired touchdown spot.
LANDING GEAR MALFUNCTION PROCEDURES
In the event of possible landing gear retraction or extension malfunc-
tions, there are several general checks that should be made prior to
initiating the steps outlined in the following paragraphs.
In analyzing a landing gear malfunction, first check that the master
switch is ON and the LDG GEAR and GEAR PUMP circuit breakers are in;
reset, if necessary. Also, check both landing gear position indicator lights
for operation by "pressing-to-test
"
the light units and rotating them at the
same time to check for open dimming shutters. A burned-out bulb can be
replaced in flight by using the bulb from the remaining gear position
indicator light.
RETRACTION MALFUNCTIONS
If the landing gear fails to retract normally, or an intermittent GEAR
UP indicator light is present, check the indicator light for proper operation
and attempt to recycle the landing gear. Place the landing gear lever in the
GEAR DOWN position. When the GEAR DOWN light illuminates, reposi-
tion the gear lever in the GEAR UP position for another retraction attempt.
If the GEAR UP indicator light still fails to illuminate, the flight may be
continued to an airport having maintenance facilities, if practical. If gear
motor operation is audible after a period of one minute following gear
lever retraction actuation, pull the GEAR PUMP circuit breaker switch to
prevent the electric motor from overheating. In this event, remember to re-
engage the circuit breaker switch just prior to landing. Intermittent gear
motor operation may also be detected by momentary fluctuations of the
ammeter needle.
1 July 1979
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