The AFM/POH for the specific airplane contains information that should be followed in the event of any abnormal engine instrument indications. The table shown in Figure 1 offers generic information on some of the more commonly experienced in-flight abnormal engine instrument indications, their possible causes, and corrective actions.
Malfunction
|
Probable Cause
|
Corrective
Action
|
Loss
of rpm during cruise flight (non-altitude engines)
|
Carburetor
or induction icing or air filter clogging
|
Apply
carburetor heat. If dirty filter is suspected and non-filtered air is
available, switch selector to unfiltered position
|
Loss
of manifold pressure during cruise flight
|
Same
as above
|
Same
as above
|
Turbocharger
failure
|
Possible
exhaust leak. Shut down engine or use lowest practicable power setting. Land
as soon as possible
|
|
Gain
of manifold pressure during cruise flight
|
Throttle
has opened, propeller control has decreased rpm, or improper method of power
reduction
|
Readjust
throttle and tighten friction lock. Reduce manifold pressure prior to
reducing rpm
|
High
oil temperature
|
Oil
congealed in cooler
|
Reduce
power. Land. Preheat engine
|
Inadequate
engine cooling
|
Reduce
power. Increase airspeed
|
|
Detonation
or preignition
|
Observe
cylinder head temperatures for high reading. Reduce manifold pressure. Enrich
mixture
|
|
Forthcoming
internal engine failure
|
Land
as soon as possible or feather propeller and stop engine
|
|
Defective
thermostatic oil cooler control
|
Land
as soon as possible. Consult maintenance personnel
|
|
Low
oil temperature
|
Engine
not warmed up to operating temperature
|
Warm
engine in prescribed manner
|
High
oil pressure
|
Cold
oil
|
Same
as above
|
Possible
internal plugging
|
Reduce
power. Land as soon as possible
|
|
Low
oil pressure
|
Broken
pressure relief valve
|
Land
as soon as possible or feather propeller and stop engine
|
Insufficient
oil
|
Same
as above
|
|
Burned
out bearings
|
Same
as above
|
|
Fluctuating
oil pressure
|
Low
oil supply, loose oil lines, defective pressure relief valve
|
Same
as above
|
High
cylinder head temperature
|
Improper
cowl flap adjustment
|
Adjust
cowl flaps
|
Insufficient
airspeed for cooling
|
Increase
airspeed
|
|
Improper
mixture adjustment
|
Adjust
mixture
|
|
Detonation
or preignition
|
Reduce
power, enrich mixture, increase cooling airflow
|
|
Low cylinder
head temperature
|
Excessive
cowl flap opening
|
Adjust
cowl flaps
|
Excessively
rich mixture
|
Adjust
mixture control
|
|
Extended
glides without clearing engine
|
Clear
engine long enough to keep temperatures at minimum range
|
|
Ammeter
indicating discharge
|
Alternator
or generator failure
|
Shed
unnecessary electrical load. Land as soon as practicable
|
Load
meter indicating zero
|
Same
as above
|
Same
as above
|
Surging
rpm and overspeeding
|
Defective
propeller
|
Adjust
propeller rpm
|
Defective
engine
|
Consult
maintenance
|
|
Defective
propeller governor
|
Adjust
propeller control. Attempt to restore normal operation
|
|
Defective
tachometer
|
Consult
maintenance
|
|
Improper
mixture setting
|
Readjust
mixture for smooth operation
|
|
Loss
of airspeed in cruise flight with manifold pressure and rpm constant
|
Possible
loss of one or more cylinders
|
Land
as soon as possible
|
Rough
running engine
|
Improper
mixture control setting
|
Adjust
mixture for smooth operation
|
Defective
ignition or valves
|
Consult
maintenance personnel
|
|
Detonation
or preignition
|
Reduce
power, enrich mixture, open cowl flaps to reduce cylinder head temp. Land as
soon as practicable
|
|
Induction
air leak
|
Reduce
power. Consult maintenance
|
|
Plugged
fuel nozzle (fuel injection)
|
Same
as above
|
|
Excessive
fuel pressure or fuel flow
|
Lean
mixture control
|
|
Loss
of fuel pressure
|
Engine-driven
pump failure
No
fuel
|
Turn
on boost pumps.
Switch
tanks, turn on fuel
|
Figure 1. Commonly experienced in-flight abnormal engine instrument indications, their possible causes, and corrective actions
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