Flight Study: Abnormal Engine Instrument Indication

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
Loss of manifold pressure during cruise flight	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
High oil pressure	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

In-Flight Fire

Flight Control Malfunction/Failure

Systems Malfunctions

Door Opening In-Flight

Inadvertent VFR Flight Into IMC

Abnormal Engine Instrument Indication - Airplane Emergency Procedure