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 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. Shutdown 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 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 pressure, 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 soon as possible |
| Rough running engine | Improper mixture control setting | Adjust mixture for smooth operation |
| Defective ignition or valve | Consult maintenance personnel | |
| Detonation or preignition | Reduce power, enrich mixture, open cowl flaps to reduce cylinder head temp. Land as soon as possible | |
| 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 |
Commonly experienced in-flight abnormal engine instrument indications, their possible causes, and corrective actions