| 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