Left this morning for a trip the Idaho and Washington. Now back home due to a repeated short power loss. Here are the details as best I can remember. I talked to two A&Ps after we got back and nothing jumped out at them. I'll get it to my mechanic on Monday. Any thoughts appreciated.
Momentary engine power loss – Mooney Executive - M20F
Engine – Lycoming IO-360 A1A with Bendix fuel injection.
Symptom is a noticeable decrease in engine power for several seconds then a return to normal accompanied by change in vibration hardly enough to be called an increase. The change is large enough to be noticed by a non-pilot but experienced passenger and very apparent to another pilot.
The only change to instrumentation is an increase in fuel pressure when the power reduces and a decrease when power returns along with a decrease in IAS. Changing the mixture might have an effect on the duration of the power loss. The duration is 5-10 seconds and toward the end of the flight was happening one or more times a minute. Happened often enough that expected TAS was reduced.
No change in MP or EGT (JPI 700, no fuel flow).
Changing the throttle has no effect on the symptoms.
Changing the prop has no effect.
Switching tanks, no effect.
Electric fuel pump no effect.
Mag check in flight is fine.
Checked fuel ‘finger’ screen.
Leak checked on ground with electric fuel pump.
Checked mixture and throttle linkages.
First noticed briefly May 28th in the PM descending into Denver area from west. Checked closely then and test fight could not duplicate. Flew 16 hours after doing commercial training including the day XC and nothing noticed by me or the instructor. Today heading to Idaho the power loss was noticed after climb out to 10,500. Seemed to get worse, aborted trip and returned home.
Momentary engine power loss – Mooney Executive - M20F
Engine – Lycoming IO-360 A1A with Bendix fuel injection.
Symptom is a noticeable decrease in engine power for several seconds then a return to normal accompanied by change in vibration hardly enough to be called an increase. The change is large enough to be noticed by a non-pilot but experienced passenger and very apparent to another pilot.
The only change to instrumentation is an increase in fuel pressure when the power reduces and a decrease when power returns along with a decrease in IAS. Changing the mixture might have an effect on the duration of the power loss. The duration is 5-10 seconds and toward the end of the flight was happening one or more times a minute. Happened often enough that expected TAS was reduced.
No change in MP or EGT (JPI 700, no fuel flow).
Changing the throttle has no effect on the symptoms.
Changing the prop has no effect.
Switching tanks, no effect.
Electric fuel pump no effect.
Mag check in flight is fine.
Checked fuel ‘finger’ screen.
Leak checked on ground with electric fuel pump.
Checked mixture and throttle linkages.
First noticed briefly May 28th in the PM descending into Denver area from west. Checked closely then and test fight could not duplicate. Flew 16 hours after doing commercial training including the day XC and nothing noticed by me or the instructor. Today heading to Idaho the power loss was noticed after climb out to 10,500. Seemed to get worse, aborted trip and returned home.