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- Feb 15, 2012
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I have now experienced five times, what seems to be a curious engine shudder, like it missed a beat or two.
It always occurs during the climbout, anywhere from 5000 to 7000 ft, when at full power, in clear sky (although with a moister layer below), at just below freezing temps, but with a carb inlet temp of 15F or so, temp certainly in carb ice territory.
It ONLY occurs the first flight of the day, on subsequent flights (airplane on ground from an hour to two hours), it never occurs.
The engine analyzer shows nothing unusual, but then the event is on the order of 1/2 sec, so it is unlikely to capture it even with a 1 Hz capture frequency. High power mag check is normal.
The first time it occurred, after a usual check over, not finding anything I ignored it and continued. The second time, I aborted the flight, and diverted back to home base. Talked at length with my mechanic, and we did another checkout under the cowl. Plane is out of annual in November, and it is only ten hours since then. Hard to get out with the icing conditions, crazy warm January this year.
Now, it is more just trying to figure it out, I have not engaged in any lengthy flights, have stayed high, and around airports.
Since this started, it has occurred every first flight of the day. It only occurs once on such a flight.
I have applied carb heat each time, but it doesn't fit the pattern for carb ice.
I normally sump, and I have done extra big sumps since this started. No water, no dirt.
It seems to be tied to some sort of operational factor, given how it occurs so consistently, always in the climb, never more than once a flight, and only the first flight of the day.
Is is something other than the engine? I've heard of nose gear flutter causing momentary vibration, but this doesn't seem to fit that pattern.
Any thoughts on this would be welcome.
* Orest
It always occurs during the climbout, anywhere from 5000 to 7000 ft, when at full power, in clear sky (although with a moister layer below), at just below freezing temps, but with a carb inlet temp of 15F or so, temp certainly in carb ice territory.
It ONLY occurs the first flight of the day, on subsequent flights (airplane on ground from an hour to two hours), it never occurs.
The engine analyzer shows nothing unusual, but then the event is on the order of 1/2 sec, so it is unlikely to capture it even with a 1 Hz capture frequency. High power mag check is normal.
The first time it occurred, after a usual check over, not finding anything I ignored it and continued. The second time, I aborted the flight, and diverted back to home base. Talked at length with my mechanic, and we did another checkout under the cowl. Plane is out of annual in November, and it is only ten hours since then. Hard to get out with the icing conditions, crazy warm January this year.
Now, it is more just trying to figure it out, I have not engaged in any lengthy flights, have stayed high, and around airports.
Since this started, it has occurred every first flight of the day. It only occurs once on such a flight.
I have applied carb heat each time, but it doesn't fit the pattern for carb ice.
I normally sump, and I have done extra big sumps since this started. No water, no dirt.
It seems to be tied to some sort of operational factor, given how it occurs so consistently, always in the climb, never more than once a flight, and only the first flight of the day.
Is is something other than the engine? I've heard of nose gear flutter causing momentary vibration, but this doesn't seem to fit that pattern.
Any thoughts on this would be welcome.
* Orest
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