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Showing results for tags 'engine surging while leaning'.
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Bravo engine surging while leaning at cruise power
Rick Junkin posted a topic in Mooney Bravo Owners
Greetings all, I'm looking for information about engine surging at cruise power while leaning to cruise fuel flow, and resolutions to this issue that others may have discovered. I promised my wife I'd start with this - "Riddle me THIS, Batman..." I've encountered this on my last two flight attempts, after having convinced myself that I induced the anomaly on the first sortie with too rapid throttle/mixture adjustments. Flight conditions for the first sortie were 15,500 MSL at the top of the climb out, 34/2400 and 24.5gph (leaned slightly) set on the climb. After leveling off and reaching cruise speed, I set 30/2200 and began leaning fairly quickly to get to about 16gph, but the engine began surging well before then. It caught me by surprise, so I didn't catch all of the parameters during the fluctuations as I enriched the mixture to stop the surging. I tried leaning again with the same results, this time MP looked to be cycling between 30"and about 20", and I'm guessing that RPM was between 2200 and about 1000, based on sound as I didn't see the numbers. Unfortunately I don't have the instrumentation on board to capture the exact numbers. The surging stopped when I went full rich on the mixture and I left it there for an uneventful RTB. I did a run up post flight, and everything was normal. I convinced myself that I had induced this anomaly due to leaning in the climb (first time I had tried that technique) and percolated the fuel with higher than normal temps (1550TIT, CHTs 370-390), leading to a surge condition. On the second sortie (today), I was very deliberate in my adjustments and encountered the same anomaly. Today's flight conditions were 6,500 MSL at 30"/2200RPM, leaning from a cruise climb fuel flow of 25-26gph (full rich) at 34"/2400RPM. Leveled at 6,500MSL with 30/2200 set, I was leaning at a rate of about one full twist of the mixture control every 5 seconds. Leaning through 18.3gph the engine began to surge. I started enriching the mixture at the bottom of the second surge cycle and the surging stopped, so I then went full rich and I left it there for an uneventful RTB. Again, I did a normal run up check on the ground and everything was normal. I then did a high power run up to replicate the inflight engine parameters of 30"/2200, and leaned all the way through RPM decay with no surging. The peak TIT/CHT during the ground run was 1610/376. I also ran my prop through a complete min/max cycle at 2000RPM to hopefully rule out a prop governor issue, with no anomalies noted. Up to this point I have set cruise power and leaned to find peak TIT usually between 15gph and 14gph, and enriched 100DF. I've never had any surging. With the CND ground run results, I'm at a loss for what to look at. Could it be that one of the controllers is having issues? Or perhaps the mixture controller? It only happens inflight... Thanks for any insight you may have, I'm meeting a Mooney expert mechanic at the airplane tomorrow morning to take a look and will report back with our findings. Cheers, Rick- 43 replies
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- cruise power engine surging
- engine surging
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