Banjo33
Line Up and Wait
Backstory: about a month ago, my right engine started indicating a surge inflight. MP gauge was steady, but rpm was showing almost a steady/consistent, 200 rpm pulse. I could even feel a slight yaw in the plane as this was happening. I was advised to send the prop governor in for an overhaul (10 years/600 hours since the previous overhaul). The prop shop identified the problem as a high internal leak (24 qts per minute...15 is max allowed), so I ordered a replacement, newly overhauled unit.
Got the newly overhauled prop governor installed today and the mechanic and I did a run up on the engine. Down around 1000 rpm, engine rpm on both engines seem to fluctuate 50-100 rpm. Winds were only about 3 kts, so negligible. I think rpm in that range probably doesn't mean much. However, up around 2000-2200 rpm, the right engine (with the new governor) seems to pulse pretty consistently about 25 rpm (it was nearly 200 rpm on the old prop governor...so it's definitely better now). The left engine at the same rpm pulses periodically about the same amount. Of note, a 2700 rpm check for approx 3 seconds saw the rpm stable.
I'm concerned that I may be a little hypersensitive to the fluctuations and can't recall if a little movement of the needle is normal? I don't see a tolerance listed in the manual and the mechanic isn't sure if this is normal behavior or not either.
The fluctuation is a pretty consistent pulse...imagine a real slow dribble of a basketball equating to about 25 rpm (2-3 widths of the tach needle). A very predictable, pretty consistent rhythm...
I'm wondering how much of it could be caused by the cable itself? If I try to reason my way through the problem, I can almost convince myself that it could be a small internal leak that is masked as the rpm is increased. It seemed that the higher the rpm, the smaller the fluctuation.
I'm beginning to think I should fly it and see how it acts airborne...if I feel yawing (would I even feel 25 rpm?) then I know the governor is acting up (but what would be an allowable fluctuation?). If I don't feel yawing then maybe it's the cable? Any chance over-tightening the control arm could cause it to hunt a little?
Got the newly overhauled prop governor installed today and the mechanic and I did a run up on the engine. Down around 1000 rpm, engine rpm on both engines seem to fluctuate 50-100 rpm. Winds were only about 3 kts, so negligible. I think rpm in that range probably doesn't mean much. However, up around 2000-2200 rpm, the right engine (with the new governor) seems to pulse pretty consistently about 25 rpm (it was nearly 200 rpm on the old prop governor...so it's definitely better now). The left engine at the same rpm pulses periodically about the same amount. Of note, a 2700 rpm check for approx 3 seconds saw the rpm stable.
I'm concerned that I may be a little hypersensitive to the fluctuations and can't recall if a little movement of the needle is normal? I don't see a tolerance listed in the manual and the mechanic isn't sure if this is normal behavior or not either.
The fluctuation is a pretty consistent pulse...imagine a real slow dribble of a basketball equating to about 25 rpm (2-3 widths of the tach needle). A very predictable, pretty consistent rhythm...
I'm wondering how much of it could be caused by the cable itself? If I try to reason my way through the problem, I can almost convince myself that it could be a small internal leak that is masked as the rpm is increased. It seemed that the higher the rpm, the smaller the fluctuation.
I'm beginning to think I should fly it and see how it acts airborne...if I feel yawing (would I even feel 25 rpm?) then I know the governor is acting up (but what would be an allowable fluctuation?). If I don't feel yawing then maybe it's the cable? Any chance over-tightening the control arm could cause it to hunt a little?
