gevertex Posted March 11 Report Posted March 11 Hey all, I've noticed some RPM surges on initial climb recently. Roughly 50 RPM change indicated accompanied by a brief change in engine pitch. My governor was overhauled just a couple years ago. Savvy said no signs of other issues like misfires, etc. Wanted to see what the hive mind thought. Quote
M20F Posted March 13 Report Posted March 13 Your top graph which it appears to me that the greenline is RPM does not show a 50 RPM change? Quote
gevertex Posted Thursday at 08:47 PM Author Report Posted Thursday at 08:47 PM 5 hours ago, M20F said: Your top graph which it appears to me that the greenline is RPM does not show a 50 RPM change? Correct, green line. Here are the numbers for reference. This is enough to hear a pitch change and sometimes feel a change in power. Also this only happens at high RPM. Once I reduce to 2400 for cruise, I have never noticed a change (except when leaning). Quote
PeteMc Posted Thursday at 09:22 PM Report Posted Thursday at 09:22 PM Do you hear or feel it, or just see it on the instruments? Quote
gevertex Posted Thursday at 09:32 PM Author Report Posted Thursday at 09:32 PM 8 minutes ago, PeteMc said: Do you hear or feel it, or just see it on the instruments? Can definitely hear it. I felt it the last time it happened as well. The sky was extremely smooth that day. Quote
dkkim73 Posted Thursday at 11:24 PM Report Posted Thursday at 11:24 PM @gevertex My plane is in annual and I had some inkling the governor might need review. At last year's annual (MFSC) there was some variation after set-up and the manager told me it "might be getting tired". On some advice, I let it ride as the engine is de-rated from 2700 to 2500 rpm. The last several months I'd noticed some hunting of engine parameters, somewhat helped with mouse-milking the wastegate linkage (which actuator was overhauled last year). So, after some discussion with mechanics, on advice and statistics, this year I asked them to send it to a repair shop (West Coast Governor) for overhaul. Plane is about 1600 hrs and no log evidence of prior governor work. Heard back last week the governor "was in bad shape" and the estimate had increased. Currently trying to work the dance of parts shipment, timeline management, etc ("hey I need the plane, LMK if I can expedite things"). Don't have a full post-mortem or additional details. I figure it's parts going round-and-round and the macerator finally contacted the interferor and ground up some soft bits. Of course, these are just PP thoughts (hat tip @carusoam) . The local mechanic said they tend to prophylactically overhaul flight school/line service planes' governors sooner. Just a PIREP in case it helps. I know you had yours done a few years ago but who knows. There are apparently ways to bench-test these though I'm not sure everyone can. HTH David 1 Quote
gevertex Posted Friday at 02:44 AM Author Report Posted Friday at 02:44 AM I ended up sending out the governor for inspection. Lets see what they say. H&H Propeller (triad) did the overhaul, they can bench test it as well. Quote
gevertex Posted Monday at 03:21 AM Author Report Posted Monday at 03:21 AM So oddly, they were not able to reproduce this on their test bench. They did replace the speeder spring just in case. Not sure where to go from here. Quote
takair Posted Monday at 10:15 AM Report Posted Monday at 10:15 AM Do you have a plot of MP and oil pressure? May or may not present some hints. 1 Quote
gevertex Posted Monday at 06:52 PM Author Report Posted Monday at 06:52 PM 8 hours ago, takair said: Do you have a plot of MP and oil pressure? May or may not present some hints. The bar is where the drop occurred. What am I looking for? I could check other instances of this happening. It's really quick, I'd be surprised if MAP is fast enough to catch it. Quote
takair Posted Monday at 10:53 PM Report Posted Monday at 10:53 PM 4 hours ago, gevertex said: The bar is where the drop occurred. What am I looking for? I could check other instances of this happening. It's really quick, I'd be surprised if MAP is fast enough to catch it. Was curious if oil pressure was fluctuating when the RPM varies. That might indicate air….but usually the RPM would tend to go high. Regarding MAP, unrelated to the oil pressure, was wondering if that might surge with the RPM shift. In the plot, both seem to be going down? What do these look like over your original plots? Were you reducing power? Is red oil pressure? Wonder why that is drifting down? Quote
gevertex Posted Monday at 11:48 PM Author Report Posted Monday at 11:48 PM 52 minutes ago, takair said: Was curious if oil pressure was fluctuating when the RPM varies. That might indicate air….but usually the RPM would tend to go high. Regarding MAP, unrelated to the oil pressure, was wondering if that might surge with the RPM shift. In the plot, both seem to be going down? What do these look like over your original plots? Were you reducing power? Is red oil pressure? Wonder why that is drifting down? I don't see any variation in my oil pressure or MAP when this happens. Blue is oil pressure. Red is MAP. When this happens I am climbing at roughly best rate. This does not happen in cruise, except when I enrich the fuel mixture after lean finding. 1 Quote
gevertex Posted yesterday at 12:31 AM Author Report Posted yesterday at 12:31 AM 1 hour ago, takair said: Was curious if oil pressure was fluctuating when the RPM varies. That might indicate air….but usually the RPM would tend to go high. Regarding MAP, unrelated to the oil pressure, was wondering if that might surge with the RPM shift. In the plot, both seem to be going down? What do these look like over your original plots? Were you reducing power? Is red oil pressure? Wonder why that is drifting down? Oil pressure is decreasing as it heats up on the climb. MAP is decreasing as altitude increases. I am not changing mixture, throttle, or propeller controls during this time. 1 Quote
gevertex Posted yesterday at 02:29 AM Author Report Posted yesterday at 02:29 AM H&H agreed to swap my governor out, no charge. So hopefully that takes care of this... they were not able to find anything with the bench test. Quote
carusoam Posted 17 hours ago Report Posted 17 hours ago Late to the party… I do have O360 gov experience… ours are all very similar, unless you fly a Rocket engineered machine… where the failure mode goes full coarse pitch… for best glide distance… our govs are a few sub systems in one… 1) they have their own gear pump to supply pressure to adjust the pitch…. No way to measure the actual oil pressure within the prop during flight… 2) control valve… the thing that actually controls the oil pressure in the prop… 3) fly weights… the spinning device that activates (opens more and closes more) the control valve based on the speed of rotation of the fly weights… 4) the control knob that sets the fly weights… 1600 hours is not a lot of time to wear out this system… a certain amount of oil pressure needs to be supplied to the gov to allow it to work… gear pumps are pretty robust and can handle a lot of air bubbles if necessary… my old challenge… the O360 has a hollow shaft with a plug at the cabin end… if this seal fails, the gov is unable to build the necessary pressure to adjust the prop… the fifty cent seal only costs a few amus to replace… prop comes off, faulty seal gets pulled out, new seal pressed in place… prop goes back on… lots of sludge collects in the prop… the oil slowly circulates, but not enough to flush the system… lots of mechanical moving parts inside, fly weights are on a greased path… control valve too, so any dirt inside can keep them from moving correctly… consider what is happening based on the data… fly weights sticking, control valve sticking, or oil pressures fluctuating… PP thoughts only, not a mechanic… best regards, -a- Quote
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