timb
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Post by timb on Sept 21, 2017 19:47:38 GMT
First posted under "Oshkosh Rotax Seminar" sorry should have created a new thread.
My sudden loss of oil pressure on a cross country trip followed quickly by gearbox vibration has now been linked. Because of several factors it took six weeks to determine it was an oil pump problem. Along with ordering a new oil pump my gearbox was sent to California Power Systems so Bryan Toepfer could rebuilt it because of the vibration problem.
When the gearbox was opened he discovered a friction washer was missing and believed to have been chewed up and sucked into the oil pump thus causing the very low oil pressure.
I was told the friction washer coming apart has happened before but very rarely.
I now have a completely rebuilt gearbox and a new oil pump but the problem is compounded by the fact that we have found bits of debris in the bottom of the oil tank, which I believe indicates it got past the oil filter?? and if that's the case is there still more that could be sitting in the crankcase?? to later cause the same problem or worse??
The mechanic is following instructions to clean the oil tank and flush out the oil lines and the oil cooler has been sent to be cleaned and flushed.
After hurricane Irma left us without electricity we came back to Albuquerque hoping to fly our plane home, it's been 2 months 5 days and counting, we were looking forward to flying our plane back home but after finding out about the debris in the oil system I'm a little apprehensive.
I've asked if Rotax "Kodiak" will give me some assurance that it will be safe to fly and also to help defray some of the costs, waiting to hear back.
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Post by Flocker on Sept 21, 2017 20:10:30 GMT
I now have a completely rebuilt gearbox and a new oil pump but the problem is compounded by the fact that we have found bits of debris in the bottom of the oil tank, which I believe indicates it got past the oil filter?? and if that's the case is there still more that could be sitting in the crankcase?? to later cause the same problem or worse?? I think the oil tank is designed to let some things settle at the bottom. (I know lead will settle there) Did they cut open your filter and inspect the element? Do you send off your oil samples for analysis? I'd purge the system and filter the oil coming out the drain hose to see if anything turns up there.
Stroudj, what do you think?
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timb
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Post by timb on Sept 22, 2017 23:59:24 GMT
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timb
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Post by timb on Sept 23, 2017 0:04:58 GMT
The engine has about 17.5 hours since the last annual and the first 14 hours burned mogas so there was no lead at the bottom of the oil tank just that small amount of grit probably from the missing friction washer.
The old oil pump housing with attached oil filter will be sent to the Rotax people to examine. I have not previously used oil analysis but plan to next oil change. As far as checking now, I don't think it would tell me much because during all this changing parts etc. the mechanic's been pouring fresh $12 a quart oil in like it's water. I have asked the mechanic to save any debris found, but unless I stand over him he does not seem to focus on detail. Hopefully putting everything back together tomorrow and try again.
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Post by stroudj on Sept 23, 2017 20:09:23 GMT
I now have a completely rebuilt gearbox and a new oil pump but the problem is compounded by the fact that we have found bits of debris in the bottom of the oil tank, which I believe indicates it got past the oil filter?? and if that's the case is there still more that could be sitting in the crankcase?? to later cause the same problem or worse?? I think the oil tank is designed to let some things settle at the bottom. (I know lead will settle there) Did they cut open your filter and inspect the element? Do you send off your oil samples for analysis? I'd purge the system and filter the oil coming out the drain hose to see if anything turns up there.
Stroudj, what do you think?
After reviewing the posts and Rotax maintenance manuals I question if the engine is airworthy. The oil is forced to the oil tank by blow-by from the piston rings. The oil tank has a screen that traps any large contaminants. The oil is then pull from the oil tank thru the oil cooler to the oil pump. The oil is then pushed thru the oil filter to contain the small contaminants then to the passages to the crankshaft and camshaft it then falls to the crankcase and is forced back into the oil tank. Since the oil pump is before the oil filter the small contaminants damaged the oil pump by wearing the the rotor, rotor piston and oil pump housing, increasing the clearance between the oil pump parts causing low oil pressure. The question: Did the oil filter capture all of the small contaminants before they got to the crankshaft and camshaft? The answer: If the oil filter did not bypass it should be okay. If the oil filter did bypass, the small contaminants were push thru the engine, damaging all moving parts. Solution: Flush and clean the lubrication system according with the 912i MM Page 40. If flushing and cleaning fails to clear the oil of small contaminants replace the engine or overhaul the engine. My thoughts: I would not fly cross country until engine is found to be clean of all contaminants and no damage to the engine is found. Thanks, Jim Stroud |
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timb
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Post by timb on Sept 23, 2017 22:50:04 GMT
Jim, thank you for your careful analysis of my problem, after flushing everything we can with the oil system I'm waiting for the mechanic to put it all back together again. If the ground tests go well I plan on staying in the pattern a reasonable length of time then venture out solo and check out some of the beautiful area around Albuquerque. If I can fly trouble free for 4 to 6 hours around the area I'm heading home to Florida.
Thanks, and I'll let you know how it works out.
Tim Brown
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timb
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Post by timb on Sept 30, 2017 1:57:55 GMT
To those following this 912is problem, I think I finally understand what happened. A friction washer in the gearbox failed and fell loose in the gearbox and got chewed up into little pieces. The gearbox is bolted to the engine case and gets its lubrication through a small hole between it and the engine case. The oil goes through this small hole and fills the gearbox up to a level where the gears can fling the oil to lubricate the gears. The excess oil returns to the engine case through another small hole, so the little pieces of chewed up gasket flowed into the bottom of the engine case where they were forced out the bottom drain into the oil tank. Some pieces settled to the bottom of the oil tank, while some got sucked back into the oil pump via the oil cooler. Too much debris plugged the oil pump up and caused the low oil pressure. After cutting open the oil filter, it was clear that that's where most of the debris ended up. The oil filter did its job! I bought a large funnel with a very fine screen, went flying, and then drained the oil tank through the funnel screen and replaced the same oil back into the tank again, over and over and over to filter out what debris that was left in the engine case. I have been told this washer has failed before but "very rarely". The debris has been screened out and we plan on flying back to Florida starting Sunday, weather permitting. It's been two and a half months and a big learning experience. Glad to be back flying! Thanks to Bryan at California Power Systems and Dean at Lockwood Aviation for all the help finding the problem even though it took this long. Tim    Attachments:
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Post by stroudj on Sept 30, 2017 2:40:44 GMT
I suggest that when you get back to Florida, have an oil sample tested to determine if there is excess engine wear. I would also take a sample every 25 hrs until you can determine that there is no unusual engine wear. What worries me is the microscope debris.
Have a safe trip back to Florida. I live in Ocala, where do you live?
Jim Stroud
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Post by Glenn on Oct 1, 2017 13:49:24 GMT
To those following this 912is problem, I think I finally understand what happened. A friction washer in the gearbox failed and fell loose in the gearbox and got chewed up into little pieces. Tim Tim, Wow, my fingers are crossed for you. Thanks for the update. Glenn |
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timb
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Post by timb on Oct 5, 2017 14:03:25 GMT
Just thought I'd let you all know we made it safely back home to Florida. The engine ran fine, the only problem was the mechanic in Albuquerque did not get the gearbox sealed properly and two bolts were loose, so I had an oil leak streaking down the pilots side all the way to the tail. I flew down to Lockwood yesterday where they removed the gearbox cleaned the surfaces and torqued it on properly and changed the oil & filter. Dean Vogel at Lockwood said they have seen other friction washers fail in the gearbox. I'm relieved to have this problem solved, and hoping for some trouble free flying. Lockwood & California Power Systems are working to get me some compensation from Rotax. Tim  |
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Post by Glenn on Oct 5, 2017 14:19:30 GMT
Tim,
Good news!! Now let's see if Rotax will step up and handle this.
Glenn
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Post by Cluemeister on Oct 5, 2017 16:44:59 GMT
Glad you made it home safe!
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Post by buzz on Oct 5, 2017 17:37:29 GMT
This entire issue concerns me. Its a serious issue when your engine loses oil pressure. Tim you say this is a known issue with Rotax. Are they working on a fix for all of us?
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timb
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Posts: 117
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Post by timb on Oct 5, 2017 18:16:05 GMT
I really don't know if they are looking for a fix, since they say it is rare and happens to engines with a possible vibration issue set up by harmonics.
Dean Vogel said the new 915is Turbo has a newly designed gearbox, but he did not have first hand knowledge yet.
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Post by Glenn on Oct 5, 2017 19:35:34 GMT
It is very true that vibration can cause engine and gearbox issues but it would be nice to hear they're actually doing something to find the cause and prevent future similar failures. A list of gearbox serial numbers would be nice.
Glenn
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