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Desmor944(at)aol.com
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 Posted: Sun Jul 16, 2006 5:42 am Post subject: Another Engine Out Landing |
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Gang,
Here is a scenario to rival one of Jeff's EP of the Day thought provokers. But no hypothetical; this happened last Tuesday evening. Aircraft is a stock 1985 CJ with Huosai engine.
Normal pre-flight, with sumps clear, half tanks, and 14 liters of oil. Perfect for a planned half-hour flight around Cape Cod. About 15 minutes into the flight, and as I was turning to head back, the engine skipped a few beats as though the mags had been switched off then back on. Engine seemed to be running fine again, but since this was a first in five years of ownership, I headed straight for home. Instrument scan looked normal except that fuel pressure was about a needle width higher than usual. About a minute later, a slight roughness develops, and manifold pressure drops a bit. Fuel pressure has now increased from 0.5 kg/cm to 0.7. Oil pressure, oil temperature and CHT all still normal. Add throttle and begin a gradual climb. Roughness increases so suspecting an overly rich mixture try leaning without success. Full rich helps a bit, wobble pump doesn't. Engine starts surging as though plugs are fouling and then clearing. Add more throttle.
Arrive over home field (5B6 - 2280' x 40') on a high downwind at 2300 feet agl with engine very rough, missing intermittently, and near full throttle position for 700 mm. Fuel pressure is now 0.9 kg/cm. All other indications still normal. Figuring that I now have the field made no matter what, start to reduce power slightly for descent and the engine quits. Spiral to 1500' agl abeam the numbers, tight pattern at 160 kph, drop gear on short final, extend flap crossing the tree line, and make uneventful landing. Turn off runway at the fuel pumps in case I need fire extinguishers there. Prop finally stops windmilling as I brake for the turn. Exit aircraft and notice oil streaming from both exhaust stacks.
Walk home, get the golf cart, and tow the plane back to its hangar.
Now this is the part that has me scratching my head. Assuming fuel contamination, sample the gascolator and get a tube full of ENGINE OIL! Have a neighbor watch the now open gascolator drain while I operate the wobble pump, and he says that a couple of cups of oil came out before in turned into a thinner black liquid. Sumped the header tank and it is black with oil. Wing tanks still clear. Checked the oil tank and it is down about 4 liters in a half-hour. Not much more than the usual amount of oil on the belly.
Yesterday's disassembly found oil in all fuel lines and the carburetor. The only place I can think of where oil and fuel systems come together, and oil is at the higher pressure is at the pumps. I removed the fuel pump, and the cavity above the bearing was full of oil. Is this normal? Could a bad seal in the oil pump have allowed high-pressure oil to force its way into the fuel pump? Could a bad seal in the fuel pump have allowed the oil in if it is supposed to be above the bearing under pressure? It does not appear that oil was coming out of the fuel pump leak-off line.
Dennis, Doug, Walt and all; any thoughts? If this happened once, it can happen again. What to look at next, and how to avoid a repeat?
Rich Desmond
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david(at)warbirdrebuilder
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| Posted: Sun Jul 16, 2006 7:29 am Post subject: Another Engine Out Landing |
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Rich
Is your oil dilution valve still on the firewall? I remove them from the CJs I maintain/build for just this reason. Not to say that is your problem but maybe? Just my 2cents.
David
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Desmor944(at)aol.com
Sent: July 16, 2006 4:44 AM
To: yak-list(at)matronics.com
Subject: Another Engine Out Landing
Gang,
Here is a scenario to rival one of Jeff's EP of the Day thought provokers. But no hypothetical; this happened last Tuesday evening. Aircraft is a stock 1985 CJ with Huosai engine.
Normal pre-flight, with sumps clear, half tanks, and 14 liters of oil. Perfect for a planned half-hour flight around Cape Cod. About 15 minutes into the flight, and as I was turning to head back, the engine skipped a few beats as though the mags had been switched off then back on. Engine seemed to be running fine again, but since this was a first in five years of ownership, I headed straight for home. Instrument scan looked normal except that fuel pressure was about a needle width higher than usual. About a minute later, a slight roughness develops, and manifold pressure drops a bit. Fuel pressure has now increased from 0.5 kg/cm to 0.7. Oil pressure, oil temperature and CHT all still normal. Add throttle and begin a gradual climb. Roughness increases so suspecting an overly rich mixture try leaning without success. Full rich helps a bit, wobble pump doesn't. Engine starts surging as though plugs are fouling and then clearing. Add more throttle.
Arrive over home field (5B6 - 2280' x 40') on a high downwind at 2300 feet agl with engine very rough, missing intermittently, and near full throttle position for 700 mm. Fuel pressure is now 0.9 kg/cm. All other indications still normal. Figuring that I now have the field made no matter what, start to reduce power slightly for descent and the engine quits. Spiral to 1500' agl abeam the numbers, tight pattern at 160 kph, drop gear on short final, extend flap crossing the tree line, and make uneventful landing. Turn off runway at the fuel pumps in case I need fire extinguishers there. Prop finally stops windmilling as I brake for the turn. Exit aircraft and notice oil streaming from both exhaust stacks.
Walk home, get the golf cart, and tow the plane back to its hangar.
Now this is the part that has me scratching my head. Assuming fuel contamination, sample the gascolator and get a tube full of ENGINE OIL! Have a neighbor watch the now open gascolator drain while I operate the wobble pump, and he says that a couple of cups of oil came out before in turned into a thinner black liquid. Sumped the header tank and it is black with oil. Wing tanks still clear. Checked the oil tank and it is down about 4 liters in a half-hour. Not much more than the usual amount of oil on the belly.
Yesterday's disassembly found oil in all fuel lines and the carburetor. The only place I can think of where oil and fuel systems come together, and oil is at the higher pressure is at the pumps. I removed the fuel pump, and the cavity above the bearing was full of oil. Is this normal? Could a bad seal in the oil pump have allowed high-pressure oil to force its way into the fuel pump? Could a bad seal in the fuel pump have allowed the oil in if it is supposed to be above the bearing under pressure? It does not appear that oil was coming out of the fuel pump leak-off line.
Dennis, Doug, Walt and all; any thoughts? If this happened once, it can happen again. What to look at next, and how to avoid a repeat?
Rich Desmond
--
No virus found in this incoming message.
14/07/2006
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rvfltd(at)televar.com
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| Posted: Sun Jul 16, 2006 8:14 am Post subject: Another Engine Out Landing |
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Has your oil dilution system be properly removed/disabled? Is it possible that oil is reaching the fuel system via this point? Yes I know it's going the wrong way but I have seen some crazy plumbing. Just a thought.
Was there oil in the fuel line going TO the pump? I would bet not.
While it is possible for the oil to migrate into the fuel via the shared pump drive I have never seen it before. Course I had never seen a HS6A totally pack up in flight before either! A simple test might be to remove the oil and fuel pump in one unit, cap off the "out go" side and pressurize the "in" side fitting fuel pump with LOW pressure shop air and submerge the unit in water, if you are getting bubbles out of the oil pump you have found your problem.
Look at your vol #3 Huosai engine IPB on page 179, Fig 16-5-3. Note # 7, which is P/N 14.211.91 and in the translated version of the IPB is called a "check valve" (looks like a seal in the dwg). Page 107 will give you a better idea about the mating of the two units. Page 167 shows the blow up of the fuel pump and it's seals.
Let me know what you find.
I plan to bring the CJ to OMK on Tuesday and start tearing down the engine, my gut feeling is that I will not have to go further than the nose case to find what failed.
Always Yakin,
Doug Sapp [quote] --
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ByronMFox(at)aol.com
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| Posted: Sun Jul 16, 2006 8:31 am Post subject: Another Engine Out Landing |
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Glad to hear you landed safely, Rich. Please keep us informed as you sort through this problem. Thanks, Blitz
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wlannon(at)cablerocket.co
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| Posted: Sun Jul 16, 2006 9:14 am Post subject: Another Engine Out Landing |
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Rich;
Very Interesting!!
As David has mentioned there is another interface point between fuel and oil. If the oil dilution system is left installed there is a potential for failure. I too remove this system entirely.
However in reading your post incident analysis it appears most likely that the source of the problem is where you found it, the oil pump / fuel pump common drive arrangement.
I think you are on the right track. Will look at the systems on Monday and let you know if anything comes to mind.
Walt
[quote] ---
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