Sudden Engine Stoppage

[John Wedge]

Would appreciate any thoughts, advice on this. PA 24-180, 0360 with 1400 SMOH, 390 since new Lycoming Cylinder kits, 160 hrs new plugs, about 10 hrs since annual. During annual - rebuild air box by WEBCO, prop gov overhauled, both mags sent for 500 hr service and new parts installed, high 70s compression all cylinders. Oil Aero Shell 100plus average 1qt 12-15 hrs. Fuel tanks are kept filled to top, hangared I flew it alone yesterday morning for 2 hrs, drained sump both tanks pre flight (did not drain into glass). I always burn off left tank first and I kept it on same tank for flight. OAT 48 degrees, easy start, normal run up, flew normal, no problem, EGT/CHT on UBG-16 normal. Returned and refueled left tank. Met with plane partner who asked me to fly with him as he had been out for several months on medical problem, plane sat on ramp for about 2 hrs while we talked. Went to fly, I again drained both fuel sumps before he cranked. He burns off right tank first so that is tank he selected (this tank had not been used that day). Normal crank, taxi, runup and takeoff. I was playing with UBG-16 and watching engine instruments during this time. OAT is now 50 degrees. He made one trip around pattern and touch & go and climbed out and we headed away from field, slowing climbing at 25/25 and leveled at 3,000 below a overcast and back to 23/23 and he had leaned it some. I am still messing with UBG-16 looking at temps - engine suddenly just stopped for split second - not a 1 or 2 cylinder misfire or stumble - just split second of nothing - then before either of us could move to change anything it resumed running normal at first and then slightly rough but not constant rough. Mixture to rich, fuel pump on, changed tanks & checked mags on both. I am looking at fuel pressure, mp & rpm and CHT/EGT while this is happening. We are 7.6 miles from field, turned back and engine is intermittent slightly rough for about another 1-2 minutes (not sure as time kind of stands still). During this he is flying acft and I am still watching all engine instruments - I see NOTHING changing, MP is steady nailed on 23. I pull carb heat on and normal change in engine and lose slightly over 1 inch MP, leave in on for about 45 seconds and shut off, MP back to 23. We stayed at 3,000 over field and then shut off fuel pump, I leaned it out again, everything good, changed tanks, everything good. Flew several 360s over field and all well - departed away again and went out about 30 miles and back and everything good and normal, changed tanks again when near another airport and returned home field did one full stop & back taxi and one touch and go and final landing and all normal.
When sudden stoppage occurred I had immediately looked back to the fuel pressure so if there was - and I assume there must have been a quick change in MP from the 23, I did not see it because when I saw no change in fuel pressure I looked up at MP & RPM before going back to UBG-16 and it was on 23 inch.
Was it- slug of water, carb ice??? My impression was that it was not fuel related but was "electrical" ??? Or was it "just one of those things that happens to keep us on our toes and then goes away)????
Any advice / suggestions on future course of action???
Thanks.
John

[Jay]

Sounds like you did a lot of work on your engine. How old is the fuel pump?

Jay

[John Wedge]

Uuuhhh - don't know - don't "remember" any problems with it, would guess it is / was one put on at OH. Have forgot a lot in 27 yrs with it. Will check books at hangar tomorrow for that.
John

[steen]

Best guess what you reported.....big slug of water from right tank. MP would stay steady as throttle opening does not change and RPM did not stop. I know of no
electrical "thing" that could cause this (thank goodness for redundancy). A slug of water followed by dribs and drabs finding their way out of the tank would cause
what you describe.
Steen

[N3322G]

John,

Thinking about the water thing - even though you drained. Next time you fly and before you fuel, put it in the hangar and shine a flashlight in the tanks and try to see if there are wrinkles in the bottom of the tanks - there were in my twin until I had them all changed with Aero Tec tanks which seems to fit better than the originals ... or they were better installed - Clifton did the replacements.

Also, I know the twin is placarded to sump before first flight and after last one this has really kept a much cleaner set of sump filters - don't know if it is the same on singles.

Hope this helps.