Engine quit

by Robert J. Dean in General Tech Discussion 5 years ago

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Re: Engine quit

by James Ott » 5 years ago

James Ott

22 323 359

Since this is a Rotax forum I was assuming this event was with a Rotax engine, but looking closer at the YouTube video it says this was a Piper Sport, which I believe has a Continental engine. My comments above were directed at Rotax 912/914 powered aircraft. Not saying vapor lock is not an issue with Rotax, but it is a somewhat different animal, especially with the fuel bypass line installed.

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Re: Engine quit

by Mitchell Whatley » 5 years ago

Mitchell Whatley

0 5 0

Not a single SportCruiser was delivered with a Continental engine. A very small number were produced with the Jabiru 3300 engine, but this aircraft (N422PS), manufactured in May 2010, and all others were delivered with the Rotax 912 ULS engine. See http://www.aviationdb.com/Aviation/Aircraft/4/N422PS.shtm

As for the fuel return line, this aircraft already had it installed as it was manufactured after May 14, 2009. And even if it had been an earlier model without a fuel return line, compliance with Safety Alert (SA-SC-006) issued October 16, 2017 was immediately mandatory in an attempt to mitigate this exact problem.

Those who routinely operate the Rotax 912 in high-temperature environments with multiple takeoffs and landings in the same day recognize that having a fuel return line with a restrictor orifice is not a silver bullet. Under some conditions, the restrictor does not allow enough flow to remove the vapor. The ONLY way to avoid vapor lock in the Rotax 912 ULS is to ensure that the fuel temperature under ambient pressure conditions does not exceed the fuel system's ability to purge fuel vapor.

Rather than try to guess what those conditions might be, when it gets hot outside and the aircraft will quick turn, many pilots simply use 100LL (RVP 6.5) until summer-blend fuel is available. But even then, hot summer days and heat-soaked fuel may prevent the use of MOGAS at all, especially if all you can get has an RVP of 9.0 (found in most rural Texas counties).

The procedures and checklist I outlined above are the result of my experience (17,000+ hrs total time, 1,100 hrs with Rotax 912) and that of many others who have been confronted with a fuel-starved Rotax 912 at the most inconvenient times. My intent is to bring this issue to light and open the forum for discussion. Others may have perfected better and more effective strategies for dealing with vapor lock. I've just presented the procedures that I've found effective.

Those who rarely if ever try to take off under such high-temperature conditions with a heat-soaked engine should still be aware of the problem and how to deal with it. I've had to remove the top cowling and use ice to cool down both the mechanical and electric fuel pumps just so I could start the engine when I wasn't willing to drain the gas I had to buy 100LL at $7.00 per gallon.

Under these conditions, I generally leave the electric pump running after confirming that the mechanical fuel pump works because keeping the fuel pressure at its maximum also keeps vapor formation at a minimum. And that's also why I use the Facet Cube 40106 (7.0 psi max) rather than the stock 40105 (4.5 psi max) just as Roger mentioned earlier. These pumps are designed to run continuously for hours on end and usually last for many years (usually, not always).

I know there are many others who have had similar experiences. How did you deal with them?

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Re: Engine quit

by Roger Lee » 5 years ago

Roger Lee

127 5.21k 4.79k

Many of us live in Arizona in the US where spring and summer temps are between 95F - 110F. We only have 91 oct. with 10% ethanol. Most of us have no issues. 100LL is more resistant to the vapor lock situation, but it can still happen if things get hot enough. You can have low pressure after landing and letting the plane sit for 45 - 60 minutes. This can usually be limited with a short time on the ground with higher than normal idle rpms to get cooler fuel up to the heat soaked fuel lines on top of the engine. When I would go to breakfast during the summer months and let the plane sit while I ate I would come out and the fuel pressure would be 1.5 psi. Just start the engine and let it run up around 2300-2500 rpm and taxi to the active runway to get cooler fuel up in the hoses faster. I never had an engine stumble.

Set the cowl up to allow hot air under the cowl to escape during shutdowns and better air flow during flights.
The low wing planes seem to have more issues than high wings. At least this is what I see on the internet and from calls.

As bad and sad as that crash is in the video that was pilot error from too sharp a turn too low. A plane lands just fine with or without an engine running. Just ask a glider pilot. You just get one shot when the engine is off. I used to practice engine off landing all the time. They aren't a big deal.
During many of our Ultra Light days back in the early 1980's dead stick happened fairly frequently for some.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Engine quit

by Alan Arnold » 5 years ago

Alan Arnold

20 188 145

Several years ago, at Sun n Fun, I was examining a Eurofox, a similar plane to my Highlander. I noticed 2 2" vent holes with wire mesh on the top of the cowling. I asked the vendor what they were for. He said cooling after engine shutdown to prevent vapor lock. I asked Gary of Just Aircraft if those holes would hurt inflight cooling in any way and he said it would not. I modified my cowling soon after returning home. Since I live in southeast Texas I think those Eurofox folks came up with an easy fix for heat soak caused vapor lock.

Alan

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Re: Engine quit

by ERNEST BITTEN » 5 years ago

ERNEST BITTEN

7 37 78

I live in the Pacific NW south central dessert where it sometimes starts to get hot in early spring. I experienced vapor lock in the air two years in a row using 91 octane no ethanol gas. I now mix 50/50 mogas with 100 LL as mwhatley55 suggested.

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