Earthstar Forums

On Wednesday, on a flight with the former owner of my Thunder Gull JT2, we had four momentary power losses within less than three minutes. Fearing an engine seizure was in the works, I made a precautionary landing on El Mirage dry lakebed.

Here's a cockpit video of the episode:
http://www.youtube.com/watch?v=MbGEcEFZ5a0

We removed the wing and trailered the plane back to my airport. Yesterday I opened the exhaust ports and a Rotax expert (factory training)saw no evidence of a seizure. The engine was rebuilt 65 hours ago and looked like it just came out of the shop. The plugs showed the mixture was perfect. The carb bowls were pristine, as were the fuel lines and see-thru filters. I drained the tank dry, running the four gallons of fuel remaining through a Mr. Funnel into a fuel can. No water or debris was found. I poured that gas into my truck and drove home on it.

We were on the Mikuni fuel pump throughout the flight. I didn't switch on the electric pump. It was pretty bumpy over the hills just before we reached the lakebed.

I welcome your ideas, especially if you've encountered the same thing.

Dick

i had three momentary engine outs within less than three minutes
yesterday. a 5yr old 2stroke aircooled 350cc, no rebuild yet, heavily
abused recently by someone else, stayed below 40kmph for a half hr,
the pneumatic brake fluid seems gone - brakes harshly, gearbox loose
and a bit leaky with few drops of water, oil seems ok, but the piston
sound is way too hollow and scratchy. will update further once i get
it to an expert

rc

What comes to mind is the possibility of a fuel line pinch? Did the tank
move in the turbulence? Did you shove things around in the rear of the
aircraft. I know one situation where a pilot had some clothes packed near
his fuel line and when he moved the clothes, fuel flow stopped.

Have you checked the fuel pump? Has it been rebuilt?

Was the power losses abrupt or did the power taper off?

What was you elevation and temperature (were you at a very high density
altitude)?

Were you flying upside down due to the turbulence ;-)?

Is there any wear of the needle (around the clip that holds it at a certain
level, for example). It is possible that this or some other part of the
carburetor moved due to the turbulence and because something is worn. Are
the jets fully screwed in? Are your floats compromised by a leak or old
age. Is there any wear in the rod which controls the float movement (or the
fitting it slides into).

I've had situations where the fuel filter was compromised, but that resulted
in low full power performance and performance loss at higher altitudes, but
nothing abrupt. That was also with fuel injection, which has a different
set of issues.

-Alan



_____

I will just add my 2 cents worth.
Fuel restrictions could be one thing. (Allen did a good job of explaining that)
If the engine stuttered with your power loss it could be a bad electrical connection some where. You said the engine came out for a rebuild a while back. perhaps something didn't get tightened up.
If it was a lubrication problem your plugs should have shown that.
Did your temps move out of regular zones when you were having problems?
Fred

Check inside your fuel tank for debris blocking the fuel intake line.

Mike

Good idea. I had this happen to me.

-Alan Cossitt

>From my iPhone. Please excuse typos and terseness.

The only problem I ever had similar to yours was caused by the ignition
sysytem.. In my case I had one of the ignition systems shorting out and the
engine would run on both plugs than on only one plug. I could feel the
difference in engine power in flight but the RPM change wasn't quite as dramatic
as yours'. It was a broken wire under some shrink wrap that would make contact
most of the time unless there was turbulance. Just a thought.

Ted

Thanks. Several viewers have suggested an ignition fault. You're the first to
describe actually experiencing it. It should be easy to check out. It makes the
most sense. The losses were too transitory to be a fuel interruption.
 Dick O'Reilly

Dick,

I viewed the video and heard what you were experiencing. I noticed that the altimeter was showing 6000-6500', and you had two people aboard. The engine sounded like it was running near full throttle, and I suspect you were getting a fuel flow problem. I noticed that Leaf Airfoils or Wicks has a higher output fuel pump for Phantoms and similar aircraft that have to pump the fuel up high and long distance. Rotax also gives a fuel pump pressure range, and it might be interesting if it was measurable inflight. I run a 503 also, but in my single seater at sea level and chilly Northwest temps, it doesn't run hard at all. Still, I don't like hearing about loss of power issues on the same engine I'n running.

kb

I know others have had problems at high altitudes due to low fuel pressure. Why the have elec. Fuel pumps to back up mechanical.

-Alan Cossitt

>From my iPhone. Please excuse typos and terseness.