912 engine 'Blip' just after take-off

by John Hood in 912 / 914 Technical Questions 11 years ago

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Re: 912 engine 'Blip' just after take-off

by Kevin Stewart » 11 years ago

Kevin Stewart

5 184 0

Hi John,

I had a similar problem on my UK Eurostar a couple of years ago. It turned out to be some debris in one of the carb float bowls getting sucked up into the main jet. These are easy to access and remove on the Eurostar. They are held in place with a clip underneath. The Rotax maintenance manual explains all.

With reference to Roger's comments about cruise RPM, the Eurostar has its max engine speed restricted in the UK. The Light Aircraft Association operating limitations document which applies to group A Eurostars in the UK specifies acceptable propeller types and pitch as well as the maximum continuous RPM which is 4800RPM.

I have check this with the LAA and they confirmed the above. My takeoff roll is short enough as it is, I cannot imagine what it would be like with a finer prop pitch.

Kevin

Thank you said by: John Hood

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Re: 912 engine 'Blip' just after take-off

by John Hood » 11 years ago

John Hood

1 5 0

Thanks Kevin.

Yes, I have a constant pitch wooden VZLU prop fitted, and don' think the problem's related to max engine revs, and even if it was, there's not much I can do to change it. I've now changed all of the fuel lines and cut the old ones open to check for obstructions, but found nothing. I've also checked the plug gaps but again they seem OK, and all of the plug caps have also been renewed. My gut feel is still momentary fuel interruption, but the fuel in the carb bowls looks fine. I've managed to borrow an endoscope, and plan to try to inspect the inside of the fuel tank for any possible obstruction. The only suggestion I haven't tried yet is to get the carbs balanced, which I plan to do in the next couple of weeks or so. It's really frustrating though, and is spoiling my flying, as I'm constantly waiting for the engine to 'cough'!

Thanks for your help anyway.

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Re: 912 engine 'Blip' just after take-off

by John Hood » 11 years ago

John Hood

1 5 0

Afternoon gents!

Just been having a beer with a friend, and as usual my ongoing problem with the 'engine blip' cropped up in our conversation. He suggested it could be due to an interference in the fuel tank venting system, and I notice that this is achieved by a venting pipe routing into the tank drain pipe. Do any of you have any experience of this problem, and indeed, do you think this could feasibly be responsible for the engine 'blip' shortly after take-off? I.e. poor venting causing a vacuum in the tank and therefore momentary fuel starvation.

Thanks.

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Re: 912 engine 'Blip' just after take-off

by Roger Lee » 11 years ago

Roger Lee

125 5.12k 4.53k

Hi John,

I seriously doubt this is your problem. You either have a vacuum or you don't and it isn't just a blip. It starves the engine of fuel. It just doesn't come and go in a second or two and then just go away.

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

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912 engine 'Blip' just after take-off

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