Rotax 582 in Aviatika problem

[bluesmancoops]

Flew from Morning Star (western Cape) to 20km east of George (southern Cape) in 3hours 10 minutes. 3 minutes from landing, the engine suddenly cut, pumping the throttle a few times still wouldn’t get it started again, eventually the windmilling prop started the engine again but it missed and spluttered just above idle eventually cutting on short finals. I landed with a dead stick landing and restarted on the runway. It started immediately and gave maximum power again. I removed the fuel filter and found a bit of dirt but not enough to cause this problem. I emptied the fuel tanks (over 15 litres of fuel remained) and flushed them out and test flew it again, again cutting out and eventually restarting and spluttered and dead stick landed again and restarted immediately on the runway giving max power again.
I fitted an electronic fuel pump as I felt that it seemed like fuel starvation and test flew it again, again having engine power loss but did not cut out completely, remained just above idle, spluttering, on landing, gave max power again. I Have checked the fuel lines which check out okay.
Test running at max power (6800RPM) on the ground checks out perfect with no RPM drop but I have only done this as a normal power check for a short period but under load, I can just take off and within about a minute and a half, the engine cuts.
I have paid special attention to the fuel cock to make sure that it is open correctly but this has made no difference.
Each time on landing, I have restarted the engine and got max power immediately, test run up and down the runway with no problems but as soon as I take off, approximately one and a half minutes later, the engine cuts.
It does not miss fire like a plug lead or spark plug breaking down but definitely gives symtoms of fuel starvation. When the engine cuts whilst in the air, throttling right back (to give the fuel bowls a chance to fill again) doesn’t make any difference to the spluttering.

[Dre'man55]

I had a similar problem on my quad, Breather on the fuel cap was not working. So after a while, about same time as you fuel can't pull through. Once you slow the flow for a while pressure in the tank normalises again and you have fuel until there is a vacuum in the tank again. Not sure where the breather is but would check that.

[Wargames]

Does this happen only while decending??

[tandemtod1]

From your thorough description of your problem, it does seem like it is fuel system related.
Do the basic checks first. Check that the tank is effectively vented to atmosphere and make sure the breather is completely clear. If you draw a partial vacuum in the tank you will get this kind of symptom. Check that the pick up line inside the tank is clear of any obstructions and blow through all the lines if you can to verify that they are clear. If this all checks out OK then answer my questions and I will give you more things to check.
Does your aircraft have an airbox on the caburettors and if so, do you get ram air whilst flying?
Did you have this problem before you fitted the electric fuel pump?
Was the extra pump fitted to try and solve the problem?
Is the electric pump fitted inline with the diapham pump or in parallel?
I hope you find the problem without too much trouble and while there is a doubt, don't take too many risks

[tandemtod1]

How high did you get in the quad before the fuel starvation kicked in?

[Dre'man55]

How high did you get in the quad before the fuel starvation kicked in?

About 90kmh, only get airborne at 125

FYI Rotax motor as well, strangely enough fuel starvation is not necesarily different because motor is airborne.

[Morph]

Does your fuel tanks have venting tubes on the top of the tanks ala Bush Baby. These are supposed to point forward to give the tank positive pressure while in flight. If they face backwards there is negative pressure and the fuel stops flowing. This won't happen on the ground once standing still because there in no airflow across the vent and normal atmospherical pressure then acts on the fuel.

[bluesmancoops]

thanks for all the replies, everything mentioned has been looked at, Morph, the vents stick straight upwards but with the electric pump, this should eliminate that problem.

[nickjaxe]

I believe a coil on the way out can give symptoms like that, what about Icing,

After you landed dead stick did you drop a carb bowl to check the levels.

Nick.

[bluesmancoops]

I believe a coil on the way out can give symptoms like that, what about Icing,

After you landed dead stick did you drop a carb bowl to check the levels.

Nick.

straight after touchdown the plane starts first time - have checked the bowls and they are full

[extra300s]

I thought the problem has been found?

[Duck Rogers]

If it has EGT gauges fitted, check if the temps go up when the engine starts spluttering. If they do, it's almost 100% fuel related. If not, it's electrical.

[Duck Rogers]

Here's something else you can look at.....

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page2.jpg (81.96 KiB) Viewed 3053 times

[CFD]

The original owner of the aircraft mentioned that he used to have these problems and traced it to a poor quality fuel cock that seemed to close itself in flight! (happened to me too an the same aircraft! at Mstar!).
He took the tap out and simply had a straight-thru system with no cut-off valve/tap. The 2nd owner put the fuel cock back! Cant remember if he had issues but if I was you it is a simple case of replacing this with a better version, or even leaving it out completely!

Previous owner - ZU-AUK