Rotax 912 fuel in sump question

[thys bas]

A friend of mine wanted to go fly around the windsock this morning. When he pulled the dipstick, the oil tank was filled with petrol! Further investigation showed he forgot the fuel valve from the high wing tank open. More flooding inside the engine was discovered, even the sump was full of petrol

It seems one of the needles in a carburettor could be leaking, is this possible? has anybody experienced this problem before? What must he do now?

[Dobbs]

I recently read of an exact situation on the EAA web site, although they do not dwell on the cause, the question was, did the engine need to be stripped down to confirm any damage etc, and the answer was an emphatic no, change the oil, they did not mention anything about the filter, but no harm in replacing that as well, and off you go.

In fact, it seems to be common practice in the colder climates of North America, that some oil is put into the petrol on shutting down to thin it out for a restart the next time the plane is used. Soon after reaching operating temps the petrol volatilizes and the oil reverts to its designed viscosity.

[Dobbs]

Ooooops, that should read - fuel in the oil/ sump

[thys bas]

Thank you Dobbs, I can not think that any permanent damage was done to his engine, but it is good to have confirmation and input from others.

All we have to do is find out why it happened. My guess is a stuck needle or perhaps damaged seat in a carburettor. Fuel just kept flowing into the carb, the silinder, past the rings into the sump and then into the oil accumulator. About 10 liters of fuel went that way in about a week.

[Boet]

Do not use the float chambers as petrol taps. Get into the habit op opening and closing the petrol taps before and after each flight. Never had this problem. That is why the aeroplane have petrol on and off taps.

[Dobbs]

And there you have it from the man what knows

[thys bas]

Dankie Boet, maar lees weer my eerste post. Die arme man het die kraan oop vergeet, nie dat hy dit elke dag oop los nie.

Daar is mos fout as die petrol deurloop, nie waar nie? As mens nie weet wat dit veroorsaak het nie kan mens mos nie gaan vlieg nie.

Wat sal in die lug gebeur, sal die een helfte van die enjin dan te ryk loop? Sal dit vrek? Sal niks gebeur nie?

Gelukkig vlieg ek met C85, net een vergasser En ek het ook al die kraan oop vergeet, niks het gebeur nie. Trouens, dis soms beter as mens die kraan oop los as die stopover net vinnig koffie drink en dan weer vertrek is, want dit hou die drukking op die brandstof en die mogas vorm dan minder borrels in die pype. Ek mag verkeerd wees, dit voel maar net so. Die Rotax dink seker ook anders daaroor.

[Boet]

Het die enjin se brandstoftoevoer n "restrictor" tussen die pomp en die vergassers? ( n T-piece met n baie klein gaatjie in die een pypie, wat terug voer na die tenk toe?

[thys bas]

Boet, ek sal hom bel en uitvind. Dankie

[thys bas]

Deleted

[thys bas]

Boet, op hierdie vliegtuig is daar so iets, ja. Die terugvoerpyp gaan egter nie tenk toe nie, maar na die gasculator om een of ander rede. Dit is 'n CTLS, net die ontwerpers sal weet hoekom. Miskien is daar nie genoeg plek vir nog 'n pyp van onder na bo nie. Ek weet nie presies hoe die brandstofstelsel daar werk nie, maar daar is ook ander snaakse goed soos bv die carb se breatherpypies gaan na die aircleanerbox. Hier is een boks met filter en nie twee soos op ander enjins nie. Dit klink vir my na 'n resep vir moeilikheid.