We’ve got a bit of a mystery. Our high wing a/c has a left and a right 45 liter wing tank. These are connected via a four way Andair fuel valve on which you can select left or right or both, then off. The a/c stands on ground with a one or rwo degree gradient that slopes towards the left wing tank.
We usually select the valve to ‘both’. After landing on a level runway and travelling less than a hundred level yards to our parking place, the engine is switched off and immediately the fuel valve moved to ‘off’.
When, next day or the day after we return to the a/c and dip the tanks, the left wing tank always contains at least double the amount in the right tank.
Could it be that fuel is seeping past the ‘off’ position on the Andair? We don’t think the fuel bandits are back
because the amount of fuel left tallies with that that we estimated was used. Anyone got any ideas please?
If you have could you make it sound complicated, if it is something simple I don’t think that I could stand the shame and embarrassment !
By: mike currill - 17th June 2013 at 09:14
I meant to add that the problem is no limited to high wing aircraft. I have seen the same thing happen on a Seneca. Mind you, that was because whoever refueld it had left the cross feed **** open. I think basically it is a case of making sure that you understand exactly how your particular fuel **** works. Not a problem I’m likely to be bothered by as the EV-97 has only one tank and a fuel **** that is either on or off.
By: mike currill - 10th June 2013 at 13:48
IThe forumites rise to the occasion again. If you have a question there’s a good chance someone on here will be able to answer it.
By: The Blue Max - 9th June 2013 at 23:24
Glad to be of service 🙂
By: John Green - 8th June 2013 at 19:40
Blue Max
Went to the a/c to-day. Checked the fuel levels. Both more or less equal ! You were right. Thank you.
By: John Green - 7th June 2013 at 17:12
I’ll be at the a/c either tomorrow Sat. or Sunday.
By: The Blue Max - 6th June 2013 at 22:32
I’ll be interested to hear the result 🙂
By: John Green - 5th June 2013 at 22:52
Doesn’t leak like one – I’m pleased to write !
I flew to-day and left the a/c with the Andair switched to the left tank – in line with Blue Max’s suggestion.
By: BlueRobin - 5th June 2013 at 12:25
A proper aerial Land Rover then 🙂
By: John Green - 4th June 2013 at 20:57
Chaps, many thanks for your replies. I think that Blue Max might have the answer in that OFF cuts the supply to the engine but retains continuity of supply to both tanks.
Tony.
It’s a Zenair 701 Group A. The filler caps are both vented and have been checked clear. I think that the next thing to do is turn the a/c around so where the left wing is the right will be eg. on the gradient side. I’ve got a notion that the same drainage will occur but this time to the right wing tank. We’ll see.
A/c weight is the same – nothing additional. Tyre pressures are checked at least once a week – tundra tyres at 20psi each.
By: BlueRobin - 4th June 2013 at 10:36
The Maule used to do the same. Weed a lot out of one side too. IIRC has to select the LEFT tank when parked.
By: TonyT - 3rd June 2013 at 23:09
John I cannot remember what you have, Cessna have a vent line linking both tanks that runs just behind the front spar, the reason being early Cessna’s only used to have a vented cap on one side, the tanks were interlinked to ensure internal pressure equalisation, otherwise the tanks would collapse as the engine drew fuel…. Several actually happened due to the vented caps getting mixed up and put on the wrong side, the tanks then collapsed, Cessna’s fix was to change the caps to having vented ones on both sides, however the tanks are still vent balanced as I said with an interlinking pipe, slight slope and it transfers…. the more it transfers the more the wing drops the more fuel is transferred.
Anything changed, extra weight inside? Soft tyre?
By: The Blue Max - 3rd June 2013 at 21:59
I suspect that in the OFF position the two tanks are conected. OFF only cut fuel to the engine side and more than likely the way the valve works in the OFF position the fuel can flow between the tanks. Thus if there is a slight gradient the fuel can flow from one tank to another. If the valve was an OFF, Left and Right selection without the both it would not be able to do it.
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June 3, 2013 at 9:46 pm