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FUEL COCKS


johnm
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Irrespective of what the operation manual says ?? - with the 2 fuel cocks in a high wing Tecnam, what happens when the fuel contents get real low ?

 

If you fly for say 2 1/2 hours, fuel consumption will be virtually from one tank - 1/4 full - whereas the other tank can still be say 3/4 full.

 

The fuel gauges also seem to read more fuel used than what is actually used - safety no doubt

 

So what say you had 2 1/8 full tanks (say you had to ...... or wanted to keep flying) - I'd bet the fuel gauges would be reading 'all but zero' - but with 25 litres you could fly for another 1.50 hours

 

Will all the fuel be consumed from both tanks before she 'splutters' - with both fuel cocks on ?

 

Has anyone had some 'real time' experience managing fuel with 'all but zero' fuel gauges ?

 

 

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Even fuel indications.

 

johnm, I suspect that the differing readings are caused by flying one wing low OR ball displaced from centre. (only has to be a little bit). IF this is not the case, as for example if the venting produces uneven pressure I would try to maintain quantities even, by turning the low reading tank OFF, if one tank is getting near empty , as an empty tank can introduce air into the system, sometimes. Do this at a good height just in case the engine falters. Good idea to return to 2 tanks prior to making an approach, unless one is empty, or almost so. Double-check your selection always when operating FUEL selectors and monitor your engine for 3 or 4 minutes after making a change. Nev..

 

 

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The usual reason for one tank using more than the other is by flying in unbalanced flight.

 

If you do it deliberately, and the light is hitting the AC at the right angle, you can see the plume of fuel venting overboard.

 

Now you know how those fuel stains get on the flaps!!

 

Moral of the story is with a Tecnam, keep the thing in balanced flight all the time or you lose fuel.

 

Ben

 

 

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Guest aircraft1

Unbalanced fuel and flying etc

 

Dont forget the fuel return line in all the Rotax install's. It is not just flying unbalanced that puts more fuel in one tank than the other. This should all be part of your training etc ??

 

 

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Hi there Johnm

 

With the Tecnam you need to turn off the right fuel tap every so often, as required, so fuel is drawn from the left tank only until the imbalance is corrected, and then reopen both taps. On a long cross country you need to do this every 20 minutes or so.

 

The reason for this is simple....the fuel return circuit (to prevent vapour lock and hot fuel) is to the left tank.

 

Now if there were 2 return lines...one left and one right, then this would probably solve the problem??

 

Can't help you with the other part of your question...I never flight plan with margins below 25 - 30 litres....best to ask Bruce Stark of Tecnam Australia for an accurate answer on that one.

 

Cheers

 

 

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Guest bateo

I too have this occur to me in flight, and like Tecnamman, I switch my right tank off every 20 minutes or so to re-balance the quantity in tanks, I too have experienced ( not pushing my luck) but can get an extra hour endurance on a tank that says empty! I though have the long range tanks, whether this makes any difference I am not sure...

 

 

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Guest aircraft1

It will make a difference with the long range tanks.

 

You will be further away from where you took off from when you run out of fuel !

 

The best way is to not trust the gauge but trust your own experience, if you have experience of using say 15 lph then start with full tanks and calculate your consumption based on time. A gauge can be VERY wrong, but fuel consumption and time cant be wrong especially when you know how much fuel you atarted with.

 

See you next Saturday week !

 

 

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Guest Crezzi
... but fuel consumption and time cant be wrong especially when you know how much fuel you atarted with.

Not always true - if fuel is leaking or venting your "consumption" would be much higher than the normal burn rate you are planning on.

 

An Airbus (IIRC) on a trans atlantic flight made that mistake after a fuel pipe chaffed through - they had to dead stick into the Azores after gliding a considerable distance

 

Cheers

 

John

 

 

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Guest bateo

A bit of a different situation, but is relevant to fuel in the Tecnam High wing.

 

I was told from a RA-Aus representative that I should look into moving my fuel drain from the engine bay, into 2 separate draining valves in the wings.. Apparently, The fuel drain only obtains some of the fuel sample not reaching from the all points of the tank (must be located in a high spot or something), so when fuel is low and moisture may have occured in the fuel, that it could possibly go undetected.

 

I am not sure if this true, maybe just in the earlier models... Although I have never detected water in the tanks of the Tecnam, it still is a thought in the back of my mind.

 

 

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summary ?

 

I know that if you keep the black tooth in the middle of the happy face (slip indicator ?) then flight is balanced ......

 

Even if I lie - the question remains the same - what happens towards the end of fuel supply ? To say you would n't use your 45 minute fuel reserve (or whatever reserve you are comfortable with) is something you can't say. Circumstances may make you want, or have to, keep flying and consume what fuel (or reserve) you have.

 

True, a record of actual flight time helps

 

I am not talking about airmanship or fuel stains on flaps

 

I'll try and find the technical answer and post it (the answer might be that fuel exhastion of both tanks occurs at the same time - towards the end of their volume they evenly empty at the same time 032_juggle.gif.8567b0317161503e804f8a74227fc1dc.gif)

 

 

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