REFLECTOR: fuel unbalanced

[vance atkinson]

I developed the sump system for the Cozys of which I have.  My original 
system was std LEZ (one left and one right tank...selector to choose 
which one)  When I retrofitted the sump tank, it had no vents to it.  
Just the L/R main tanks with their respective separate vents and each 
tank fed the sump.

I discovered  that you can have/uneven feeding to the sump due to the 
alignment of the vents/ of each tank in respect to the relative 
airstream.  The vent material tubing is versatube and easily bent.  Just 
one degree on the angle of the tube can make a difference when one tank 
stops feeding the sump and the other one takes over.

If your vent tubes are close together and look like identical angles, 
there may be a slipstream protuberance  further upstream.  I have one on 
each side of the plane under each fuel strake.

Something to check (along with all the rest) if you have an uneven 
feeding event.

I am also a glider instructor and the yaw string is the only cheap way 
of determining if your plane flies crooked !  Try it, its simple and 
easy, just make sure you have a center line  marked on your fuselage and 
a spot on the canopy marked.... (tape works great)

Vance Atkinson
EAA Tech and Flt Advisor
COZY N43CZ
VEZ N3LV


> Richard,
> This is just a "me too," to what has already been said.  I have an 
> XL with the Atkinson clear fuel sight gauges in the cabin.  I used 
> to check only the RH one in flight and see that it was about right, 
> and never compared it closely to the other which is difficult to see 
> for me due to have to crane my neck around or even half climb out of 
> the pilot seat.  I have a forward facing fuel vent tube out the belly, 
> with a small whole drilled on the back face for an alternate orifice 
> in the chance of ice.  Well I got into a brief but heavy transit thru 
> about 1000 to 1500 feet of cloud in central Penn that surprised me, 
> and it was slow to come off since once on top the outside air was too 
> cold.  So I began to fret that my vent tube was liked iced some.  So I 
> looked at both my sight gauges and they were an inch (aprox 5 gal) or 
> more apart and it scared the hell out of me.  Since then I have 
> learned that they do sort of rachet back and forth and do not come 
> down exactly even.  The flight was uneventful.
>
> John Abraham's yaw string idea is ancient, and quick and easy to do.  
> Leave it on there for a whole series of flights.   A small hunk of 
> masking tape and a foot or so of knitting yarn works great.  If you 
> have some one with you, you can try scribing your yaw angle if it is 
> off any w/ a water magic marker so you have a ref point for any 
> changes or experiments you might try.  Good luck, but also be sure 
> your vent system works right or it could completely stop your fuel 
> feed.  It's dirt simple, but vital...I'm sure you know that.
>
> Terry

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