Fuel Selector Valve

For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?

"Jay" wrote in message om...
For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?

Because there's a fuel pump involved. If one tank goes dry, the pump
sucks air. Easy experiment. Grab two straws. Stick one in a glass of
water and let the other one stay outside the glass and try to drink from
them.

There are a few low wing planes with "BOTH" positions on the selector, but
they drain to a common tank and the pump draws singly from there.

In article ,
(Jay) writes:


For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?



In theory, Yes it would be easier to feed off both simultaniously but the
reality is that it wouldn't happen that way. It will always pull from the tank
giving the least resistance and, when that tank ran out of fuel, it would
continue to try and pull from it until you contacted the ground. The only way
to guarantee a fairly equal use from both wings is to switch the lead from the
tanks on a regular basis.

In addition, the balanced use of fuel from each tank will help keep the plane
from having a heavy wing.
Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

I'll second that!!!

I flew a Beech Skipper (yea, I know but I was young.) that used a ON-Off
selector instead of selecting a wing tank. Right side tank always went low
first (1/4 tank) before the left tank would show 3/4's of a tank left.

Mechanic was top notch, but with all his efforts (short of installing a
non-certified part) it only got marginally better. Even flying with the left
wing high did not improve things.

Bart
--
Bart D. Hull

Tempe, Arizona

Check http://www.inficad.com/~bdhull/engine.html
for my Subaru Engine Conversion
Check http://www.inficad.com/~bdhull/fuselage.html
for Tango II I'm building.

RobertR237 wrote:

In article ,
(Jay) writes:


For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?




In theory, Yes it would be easier to feed off both simultaniously but the
reality is that it wouldn't happen that way. It will always pull from the tank
giving the least resistance and, when that tank ran out of fuel, it would
continue to try and pull from it until you contacted the ground. The only way
to guarantee a fairly equal use from both wings is to switch the lead from the
tanks on a regular basis.

In addition, the balanced use of fuel from each tank will help keep the plane
from having a heavy wing.
Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

"Ron Natalie" wrote:


For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?

Because there's a fuel pump involved. If one tank goes dry, the pump
sucks air. Easy experiment. Grab two straws. Stick one in a glass of
water and let the other one stay outside the glass and try to drink from
them.

There are a few low wing planes with "BOTH" positions on the selector, but
they drain to a common tank and the pump draws singly from there.
++++++++++++++++++++++++++++++++++

Not true of the Ercoupe I once owned.

Header tank was common to both wing tanks.

Fuel was pumped from BOTH wing tanks
to that common tank and then gravity fed
to the engine.

When the common tank was full, the excess
was gravity fed to the left tank. Some other
Coupes returned fuel to the right tank.

Both tanks were connected together,
so fuel would balance out... eventually.


Barnyard BOb --

Yes. My Velocity has a 5 gal header tank hard-plumbed to the two wing
tanks. The two wing tanks self-level within a gallon or two during
normal flight (and sitting in the hanger). A pick-up tube in the
header tank goes off to the fuel system thru one on/off valve that
remains always on. Can't get much simpler than that.

Sid Knox
Velocity N199RS
Starduster N666SK
KR2 N24TC
W7QJQ

For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?