Fuel selector question

"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote in message
...
Frankly, on a C-172 I can't think of any reason either.

http://www.caa.is/datadir/bsdata/img...s/72-07-02.pdf

Karl

"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote in message
...

On the C-402 for example, you had to burn a good 30 minutes on the
outboards (which were its mains) before you could switch to the inboards.
When you switched to the inboards, the fuel actually went from the
inboards to the outboards to the engine. If you didn't make room first by
burning the outboards first, the fuel pumped from the inboards would just
be pushed through the overflow valves on the outboard tanks and then you
get to sprinkle the landscape with expensive avgas.

You got that partially right. The aux tanks each have their own electric
fuel pump that pushes the fuel throught the selector valve and on to the
engine driven fuel pump. Excess fuel from the engine driven fuel pump is
routed back to the main (tip) tanks. The reason for running on the tip
tanks first for 60 (or 90 for the large aux tanks) minutes is to make room
for this bypass fuel.

--

*H. Allen Smith*
WACO - We are all here, because we are not all there.

On Oct 6, 12:47 am, es330td wrote:
Sorry if this is dumb (I am only at 8.3 hours toward my PPL)...

In the email I got from AOPA ePilot training tips today there is a
discussion of fuel starvation that makes regular mention of the fuel
selector switch. All my flying is done in a CE172 and the first and
last time I worry about the switch is during pre-flight when I confirm
that it is on both. I fly on both and never fly any other way and to
be honest, outside of gravity flow issues when parked on an incline I
cannot think of why one would want to select one tank at a time vs
both.

If you ever get to a situation where you are worried about fuel, you
switch to one tank and start your watch, when that tank runs dry
(engine splutters) you will have a very good idea of how much flying
time you have left. This knowlege will enable you to decide if your
chosen alternate airfield is in reach or if you neeed to start your
precautionary landing procedures (looking for a paddock etc.)

Cheers

On Oct 6, 4:25 am, "karl gruber" wrote:
On many Cessna 172s you are REQUIRED to run on either left or right (not
both) above 5000'

Karlhttp://www.caa.is/datadir/bsdata/img/adnotes/72-07-02.pdf


Many cessna 172's? How many were not modified -I've not seen the
required placard...

Cheers

Some times after some maneuvers.. or continuous pattern work with not that
great coordination.. you may find one tank (wing) heavier than the other
because the fuel is unbalanced. select the heavier (fuller) tank for a few
minutes and monitor to rebalance, then back to "both".

Of course.. training to select one tank or the other for single tank
operations, prepares one for flying other aircraft.

BT


"es330td" wrote in message
ups.com...
On Oct 5, 9:03 am, wrote:
On Oct 5, 2:47 pm, es330td wrote:

Sorry if this is dumb (I am only at 8.3 hours toward my PPL)...

In the email I got from AOPA ePilot training tips today there is a
discussion of fuel starvation that makes regular mention of the fuel
selector switch. All my flying is done in a CE172 and the first and
last time I worry about the switch is during pre-flight when I confirm
that it is on both. I fly on both and never fly any other way and to
be honest, outside of gravity flow issues when parked on an incline I
cannot think of why one would want to select one tank at a time vs
both.

The POH will answer that.

-Kees

I bought one two days ago. I should finish reading it this weekend.
Thanks.

On Oct 5, 7:47 am, es330td wrote:
Sorry if this is dumb (I am only at 8.3 hours toward my PPL)...

In the email I got from AOPA ePilot training tips today there is a
discussion of fuel starvation that makes regular mention of the fuel
selector switch. All my flying is done in a CE172 and the first and
last time I worry about the switch is during pre-flight when I confirm
that it is on both. I fly on both and never fly any other way and to
be honest, outside of gravity flow issues when parked on an incline I
cannot think of why one would want to select one tank at a time vs
both.

If you are running on "BOTH" and there is an obstruction in a fuel
line, fuel could feed only from the other tank and you might find
yourself with fuel starvation long before you expect it. Changing
between left and right on a regular basis may let you discover such a
problem before it's an emergency. A close watch on fuel gauges and
being sensitive to heavy wing helps too.
--
Gene Seibel
Gene & Sue's Aeroplanes - http://pad39a.com/gene/planes.html
Because we fly, we envy no one.

On Fri, 05 Oct 2007 18:38:09 -0000, wrote:

On Oct 6, 4:25 am, "karl gruber" wrote:
On many Cessna 172s you are REQUIRED to run on either left or right (not
both) above 5000'

Karlhttp://www.caa.is/datadir/bsdata/img/adnotes/72-07-02.pdf


Many cessna 172's? How many were not modified -I've not seen the
required placard...

The modification was to add a new vent line. I don't know any on the
flight lines I have access to that weren't done. They also all
complied with AD79-10-14R1 (new vented fuel caps) at the same time.

"Allen" wrote in message
. ..


"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote in message
...

On the C-402 for example, you had to burn a good 30 minutes on the
outboards (which were its mains) before you could switch to the inboards.
When you switched to the inboards, the fuel actually went from the
inboards to the outboards to the engine. If you didn't make room first
by burning the outboards first, the fuel pumped from the inboards would
just be pushed through the overflow valves on the outboard tanks and then
you get to sprinkle the landscape with expensive avgas.

You got that partially right. The aux tanks each have their own electric
fuel pump that pushes the fuel throught the selector valve and on to the
engine driven fuel pump. Excess fuel from the engine driven fuel pump is
routed back to the main (tip) tanks. The reason for running on the tip
tanks first for 60 (or 90 for the large aux tanks) minutes is to make room
for this bypass fuel.

--

*H. Allen Smith*
WACO - We are all here, because we are not all there.


Correct for the AUX tanks. However, the optional locker tanks function
just like Mortimer said.

Al G

On Oct 5, 12:09 pm, Gene Seibel wrote:
On Oct 5, 7:47 am, es330td wrote:

If you are running on "BOTH" and there is an obstruction in a fuel
line, fuel could feed only from the other tank and you might find
yourself with fuel starvation long before you expect it. Changing
between left and right on a regular basis may let you discover such a
problem before it's an emergency. A close watch on fuel gauges and
being sensitive to heavy wing helps too.

My Mooney doesn't have a both. However, its nice to know that if I
ever did run out of gas, I could always switch to the other tank and
having something left. If you run out in a C-172 on "both" you're
done.

-Robert

Allen wrote:
"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote in message
...

On the C-402 for example, you had to burn a good 30 minutes on the
outboards (which were its mains) before you could switch to the inboards.
When you switched to the inboards, the fuel actually went from the
inboards to the outboards to the engine. If you didn't make room first by
burning the outboards first, the fuel pumped from the inboards would just
be pushed through the overflow valves on the outboard tanks and then you
get to sprinkle the landscape with expensive avgas.

You got that partially right. The aux tanks each have their own electric
fuel pump that pushes the fuel throught the selector valve and on to the
engine driven fuel pump. Excess fuel from the engine driven fuel pump is
routed back to the main (tip) tanks. The reason for running on the tip
tanks first for 60 (or 90 for the large aux tanks) minutes is to make room
for this bypass fuel.


Oops... it's been a while.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com