Fuel selector question

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.

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

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.

wrote in message
ups.com...
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.


Wise ass.

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.

All aircraft fuel systems aren't as simple as they are in the 172. All
Aircraft can't use gravity feed either.

Let's take for example the little 601XL I'm building. It is low wing and the
fuel pumps move the fuel from the wing tanks to the engine. No as an
experiment to see what would happen if there were a both setting on the fuel
selector take a glass of water and two drinking straws. Put on of the straws
in the glass and hold the other out side the glass. Put both straws in your
mouth and suck.

On Oct 5, 3:21 pm, "Maxwell" wrote:
wrote in message

ups.com...

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.

Wise ass.

Thank you.

Bob Moore wrote:
Gig 601XL Builder wrote
Let's take for example the little 601XL I'm building. It is low wing
and the fuel pumps move the fuel from the wing tanks to the engine.
No as an experiment to see what would happen if there were a both
setting on the fuel selector take a glass of water and two drinking
straws. Put on of the straws in the glass and hold the other out
side the glass. Put both straws in your mouth and suck.

Doesn't have to work like that. I have a lot of time instructing in
YAK-52s.
Low wing, and only one fuel ON/OFF valve. Both wing tanks feed to a
central sump which then feeds a header tank via an engine driven fuel
pump. With both tanks "straws" feeding the central sump, which is
heavier, 100LL or air? Yep, even with one tank empty, the heavier fuel
in the other tank keeps the sump full. I pretty sure that there are
some flapper valves in the sump to prevent the fuel from running into
the low wing in a turn.

Bob Moore

I didn't say it had to work like that. I was showing the OP an example of
one fuel system that would not work safely with a BOTH position fuel
selector.

es330td wrote:
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.

Frankly, on a C-172 I can't think of any reason either. But different aircraft
have different systems. As you move up the Cessna line you will find aircraft
that don't offer the "both" option. None of the Pipers do. In fact, I can't
think of a general aviation low wing aircraft I ever flew that offered "both" as
an option. So in that situation you:

1. Take off and land on the fullest tank.

2. Switch tanks every 30 minutes to keep the aircraft from becoming heavy on
one side.

3. If you have to manage both inboard and outboard tanks, I prefer to burn the
outboards first so that the remaining fuel has less effect on balance. Of
course, some aircraft require specific handling.

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.

4. Bottom line: read the manual and follow their directions.


--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

On Fri, 5 Oct 2007 08:21:50 -0500, "Maxwell"
wrote:


The POH will answer that.


Wise ass.


What's up with that?

Getting a new pilot into the habit of going to the POH _first_, is a
bad thing? G

On many Cessna 172s you are REQUIRED to run on either left or right (not
both) above 5000'

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


"es330td" wrote in message
ups.com...
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.