Running dry?

Nope. I have drained the tanks before and used that measurement to
calibrate the computer. Draining the tank shows the computer to be
correct within 0.1 gallons (1/10 of a gallon). Running the tank dry
once doesn't tell me if I get a new leak but I do also have accurate
fuel gauges. If you fly long trips as often as I do, spend some money
on the gauges and a good, calibrated fuel computer rather than scar the
crap out of your pax.

Robert,

I have drained the tanks before and used that measurement to
calibrate the computer.


In that case, I take back most of what I said. I stand by my statement
that you can apply the technique without scaring anybody, though.

--
Thomas Borchert (EDDH)

On Fri, 19 Aug 2005 09:17:22 +0200, Thomas Borchert
wrote:

Robert,

I know exactely how
much fuel is in each tank.


Nope, you don't. In fact, without running the tanks dry at least once
(or emptying them in the hangar), you have no idea. You know how much
has gone from the tanks if there is no leak. That doesn't tell you at
all how much is left.

Coming back from HTL with full tanks, the gauge on the left main
started down. I didn't know if I had a gauge problem, or the tank was
leaking, or if the quick drain had failed. It was moving fast enough
that if it was correct I was going to be really wing heavy on the
right. As soon as I noticed the gauge going down I switched to the
right tank.

At any rate, I had filled the tank prior to starting out, but I had no
real idea as to how much gas was left. I knew I'd only burn about 4.5
gallons on the way home so I knew what *should* be in there, but not
how much I really had.

I did a precautionary landing at GDW. A check showed no leak and the
level was where it should be. When I fired back up the gauge was
reading properly.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

The primary function of the fuel gauges in most light aircraft is to
indicate when the master switch is on.

Jim



I did a precautionary landing at GDW. A check showed no leak and the
level was where it should be. When I fired back up the gauge was
reading properly.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

"Robert M. Gary" wrote in message
oups.com...
I bought a fuel computer (JPI add-on to my EDM). I know exactely how
much fuel is in each tank.


Assuming the last person who filled it filled it all the way. I find a
discrepancy of about 10 gallons seems to happen depending on how the tanks
are filled.


Michael

Your "K" factor must first be corrected during several top offs. After
that most of the discrepency is caused by various methods of filling to
various levels. Furhter, most gas pumps have cummy metering, and those
that are ripping you off are easy to tell with the JPI FF.

To be most exact, one needs to fill the tanks yourself, from the same
trusted pump. After that the JPI will easily be within .1 gallons of
actual use. Time and time again.

karl

karl gruber wrote:
Your "K" factor must first be corrected during several top offs. After
that most of the discrepency is caused by various methods of filling to
various levels. Furhter, most gas pumps have cummy metering, and those
that are ripping you off are easy to tell with the JPI FF.

Takes three flights, minimum. A fourth can be used to tweak it tightly.

I am concerned about what might happen with the
sediment in these aging fuel bladders as the fuel empties. But, I have
read articles that dispel this myth so perhaps this is a non-issue.

Right. We ran out tanks dry on long overwater flights as standard
practice in the Marines, years ago.

vince norris

On Thu, 18 Aug 2005 09:58:18 -0400, "Peter R."
wrote:

Greg Copeland wrote:

Is this common? How many run their tank(s) dry as part of their fuel
management strategy? If you don't run dry, why not? Aside from the heat
beat skipping which is sure to follow the first couple of times, what's
the down side to this strategy?

I would like to do this just one time for each of the two main tanks in the
Bonanza V35 I fly if for no other reason than to validate the actual
duration and total gallons. However, I have yet to take the time or have
the courage to do so.

As far as disadvantages, I am concerned about what might happen with the
sediment in these aging fuel bladders as the fuel empties. But, I have
read articles that dispel this myth so perhaps this is a non-issue.

I've run every tank on/in the Deb (35-33) dry. Just not at the same
time. At least with the fuel injected engine there is no running
rough. It just quits, but you have plenty of time to reach down and
turn the fuel selector.

This also lets you know if your tanks/bladders are in position and
just how much fuel each tank really holds. Take a ruler and keep
dipping each tank as you fill. Mark the depths as you fill and you
have a calibrated dip-stick.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

On Thu, 18 Aug 2005 09:58:18 -0400, "Peter R."
As far as disadvantages, I am concerned about what might happen with the
sediment in these aging fuel bladders as the fuel empties. But, I have
read articles that dispel this myth so perhaps this is a non-issue.

Maybe this one? http://www.avweb.com/news/columns/182044-1.html

"The Creeping Crud OWT
Then there is the secondary OWT that says something like "But what if some
crud gets sucked into the system from the tank bottom?" Give me a break!
Think about this, for a moment. There are three areas where "crud" might be
a concern. Crud lying on the bottom, crud suspended in the fuel, and crud
floating on the surface. When we fuel the airplane, fuel is injected rather
violently, stirring up the whole tank. When we fly in turbulence, fuel
sloshes rather violently around the tank. Do you really think anything will
be peacefully lying on the bottom, year after year? If it were, why would
running the tank dry stir it up, and if it's that tenacious, how on earth is
running the tank dry going to magically pick it up?

How about suspended crud? It is no more, or less likely to be sucked into
the fuel lines at any fuel level. Floating crud, on the surface? Well,
maybe, but can you name me something that will do that? And if there is,
well, how much of it will you allow, before you rip the tank out for
"cleaning," or how WILL you get it out, someday? Just how, and when, will
you identify it, detect it, and get rid of it? And, how much fuel do you
want as a "buffer" below the floating crud, to keep from sucking it in? In
fact, if there is a little something floating on the surface, I WANT it to
be sucked into the fuel lines, preferably a little at a time, so that the
strainers and filters can catch it, and alert me that something is going on
in there. The likelihood of there being enough to cause a problem is remote,
at best, and if running a tank dry will pick up a little crud, then running
a tank dry often is a very good thing, because you'll catch it a little at a
time, and drain it out the strainer.

Of course, if you keep the tank full most of the time, and the cap on, and
drain the sumps often, there isn't any way for crud to get into, or stay in
the tank in the first place."