Gas Theft Nashua (ASH)

"Matt Whiting" wrote in message ...
Dan Luke wrote:
..... My partner had water problems before installing the flush style gas caps, but none after that unless he pumped
the water in while fueling up. :-) I had a filter on my tank that also trapped water, but he didn't and put some
water in one time.

I think most water that gets to the drains comes in either through a leaky gas cap or was pumped in with the gas. I
don't think condensation is a big issue. If it was, it would likely affect you more in flight than on the ground as
you climb up into cold air with humid warm air in the tanks.

.....
Matt

This has been my experience also, the water mostly comes in from the outside during refueling or a bad filler cap. The
issue with refueling right before a flight is that the water will be in suspension and needs a while to settle out to
the sumps. Is this water in suspension going to cause a problem?

No, Dan, you do NOT have all the numbers on your side. Agreed, you can
calculate the amount of water in a saturated sample, but you cannot do the
simple calculations unless you factor in how many airchanges you get inside
of vented tanks in any given amount of time. I doubt sincerely that you can
even estimate, no less calculate, this factor.

Although if you can get me a government contract to study the issue, I'll be
happy to consider doing the consulting work {;-)

Jim



"Dan Luke" wrote in message
...

"RST Engineering" wrote:

(a) You can go through the math all day long and still not explain why I
have drained the (hangared) 182 after a particularly humid day or two and
get a tablespoon or two of water in the quick drains.

I see: math is false and your charming story is proof. Very convincing. I
have one too: I've been keeping a 172RG with 62-gal. capacity tanks
outdoors in one of the most humid places in the U. S. for six years. I
never top the tanks unless I specifically need to for the next flight.
Only once in that time have I ever had water in a sample, and that was due
to a bad fuel cap gasket.

RST Engineering wrote:
No, Dan, you do NOT have all the numbers on your side. Agreed, you can
calculate the amount of water in a saturated sample, but you cannot do the
simple calculations unless you factor in how many airchanges you get inside
of vented tanks in any given amount of time. I doubt sincerely that you can
even estimate, no less calculate, this factor.

True, but I'll bet it isn't enough to get two quarts of water into 150
tanks! :-)


Although if you can get me a government contract to study the issue, I'll be
happy to consider doing the consulting work {;-)

Better to stick with the electrons and leave the H2O alone. :-)

Matt

"RST Engineering" wrote:

No, Dan, you do NOT have all the numbers on your side. Agreed, you
can calculate the amount of water in a saturated sample, but you
cannot do the simple calculations unless you factor in how many
airchanges you get inside of vented tanks in any given amount of time.
I doubt sincerely that you can even estimate, no less calculate, this
factor.

Actually, the tank respiration is fairly simple to calculate by knowing
the high temp.and the low temp and calculating the quantity that would
need to be added to maintain atmospheric pressure in the tank at the
lower temperature. You will find, I believe, that even in extreme
temperatures the air change would be fractional, even after many days.
Remember also that when the air is most humid, the daily high/low temp.
delta is smallest, thus limiting tank respiration when condensation
conditions are optimum.

Can you to supply any empirical evidence for your claims?

Although if you can get me a government contract to study the issue,
I'll be happy to consider doing the consulting work {;-)

Another poster has mentioned an actual experiment by Cessna that failed
to produce any detectable water due to condensation in the tanks. If
anyone has a link to a description of this experiment, please post it.

--
Dan
C172RG at BFM

"Dan Luke" wrote in message
...

"RST Engineering" wrote:

(a) You can go through the math all day long and still not explain why I
have drained the (hangared) 182 after a particularly humid day or two and
get a tablespoon or two of water in the quick drains.

I see: math is false and your charming story is proof. Very convincing. I
have one too: I've been keeping a 172RG with 62-gal. capacity tanks
outdoors in one of the most humid places in the U. S. for six years. I
never top the tanks unless I specifically need to for the next flight.
Only once in that time have I ever had water in a sample, and that was due
to a bad fuel cap gasket.

So, you've got your little story and I've got mine--so what? I'm the one
with the real numbers on his side.

No Dan, you do not have the numbers on your side. You totally forgot that
the air is not captive inside the fuel tanks. It is free to enter and exit
as the barometric pressure and local wind causes differences in pressure at
the fuel vents. So you may have part of the numbers on your side, you did
not correctly model the problem, and therefore your conclusions are probably
incorrect. Go back and do the problem correctly.

John Severyn
@KLVK

"J. Severyn" wrote:
So you may have part of the numbers on your side, you did not
correctly model the problem, and therefore your conclusions are
probably incorrect. Go back and do the problem correctly.

I believe I adequately showed that the amount of water present in 20
gal. of air under extreme conditions is small, and that the amount that
would actually condense is smaller still. If you believe tank
respiration will substantially increase water condensed out of 20
gallons of air, why don't you provide calculations showing that?

--
Dan
C172RG at BFM

"Dan Luke" wrote in message
...

"J. Severyn" wrote:
So you may have part of the numbers on your side, you did not correctly
model the problem, and therefore your conclusions are probably incorrect.
Go back and do the problem correctly.

I believe I adequately showed that the amount of water present in 20 gal.
of air under extreme conditions is small, and that the amount that would
actually condense is smaller still. If you believe tank respiration will
substantially increase water condensed out of 20 gallons of air, why don't
you provide calculations showing that?

--
Dan
C172RG at BFM

OK. I'll use your own numbers and assume they are correct.

"There's not enough water in 20 gallons of air to matter.

How much water is there? In *extremely* wet conditions (saturated air
at 20 deg. C) there are only 14.7 g/kg of water in the air. A cubic
foot of air at SLP weighs about 34 grams at 20 C. 10 gallons is ~27 cu.
ft., so that gives about 900 g. of air and about 14 g. of water. Not a
problem.

--
Dan
C172RG at BFM"

You did not provide adequate or even convincing evidence that model the
problem.

If the air in the tank is exchanged 10 times over a few weeks (not
unreasonable due to temperature, barometric pressure changes and local
wind), the amount of water starts adding up. The water droplets on the
inside surface will get caught in the fuel as they drip or slowly flow into
the fuel. They will flow to the bottom of the tank and not evaporate as they
are covered with fuel.

In windy conditions, the air can exchange many more than 10 times. Most
aircraft have several fuel vents and many high-wingers connect the top of
the tanks to assure fuel delivery. The multiple vents allow lots of air
exchange if the plane is tied down outside with differences in pressure at
the different vents due to placement and wind.

So let's use your numbers....times 100 or more. 1.4 Kg of water (or more)
is a significant amount.

John Severyn
@KLVK

"J. Severyn" wrote:

You did not provide adequate or even convincing evidence that model
the problem.

If the air in the tank is exchanged 10 times over a few weeks (not
unreasonable due to temperature, barometric pressure changes and local
wind),

"Not unreasonable?" That's what your argument is based on? What is
your criterion for "not unreasonable"?

the amount of water starts adding up. The water droplets on the
inside surface will get caught in the fuel as they drip or slowly flow
into the fuel. They will flow to the bottom of the tank and not
evaporate as they are covered with fuel.

In windy conditions, the air can exchange many more than 10 times.

Do you have any empirical data on which you base this number or did you
just make it up?

Most aircraft have several fuel vents and many high-wingers connect
the top of the tanks to assure fuel delivery. The multiple vents
allow lots of air exchange if the plane is tied down outside with
differences in pressure at the different vents due to placement and
wind.

That is true of my airplane and the three club airplanes with which I am
familiar. All these aircraft are parked outdoors next to a bay on the
Gulf Coast and subjected to continuously damp and frequently windy
conditions. None are routinely topped off after flight--in fact, club
rules proscribe the practice. Persistent presence of water in fuel
samples has not been a problem with any of these aircraft.

So let's use your numbers....times 100 or more. 1.4 Kg of water (or
more) is a significant amount.

Yes, it is. So where is it? Certainly not in the planes I take fuel
samples from.

We have had this discussion before, I believe. I am still waiting for
you to produce any convincing data to make fuel tank
respiration/condensation credible as a serious source of water
contamination in aircraft fuel.

--
Dan
C172RG at BFM

Hank Rausch wrote:

Flew into Nashua last Sunday for business, topped off the tanks right
after setting down. When I came back from business on Thursday, found
the right tank down quite a bit. I was going crazy looking for the
leak and checking the drain for seepage, until the line guy pointed out
that he filled the tank back up exactly 5 gallons--which happens to be
the volume of a standard gas can. He said he'd seen it happen to
another plane on the line, both tanks down 5 gallons.

It was parked pretty much in front of the tower, but it is a low wing
parked in a line of high wings so I guess it made the easiest siphon
target.

I've never given any consideration to gas theft but I think in the
future I will top off right before taking off, as at least thirsty
tanks will make a less attractive target!

Thanks for the warning! When we had avfuel theft problems, it was usually
gear head types obtaining their racing fuel for their riceboxes.

unicate wrote:
It's a gaited airport,

Does it move with a trot, cantor, or gallop?