faith in the fuel delivery infrastructure

I'll probably need an airport tour to answer this to my satisfaction, but I
thought it merited a discussion here anyway.

It seems pretty standard that, after an airplane is refueled, you wait 10-15
minutes and resample the fuel to check for contaminants (water). I recently
witnessed a situation where the fuel was checked during preflight, but not
after refueling. The reason given was that at this particular airport, the
fuel supply is replenished/recycled daily, if not more, and so there isn't
time for water, or perhaps *enough* water, to collect in the storage tanks
and end up in an aircraft's fuel tanks.

I'm not convinced. Work experience with mechanical things tells me that
mechanical things malfunction. Could water get into the fuel truck's tank?
Could water get into the storage tank? Could water get into the tanker
bringing fuel to the airport? Could there be water in the fuel at the depot?
Etc...

I really don't know enough to answer this. It seems that the most likely
causes of water contamination would be condensation in an airplane's fuel
tank, or a leak in the airport's fuel storage tank. If the fuel doesn't sit
in either for long, then that probably would reduce the risk to near zero. I
would imagine that there's some other failsafes in place to prevent water
from getting to the aircraft - perhaps the refueling trucks are individually
checked before they are sent out. Still, if water gets into the system at
ANY point, seems it's going to wind up in SOMEBODY's gas tank, no matter how
often the supply is recycled?

While we're at it, are these types of fuel checks standard procedure for ALL
aircraft, or just the little piston-powered ones?

Water can get into the system at any point, as you suggest.

As for waiting 10 to 15 minutes before sampling the fuel, why? Try this
experiment: put some water and some fuel in a jar. Shake it up, and time how
long it takes for the water to settle out.

"Chris Hoffmann" wrote in message ...
I'll probably need an airport tour to answer this to my satisfaction, but I
thought it merited a discussion here anyway.

It seems pretty standard that, after an airplane is refueled, you wait 10-15
minutes and resample the fuel to check for contaminants (water). I recently
witnessed a situation where the fuel was checked during preflight, but not
after refueling. The reason given was that at this particular airport, the
fuel supply is replenished/recycled daily, if not more, and so there isn't
time for water, or perhaps *enough* water, to collect in the storage tanks
and end up in an aircraft's fuel tanks.

It could. The truck's tank should be sampled and checked for water
just like the airplane though. It is a good idea to check the fuel
after fueling (I usually skip it during the pre-flight if I'm going to
go get fuel).
-Robert

"C J Campbell" wrote in message
...
Water can get into the system at any point, as you suggest.

As for waiting 10 to 15 minutes before sampling the fuel, why? Try this
experiment: put some water and some fuel in a jar. Shake it up, and time
how
long it takes for the water to settle out.

10 to 15 minutes might be overly generous, but your experiment doesn't
really duplicate the conditions within an aviation gas tank.

Some are lined with rubber bladders, that can get small wrinkles (or
sometimes large wrinkles, which is really bad) that hinder the flow of water
toward the drains. Others have part of the wing structure inside the tank,
with holes drilled at the bottom, that impede that flow. In ALL
wing-mounted tanks, water can be quite distant laterally from the drain, and
it will take the water a lot longer to flow toward the drain along the
bottom than it would for water to be pulled by gravity straight down in a
jar.

In a jar, water will settle in a matter of tens of seconds, even if shaken
vigorously (much quicker if it's not). But in a fuel tank, it can easily
take several minutes.

So: always test your fuel (besides, you're not just looking for water).
Always give the fuel some time to rest before checking (at least a few
minutes). If you find ANY water, gently rock the wings to encourage water
to get past any obstacles and get it into motion toward the drain, and wait
a longer period of time just to make sure, and then check again. Repeat
until you have no water.

Pete

(water). I recently witnessed a situation where the fuel was checked
during preflight, but not after refueling.

How then would one know if the tanks were filled with the wrong type of
fuel?

"Chris Hoffmann" wrote in message ...
snip Good questions
It seems that the most likely causes of water contamination would be
condensation in an airplane's fuel tank...
Snip Excellent thoughts.
I once questioned a tank truck driver who was siphoning the storage
tank of an automobile service station. He told me he was removing dirt
and water from the bottom of the station's tank before he refilled it.
He added that his Brand's reputation was at stake so their trucks were
'clean' but they wanted to be sure the station's tanks were also
'clean', as too often they were not and he had to do it himself, by
Brand Company's Policy. One might suspect that such might be the case
for some avgas stations, but I have no evidence or testimony that such
may occur, currently. Your deduction of a'cft fuel tank condensation,
as a major factor, is right on, from my personal experience. FWIW.
While stationed on the Mississippi Gulf Coast, between Gulfport {G}
and Pasagoula {P}, I had an old Taylor E2 Cub that was primarily flown
to keep my coordination sharp when I had no flying duty. It had an
A-40-4 single ignition engine equipped with a settling glass, also
used on some automobiles. It was easily accessible on the right side
of the engine compartment, between the tank and carb. Fuel entered a
glass sump where water and dirt particles settled to the bottom of the
sump where they were easily seen. Ambient air was always very humid on
the coast and the diurnal temps varied enough so that condensation
always had to be considered as in the a'cft's fuel tank, at first
daily startup. Usually, there was a small amount {less than a
teaspoonful} of water in the glass {which would hold about an ounce
safely} to be dumped, but it appeared only 'after' initial warm up. No
water contamination from refueling tanks at either the P or G airports
was ever found but there was always a small amount in the bottom of
the tank after the engine had cooled and it had been sitting for
several hours or overnight. Ergo, condensation of water, from the
amount of humid ambient air in the tank and tank temps, were very
important considerations, but all contaminants had to flow from the
tank to the settling glass before they were visible and could be
dumped. In this a'cft, a preflight inspection fails to detect
contaminants that may still be in the tank, unlike those that have
drains for each tank that can be sampled or used to purge water/dirt
during a preflight. Air contamination of a fuel line sounds
ridiculous. I once started a forced landing when the E2's 40HP engine
began quitting intermittently with insufficient power output to
sustain level flight. There was no place to land except a large
orchard with soft ground and insufficient space between the trees for
the wings. I had been warned that single ignition systems could cause
trouble from a fouled plug, but this engine was not 'missing on one'
it was 'quitting' on all four, simultaneously. About fifty feet above
the tree tops I thought it sounded more like fuel starvation and
started pumping the priming pump, constantly. This small amount of
additional fuel kept the engine running more often and was sufficient
to mush to the P airport without losing more altitude. Post landing
inspection showed the glass sump was not screwed tightly against it's
cork gasket. I recalled that the sump had been dumped for me by a
buddy. Evidently, he had not torqued it sufficiently to prevent it's
loosening, allowing air leakage and a leaner mixture that would not
combust. It was obvious that hereafter, I should do it myself or have
a qualified person, familar with the E2, do it for me, but only if
absolutely necessary. As you know, currently there are more
complicated and efficacious water/dirt separators available for both
gasoline and diesel engines but they may be too large for some light
a'cft's reasonable installation. {Finis}

"John Harlow" wrote in message
...
(water). I recently witnessed a situation where the fuel was checked
during preflight, but not after refueling.

How then would one know if the tanks were filled with the wrong type of
fuel?

.....Now that's an even better question. Thank you!

"Peter Duniho" wrote in message
...
"C J Campbell" wrote in message
...
Water can get into the system at any point, as you suggest.

As for waiting 10 to 15 minutes before sampling the fuel, why? Try this
experiment: put some water and some fuel in a jar. Shake it up, and time
how
long it takes for the water to settle out.

10 to 15 minutes might be overly generous, but your experiment doesn't
really duplicate the conditions within an aviation gas tank.

Some are lined with rubber bladders, that can get small wrinkles (or
sometimes large wrinkles, which is really bad) that hinder the flow of
water
toward the drains. Others have part of the wing structure inside the
tank,
with holes drilled at the bottom, that impede that flow. In ALL
wing-mounted tanks, water can be quite distant laterally from the drain,
and
it will take the water a lot longer to flow toward the drain along the
bottom than it would for water to be pulled by gravity straight down in a
jar.


Then why wouldn't you rock the wings to start out with? Make sure all the
water flows to the sump right away.

"C J Campbell" wrote in message
...
Then why wouldn't you rock the wings to start out with? Make sure all the
water flows to the sump right away.

I never suggested you wouldn't. Not sure how you got the idea that I had.

How then would one know if the tanks were filled with the wrong type
of fuel?

checking the fuel receipt is always a good start


--
kat
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