"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}