Message text written by Fred Fillinger
>Where's the water go if the gascolator bowl is filled with water?<
To fill the gascolator with water when most of us are not seeing any water
at all is extremely unlikely. You would either have to ignore water drain
checks for a considerable amount of time or have a sudden large amount of
water introduced to the system to get in that situation.
>A gascolator cannot evacuate in pre-flight all water that's in the
tank unless it's at the very lowest point, which requires it be
mounted in part external to the fuselage. My concern is thus if you
found a good ounce of water in a gascolator, and never a drop before,
would you just drain some more and go flying? Likely a previous bad
load of fuel, with unknown how much is still in the tank that you
can't drain.<
No I wouldn't. Any significant trend change is worth investigating. This is
hopefully an unlikely scenario. At least the Andair gascolator would
prevent this ounce of water from reaching the engine. The water drain
checks serve two purposes. Firstly to drain away very small quantities of
water to prevent buildup and secondly to show that scenarios like you
suggest are not happening. Also the bowl of the gascolator is a much better
trap for debris than the filters as it is less inclined to get blocked as
well as being easier to clean. After about 900 litres of fuel I have yet to
even get any significant debris or water in the bowl.
If you could guarantee to get a drain at the lowest point of the tank then
it is worth having a tank drain as well as the gascolator drain. The
problem is there is no sump on these tanks so the exact position may vary
slightly from tank to tank. The position is a little easier defined on a
monowheel as it will be at the rear of the tank but getting a drain mounted
there is not easy especially retrospectively. If the lowest point of the
tank cannot be tapped then I think the only practical alternative is to
accept that when any water is shaken about during taxy or in flight it
finds its way to the gascolator bowl where it is trapped until the next
water drain check. This all assumes that there is no sudden introduction of
large amounts of water but if there isn't an ability to tap at the lowest
point there is little else you can do. Any water drains taken from the tank
outlet are no better off than the length of pipe between there and the
gascolator as they do not tap from the lowest point of the tank (hence the
unusable fuel at the bottom of the tank). Even if the fuel was taken from
the very bottom of the front of the tank it would easily be possible to
have several ounces of water lurking at the rear of the tank whilst the
aircraft is parked. At least the gascolator water drain checks would show
up this water as some of it would subsequently find its way there after
having been shaken up by taxying and flight.
Nigel Charles
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