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Posted for REHBINC@aol.com:
In a message dated 2/23/2007 1:11:00 PM Eastern Standard Time,
marv@lancair.net writes:
Posted for Matt Reeves :
You guys have me paranoid now. Are you saying it's a very real possiblity
for static from flight to cause a wing to blow up? If a guy blew up from
waxing his Lancair, how safe it is to actually fly in an environment that
creates static? My airplane is e-glass and honeycomb, not carbon fiber so
there really is no way to ground the wings.
Some expert opinions?
Matt,
Assuming: 1. the fuel in your wing is gasoline, 2. there is still some amount
of liquid present and 3. you haven't rapidly drained the tank in the last
hour (i.e., much faster than a 300 hp engine uses fuel) or found some other
way
to get a lot of fresh air inside (i.e., opened a big hole in the side or
discharged an air line inside ) then the atmosphere inside will not be
flammable.
The fuel/air ratio will be far too rich. You may wax your airplane all day
long
without any worry of it causing the fuel tank to explode. Static from flight
won't do it either. You could flick your bic inside if you wanted to, but
even
your lighter would not light.
Nearly all gasoline tanks that explode, do so in the movies. In real life it
is very rare. Empty tanks are the most dangerous since the lack of liquid
fuel
leaves no way of keeping the fuel air ratio above the rich limit. However,
there is usually enough vapor to mix with the fresh air and reach the
flammable
range in some area of an empty tank. This is when it becomes explosive.
Weeping fuel leaks into adjacent areas are also problematic as the fuel leak
rate may not be enough to maintain the compartment fuel rich.
If you have emptied your tank to do an internal camera inspection, I would
suggest inerting the tank space with CO2 or other inert gas before inserting
any
potential ignition source into the tank. It would also be advisable to have a
calibrated gas meter on hand to be certain that the tank atmosphere is
nonflammable before and during your inspection.
If the fuel is methanol, assume that the tank is always explosible unless it
has been inerted and tested. Under normal sea level conditions, the vapor
pressure of methanol is only sufficient to bring the head space into the
flammable
range. It will not reach a fuel rich condition.
Diesel and Jet fuels have insufficient vapor pressure at normal sea level
conditions and so their tank head spaces SHOULD be safe. However,
contamination
with gasoline (event slight contamination) can result in an explosive
condition, so be careful. Also, when warm sea level fuel is carried up
several thousand
feet, the reduction in air pressure results in diesel and jet fuel head space
feul/air ratios entering the flammable range. Pay attention turbine builders
and remember TWA 800.
Except for the TWA 800 scenario, I have seen the result of each of the above
hazards and have worked to find their root causes. The results can be very
impressive.
Rob
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