From: marv@lancair.net
Subject: Re: [LML] Re: Fuel tank camera for inspection of Lancair fuel
 tanks
To: <lml@lancaironline.net>
Date: Fri, 23 Feb 2007 15:24:40 -0500
Message-ID: <web-1858491@logan.com>
In-Reply-To: <bf7.10461880.3310a294@aol.com>
References: <bf7.10461880.3310a294@aol.com>
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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