Re: Fuel Tank Safety

From:         "Brian A. Reynolds" <bareynol@cca.rockwell.com>
Organization: Rockwell Avionics - Collins
Date:         Sat, 29 Mar 1997 06:32:31 GMT
References:   1
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Malcolm Hopkins wrote:
> 
> Some years ago I read an article about a product (of U.S.A. origin I
> think) called "EXPLOSAFE" that had a very impressive performance and
> took up a similar volume as the foam , if remember correctly. It was
> also featured in a television program showing its potential in motor
> racing and marine marine environments.
> 
> Explosafe was a like expanded aluminium sheet albeit extremely thin,
> it was folded back and forth to fill up a fuel tank (during
> construction). It was also able to be retrofitted to existing fuel
> tanks by cutting a suitable access hole. I believe it work through
> rapid heat dissipation therby making it near impossible to sustain
> combustion.
> 
> The demonstration showed the dropping of lighted matches into various
> fuel tanks partially filled (their most dangerous condition I believe)
> with petrol with no explosion or fire. Of course if the tank was
> ruptured the leaking fuel would sustain a fire but not result in an
> explosion.
> 
> I would have thought this would have been perfect for aircraft use as
> it can apparently be cut and stacked to fit almost any shape of fuel
> tank.

Couple of reasons money and money.

Consider that it costs several cents per flight mile per pound to
operate an airplane.  Adding several hundred pounds of aluminium
(remember that these are big tanks) will cost X dollars per flight
over the life of the aircraft, times the number of aircraft in
service.  (Let's also consider the costs involved with the
installation of the material.  If I have an airplane getting worked on
it's not makeing money, in addition to the actual costs to install the
stuff.)

Now consider how much it has cost because of the type of accidents
which this product would prevent.  I suspect that it would not be
many.  Most incidents involve massive damage to the wings, resulting
in complete rupture of the fuel cells and the resultant loss of all
integrety.  Unless you treat the fuel to reduce its flash point,
you're going to have a fire.

Fuel cell integrety systems are designed to prevent explosion within
the cell from shrapnel (gun fire, missiles, hot debre on a race
course) and relatively small breechs in the fuel cell itegrety.

Tenerrif (spelling) - two 747's collide on the ground.  Massive
damage.  No help there.  Continental DC-10 in LA - went off the runway
and sheared the wing off.  Massive damage.  Only two fatalities (they
opend their own exit door and jumped into the fire.)  Souix City?
Nope, ground loop big time. There go the wings again.

Whether we are comfortable or not with the fact, each of us has a
dollar value assigned to our skin when we sit in an airplane seat.
And it is a deliberate balancing act between making aircraft so safe
that they can't fly, and so poorly designed and maintained that no one
will use them.

A better solution was attempted seveal years ago to increase the
surface tension of jet fuel.  This would make it 'glob' rather then
'mist' during an accident.  Problem was that the additive was
relatively expensive, and it took special fuel 'preprocessors' to make
the fuel usable by the engines.  A demonstration was conducted on a
Boeing 720 (?), with the aircraft being flown (remotely of course :)
into a landing area which contained 'wing rippers.'  The pilot lost it
at the last moment, and the aircraft crashed into, rather then
through, the rippers.  The result was quite spactacular; and I'm sure
that you've seen the clip of a orange and white aircraft sliding into
what looks like telephone poles and exploding into a big fire ball.
This 15 seconds or so is very popular with the doom and gloom folks
who make the 'Why Airplanes Crash' type of documentaries.  NOTHING
would have helped the people in this type of accident; however the
test was considered a success in demonstrating that the fuel additive
was a failure.  Kind of convoluted logic, but it's official.

You might also investigate 'Cabin Misting.'  This is a scheme to mist
the cabin during emergencies to minimize the effects of cabin fires
and the resulting smoke and gases.  This IS a serious problem in that
many folks die as a result of fire and smoke following in an accident
that was otherwise survivable.  This system was pushed hard in Eurpoe,
and included a full scale test with real people (burning pans of jet
fuel inside a cabin yet!)  Reason you will not find it on any
airplanes?  Too expensive to carry the water around vs the cost to
compensate families of casualties following an accident.

Everthing we do has risks, rewards, and costs.  Failure to keep the
three in balance will result in a nonviable product (or service).

Just my opinions of course :)

Brian