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Date: Mon, 03 Jan 2011 08:35:34 -0500
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Subject: Fuel Dumping
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The only reason I'm aware of why designers include a fuel dump capability=
 is when they design a landing gear system which cannot handle the maxmum=
 takeoff gross weight.  This is often the cse on large jets -- think of an=
 airliner which may have a gross weight double that of its typical landing=
 weight.  In this case, a landing required immediately after takeoff would=
 require a fuel dump, which could easily be a 15 minute process.

I know of no cases where designers include a fuel dump provision to reduce=
 post crash fires.  That's not to say the idea is without merit, but I wou=
ld not bother with it.  Instead, I would take measures to prevent inadvert=
ent fuel release after a survivable crash.  I'm not sure how to do that --=
 would a flexible fuel line (say, steel braided) be less likely to tear th=
an a hard aluminum line?  Would a silicone fireproofed fuel line be less=
 likely to rupture (those puppies look pretty indestructible)?  What about=
 a header tank -- I imagine that five gallons of fuel just above your knee=
s is not a good place for a fuel leak (and yes, my airplane has the header=
 tank).

But dumping the fuel before an off-airport landing?  I don't think I would=
 do that, but that's just me.

- Rob Wolf

p.s. the NASA test in the early 1980's involved a remotely-piloted Convair=
 720 with an anti-misting additive in the fuel.  As I recall, the remotely=
 piloted airplane did not hit the intended point on laning and thus the ob=
jects intended to puncture the tanks, well, ithey pretty much ripped the=
 wings apart, releasing the fuel all at once.  This was a test failure and=
 the explosion-inhibiting anti-mist additive was not adequately tested. =
 Needless to say, they did not repeat the test.

http://en.wikipedia.org/wiki/Controlled_Impact_Demonstration

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<font color=3D'black' size=3D'2' face=3D'arial'>
<div>The only reason I'm aware of why designers include a fuel dump capabi=
lity is when they design a landing gear system which cannot handle the max=
mum takeoff gross weight.&nbsp; This is often the cse on large jets -- thi=
nk of an airliner which may have a gross weight double that of&nbsp;its ty=
pical landing weight.&nbsp; In this case, a landing required immediately=
 after takeoff would require a fuel dump, which could easily be a 15 minut=
e process.</div>


<div>&nbsp;</div>


<div>I know of no cases where designers include a fuel dump provision to=
 reduce post crash fires.&nbsp; That's not to say the idea is without meri=
t, but I would not bother with it.&nbsp; Instead, I would take measures to=
 prevent inadvertent fuel release after a survivable crash.&nbsp; I'm not=
 sure how to do that -- would a flexible fuel&nbsp;line (say, steel braide=
d) be less likely to tear than a hard aluminum line?&nbsp; Would a silicon=
e fireproofed fuel line be less likely to rupture (those puppies look pret=
ty indestructible)?&nbsp; What about a header tank -- I imagine that five=
 gallons of fuel just above your knees is not a good place for a fuel leak=
 (and yes, my airplane has the header tank).</div>


<div>&nbsp;</div>


<div>But dumping the fuel before an off-airport landing?&nbsp; I don't thi=
nk I would do that, but that's just me.</div>


<div>&nbsp;</div>


<div>- Rob Wolf</div>


<div>&nbsp;</div>


<div>p.s. the NASA test in the early 1980's involved a remotely-piloted Co=
nvair 720 with an anti-misting additive in the fuel.&nbsp; As I recall, th=
e remotely piloted airplane did not hit the intended point on laning and=
 thus the objects intended to puncture the tanks, well, ithey pretty much=
 ripped the wings apart, releasing the fuel all at once.&nbsp; This was a=
 test failure and the explosion-inhibiting anti-mist additive was not adeq=
uately tested.&nbsp; Needless to say, they did not repeat the test.</div>


<div>&nbsp;</div>


<div><A href=3D"http://en.wikipedia.org/wiki/Controlled_Impact_Demonstrati=
on">http://en.wikipedia.org/wiki/Controlled_Impact_Demonstration</A></div>
</font>

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