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One more opinion,
If you look at most of the crashes, that occur there is little time to worry about how much fuel is in the tanks. I believe ones attention is best spent getting the airplane down and managing the situation especially when flying a slippery high performance airplane. We already have too many distractions..
I hate the thought of landing with lots of fuel, but the prospects for getting it out of the airplane are impractical..
Randy Snarr
N694RS
"Flight by machines heavier than air is unpractical and insignificant, if not utterly impossible"
-Simon Newcomb, 1902
--- On Mon, 1/10/11, rehbinc@aol.com <rehbinc@aol.com> wrote:
From:
rehbinc@aol.com <rehbinc@aol.com>
Subject: [LML] Re: post crash fire control
To: lml@lancaironline.net
Date: Monday, January 10, 2011, 12:10 PM
Kevin,
While I know that some (many?) commercial aircraft have dump capabillity, I don't know just how they go about it.
I don't have any experience with the valve you reference. From the picture, it doesn't look inherently leak tight but maybe it is. It also isn't clear how you would install it, especially in series for redundancy.
If you want to add such a capabillity to your aircraft, you need to carefully consider the added failure modes the modification brings. Just remember that adding another engine statistically makes you less safe. If I were going to do this, I would have double valves at each drain with a way to test both leak tightness and valve operation independently at regular intervals. Obviosly, you also want a pretty fail safe way to ensure that you don't accidently dump the fuel, either in the air or on the ground. Consider what happens if only one wings emties when you pull the actuating lever.
I'm not saying this is a bad idea, just that you want to think it out thouroughly before implimenting it. As I said earlier, if I was in a situation where the tank was likely to be ruptured, I would prefer to have as little fuel as possible in the tanks as possible.
Rob
Rob
-----Original Message-----
From: Kevin Stallard <Kevin@arilabs.net>
To: lml@lancaironline.net
Sent: Mon, Jan 3, 2011 8:35 am
Subject: [LML] Re: post crash fire control
Are you putting in a lavatory in your Legacy?
I have been thinking about this for some time and am glad the occasion has come up to discuss it.
I am building a Legacy and was trying to figure out how to incorporate a dump valve into each wing to dump the fuel for certain cases of emergency landings or imminent crash.
So far I came up with this valve:
they offer it with a stainless steel paddle in 2" & 3", one could be mounted at the bottom of each wing at the lowest spot to dump the fuel.
I haven't really done much research into wether or not the aviation industry offers such a valve, or the compatibility of the materials with the fuel or the reliability or temperature and pressure limits, or how air will get into the tank to replace the fuel, but it seams like the logical general direction?
Of course, one fear would be inadvertent dumping of the fuel or leaks.
On Dec 31, 2010, at 1:10 AM, REHBINC wrote:
I am a forensic engineer and work quite a bit with fire and explosion as well as mechanical/structural failure.
If I had a way to drain the fuel before crashing, I would get the tanks as dry as possible. A couple ounces of gasoline trapped somewhere in the tank would be plenty to make the space fuel rich. It isn't realistic to expect the entire tank to be fuel rich before impact, but a portion of it certainly will be. It is all a matter of time and temperature. In tank ships, you need around 2 gallons or so to make the space fuel rich. Frequently there is more than this trapped behind the tank scale.
For the reasons stated earlier, I wouldn't be too concerned about an explosion risk of the wing tanks (At least as long as I wasn't standing on it at the time!). My biggest concern would be the size of the fuel puddle the plane came to rest in. A hundred gallons spread out on the runway could make a real big fire real fast and would be difficult to survive if you were caught in the middle. Two cups of gas in the same scenario would be a much more survivable situation.
Another benefit of draining the tanks before impact is the reduction in gross weight and therefore stall/impact speed.
Rob, interesting info.
So sounds like if you do have a quick drain, you don't want to completely empty it.
I have no idea how to build a quick drain that would not create some leakage risk.
sounds like you are in this business?
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