chriscalandro Posted December 16, 2019 Report Share Posted December 16, 2019 One of the recurring themes with otherwise survivable crashes is the post crash fire. If there was a way to dump the fuel quickly I think it would increase the survival rate of accidents greatly? min the event of a forced off field landing does it not make sense to have some way of dumping the fuel? Not only would this reduce the fire danger it would also lighten the aircraft. why does such a thing not exist as a mod? Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted December 17, 2019 Report Share Posted December 17, 2019 Probably the possibility of failure (breaks away during turbulence for example) is the reason.I’ve wonder if bladders would provide better protection, but that would require extensive testing.Tom Quote Link to comment Share on other sites More sharing options...
EricJ Posted December 17, 2019 Report Share Posted December 17, 2019 46 minutes ago, ArtVandelay said: Probably the possibility of failure (breaks away during turbulence for example) is the reason. I’ve wonder if bladders would provide better protection, but that would require extensive testing. Tom It used to be that it was common in race cars/track cars to replace the stock fuel tank with a "fuel cell", which was usually a metal box with a bladder inside that was also filled with foam blocks. Usually the box was either put somewhere central was it was less susceptible to damage in a crash, or it had its own cage built around it (I had a car like that). The foam blocks stacked inside the cell around the central sump box, where the return lines fed and which typically had ball valves or flapper valves to retain fuel in the sump. The idea of the foam blocks is to slow down the rate that fuel escapes in a breach. It still comes out pretty fast, just not quite as fast as if the foam wasn't there. Without the foam blocks, which do reduce capacity a bit, they seem to breach just like anything else. Fuel cells seem to have fallen out of favor with many builders and now people just retain the stock fuel tank unless there's some compelling reason not to. There are some cool new fuel pickup technologies that reduce the need for in-tank baffling or foam, so stuff like that has reduced the need for custom solutions as well. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted December 17, 2019 Report Share Posted December 17, 2019 The bladders in these airplanes are extremely thick and durable, it’s like 3/16 thick rubber. I don’t know if there’s anyway to quantify that if you crash the airplane and the wings get disassembled. You may possibly see less spillage. I do not think it would be more Quote Link to comment Share on other sites More sharing options...
takair Posted December 17, 2019 Report Share Posted December 17, 2019 FAA is just mandating crash resistant fuel tanks for helicopters. The most basic part of this is the addition of a bladder, so it is a good indication that the FAA feels that bladders are beneficial. Obviously, the basic structure also comes into play as well as other parts. i think that large aircraft fuel dump systems are intended to get the aircraft closer to a reasonable landing weight and I don’t necessarily think it is directly aimed at reducing a fire in the event of a crash. Unfortunately, I’m not sure if a system in a GA airplane could work fast enough in the event of a typical low level event (takeoff or landing). Also, I would hate to be on the receiving end of the fuel. Quote Link to comment Share on other sites More sharing options...
chriscalandro Posted December 17, 2019 Author Report Share Posted December 17, 2019 I was reading something somewhere the other day that stated in the event of a power off emergency dumping the fuel is a priority if equipped. It depends on the scenario, but fuel evaporates pretty quickly. At a few thousand feet, if you had a hole the size of the drain, you could lose a tank of fuel quickly. if you’re headed for an unpopulated area, no problem, dump it as fast as you can. If you’re headed for a residential neighborhood, doesn’t it make more sense to dump a little fuel rain and have impact damage rather than impact damage AND a fireball? it seems like more often than not recently otherwise survivable impacts have ended with a fireball. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 18, 2019 Report Share Posted December 18, 2019 Interesting thought Chris... Its going to take a few tries to get a bunch of ideas fleshed out... 1) Emptying the tanks 2) Not emptying the tanks accidentally, warn the pilot when the tank is draining... 3) Robinson helicopters has gone through a lot of effort related to hardening their fuel tanks against really hard landings... 4) put a valve that can be actuated from the cockpit.... 5) System has to work without spraying fuel all over the plane.... 6) If I can only empty one tank....empty the right side where the door is... I’m going out that way if able... 7) If a tree is in your future... take the tree on the pilot’s side... again allowing exit out the copilot side... 8) We have a nice centralized internal location to drain fuel... the fuel strainer valve... 9) the fuel strainer valve would need to be optimized for the purpose... as is, it isn’t very fast, and it doesn’t stay open while draining only one tank at a time... 10) some other structural additions can put another layer between the tanks and the cockpit... and the fuel lines haven’t been considered in decades... In many of the accidents we see..... No fire... often means the plane ran out of fuel before landing... no hot surfaces, not excess fuel... There are a few threads around here on this subject. There is a video of a light airplane crash where the wing opens and the fuel sprays out... posted around here somewhere...no flames erupted in that video...(?) Tearing a wing open is going to be hard to defend against... but banging a wing around on hard ground shouldn’t turn into a conflagration every time.... take the ball and run with it... Add some ideas, no matter how goofy they may sound... Think twice before saying it can’t be done... reword it a bit to say what needs to be overcome is.... PP thoughts only, not a design engineer... Also consider getting the airbag seat belts... it helps to be conscious when getting out of the airplane... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted December 18, 2019 Report Share Posted December 18, 2019 They need to make the bladders with Kevlar fibers, give it puncture resistance and greater strength.Tom Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted December 18, 2019 Report Share Posted December 18, 2019 On 12/16/2019 at 2:48 PM, chriscalandro said: One of the recurring themes with otherwise survivable crashes is the post crash fire. If there was a way to dump the fuel quickly I think it would increase the survival rate of accidents greatly? min the event of a forced off field landing does it not make sense to have some way of dumping the fuel? Not only would this reduce the fire danger it would also lighten the aircraft. why does such a thing not exist as a mod? I suspect the accident data doesn't support it. one of the more common causes of crashes overall is fuel exhaustion for starters. And the most common phases of flight to see crashes and fatal crashes are landings and takeoffs respectively, so they're not exactly times you'd be planning on dumping fuel... 1 Quote Link to comment Share on other sites More sharing options...
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