So after watching all those Mayday/Aviation Disaster shows…I wonder, can’t some kind of fuel suppression system be installed? Not a fuel dump, but some device that would introduce chemicals into the fuel to render it to be no longer flammable.
This would be used on takeoff disasters when there’s no time dump the fuel, but it’s clear the plane is going to crash (too heavy, shifting weight…etc…)
On some aircraft there are systems that put nitrogen in the fuel tanks as the fuel level decreases. This is more to stop a fire from happening from static electricity or a wiring problem. It certainly wouldn’t help once a fuel tank broke open.
My first thought is if there is even such a chemical.
Next is that even a small airliner could have 5,000 gallons of fuel on board in 2 or more tanks. How could you mix such an unknown chemical into that much, or more, fuel quickly enough. You would have to do it in a couple of seconds.
Next even if such a thing were possible, it certainly would be bad if such a chemical accidentally got mixed into the fuel as it would shut down the engines.
There was some work on this in the late 90s.
There is a proceedings (abridged) avaialble on google books : Aviation Fuels with Improved Fire Safety
You can buy the proceedings from Amazon too. There are quite a few ideas discussed here - you can find the book in your library too.
Jet-A (commercial avegas) is already about as nonvolatile as a petrochemical can be and still be a useful fuel. There is no way to spontaneously change the chemical formulation to something that won’t burn. You can, of course, add fire suppressants which essentially starve the fuel by displacing oxygen (CO[sub]2[/sub] or Inergen), bind with the free hydrogen ends to prevent oxidation (halomethanes), or just absorb energy to reduce the reaction below a sustainable threshold (pentafluoroethane). However, this requires about as much suppressant as it does available fuel and oxidizer, which would obviously be impractical to carry on an airplane.
Realistically, modern commercial aircraft are about as safe as materials, controls, and avionics technology are able to make them at the current state of the art. Despite the fact that an aircraft performs an essentially impossible function–keeping tons of loosely aggregated material suspended in mid-air for hours at a time–the rate of actual failures is so low that even if you travelled by aircraft on a daily basis you are more likely to suffer a serious injury at home or driving to work. To the untrained eye, it may seem that this is because building, flying, and maintaining aircraft is a simple and routine task, but a more-than-cursory look at the entire chain of design, testing, training, inspection, maintenance, and regulatory control shows that this record of safety comes not from the innate lack of hazard but an unreasonably complex and highly engineered overarching system. The general public gets upset when a plane crash occurs because pilots weren’t trained for certain hazard conditions or an incipient failure in an elevator control actuator wasn’t discovered, but really, given the complexity of a single aircraft, much less the systems that let dozens of them land and take off at an airport in the span of an hour, it is phenomenal that they aren’t falling out of the sky every day.
Stranger
Agreed - Jet-A has a high flash point and a low flame speed.
IMHO, True and misleading and maybe out of context. OP asked about suppressing flames from a collision. In fact there are a few fire resistant formulation of fuels being researched / demonstrated / patented. Here is Self-Extinguishing Fuel Chemistry and here are picturesof a test comparing JP-8 (Military version of Jet-A) versus Diesel FRF (See page 6 of 14)
Fire resistant fuels are also being test for combat vehicles.
Again, IMHO misleading. Maybe true for commercial aircraft but the military aircrafts used such agents primarily to protect the ullage. (F-16s used halon). Here is a more detailed paper.
This whole paragraph reminded me of Douglas Adam … they still think digital watches are a pretty neat idea…
In my opinion airplanes are as safe as people are willing to accept. There’s still room to improve. As to complexity, they are not overly complex from a systems point of view. There are more complex systems : for example an oil refinery will have I/Os which are an order of magnitude higher than an airplane. The layers of safety and redundancy in many chemical plants will make an airplane look like a toy.
In the early 1980’s attempts were made to develop a fuel additive that would reduce the fuel’s tendency to atomize. Finely atomized fuel - whether solid or liquid, volatile or not - supports combustion very well. In the end, they came up with AMK - Anti-Misting Kerosene. In 1984 NASA did a full-scale test, deliberately crashing a 707 loaded with AMK in an attempt to see whether it would in fact burn in a real crash.
The test did not go well.
Smoother footage of the actual crash at this link.
Admittedly, they had created a worst-case test scenario. The runway threshold had been fitted with an impact barrier and stanchions designed to deliberately rip the wings open and spill the fuel. As luck would have it, one of the stanchions ripped directly into an engine, providing a reliable ignition source for the cloud of semi-atomized fuel. In the end they learned a lot from the test, but one of the things they learned was that the increase in post-crash fire resistance of AMK was not enough to justify the expense.
I suppose an “eject the warp core” system ultimately has too many cons: Accidental loss, pilots panicking and dropping a bomb over a city.
on a slightly related note…I wonder if getting caught with a parachute in your carry-on gets you an automatic two-hour interrogation.
Here’s a more practical question: Why don’t passenger planes carry drag parachutes for a too fast landing? Yes, you would almost certainly never have to use one…but it seems easy enough to install.
You beat me to it.
Thanks for mentioning that. Many people think jet fuel must be Super Gas because… well, it’s used in jets! In fact, the 87 octane you put in your car is much more volatile and explosive.
But an oil refinary can make space and accomodate the mass of a large fire suppression system. An aircraft would have to carry suppressants and the deployment system on board. It would be impractical from a carried weight standpoint for an aircraft to carry enough suppressant to extinguish any possible fire from mass fuel release that would occur in the case of a catastrophic structural faillure of the tankage. As a practical matter, commercial aircraft are essentially designed to be as safe and fault-tolerant as they can be made with the state of the art, save for manufacturing defects and inherent risks with energetic systems such as batteries and fuel, and the systems that support them (air traffic control, ground fire safety, automated radar track, landing and approach systems) are highly complex systems that have evolved through many millions of person-years of effort and experience.
The additives for this are a class of substances called surficants, and are designed to reduce the voliatility of the fuel. Unfortunately, by the same token they make the fuel more difficult to ignite the fuel in the engines and often cause problems with contaminating and clogging vales, lines, and filters.
Stranger
Any time you think of a safety measure that might save lives, and you notice it hasn’t been implemented in commercial aviation, there’s a good chance it’s because it wouldn’t save enough lives to justify the cost.
Think of how often you hear of a plane overshooting the end of the runway. Once every couple of years? It happens, sure, but it’s awfully rare; Wikipedia lists just 30 incidents.
Now think of how many people die each time this happens. Not many.
Now imagine the cost to develop, test, certify, install, inspect, and maintain drag parachutes on 20,000 commerical aircraft.
The price tag would be in the many billions of dollars.
To save maybe a couple of lives per year.
BTW: Even that low incidence rate of runway overshoots is being addressed at many major airports by installing EMAS - crushable concrete foam blocks that quickly stop airplanes by letting the landing gear sink in.
The oil refinery reference was in reference to complexity of control and number of variables that can go wrong. I agree with impracticality of carrying massive flame suppressant. However there are other methods of flame suppression as I have pointed out in the references. Moreover, if the Natural gas boom continues and airplanes shift to LNG (Liquified Natural Gas) (see press release by Boeing ), the OP’s problem may resolve itself.
There already areLNG powered transport airplanes.
I am an engineer by training and have myself used the above “state of the art” argument and know it is never really true. For example in the Aircraft context, the NOX emissions from a airplane engine is not state of the art. In fact when many of the aeroderivative engines are modified for power production, steam or water injected NOX suppression methods are added.
Also for example when it comes to noise and noise suppression at airports, airplanes can hardly claim that they have “State of the art”.
It all boil downs to what the public is willing to live with ultimately.
When I was an active skydiver I carried my gear on the plane many times with zero problems. There’s nothing dangerous in there and it’s not like somebody can pop the emergency exit door open at cruising speed/altitude to go for a jump.
Of course…I just figured someone may think, “What do you know that we don’t?”
I Googled “avegas”, but failed to find any relevant hits.
“Avgas” produces lots of links - but it has little to do with Jet-A. It stands for “aviation gasoline” and is the fuel used in most aircraft spark-ignition piston engines.