I don't think that opening up a discussion of the chemistry of pyrolosis has any benefit in a general aviation thread titled "parachutes".
I didn't open up the discussion to that topic, you did. When you said "
In perfect theory, fire requires three things in adequate proportion: Fuel, heat, and oxygen," in "perfect theory" you were wrong. You were also wrong to state "
Aside from the gasoline, which you have now turned off, there's not supposed to ba any other exposed fuel up there. Master off, the heat is no longer supplied to an electrical fire."
Clearly you've never had such a fire. I have. I didn't just do a "
firefighter refresher this month" either, but I do have nearly 20 years of professional firefighting experience, and have dealt with such fires in flight (as an aerial firefighter) and on the ground.
Master off means switch off in the cockpit. Think about which side of the firewall the battery master relay is located; the switch only controls the battery master relay, and if that's bridged, then you still have electrical power available. Further, while many light airplanes use lead acid batteries, (their own hazard, if you've ever seen one explode;
I have), many airplanes also use NiCad batteries, which can create self-sustaining thermal runaways.
As for oil not becoming combustible, oil burns very well, and oil in contact with hot exhaust and forced ventilation can easily translate into a fire. Oil can come from a failed cylinder, a cracked case, a broken pushrod tube, a failed crankshaft seal, a failed turbo bearing seal, a failed turbo supply line, and other such sources.
I don't think that opening up a discussion of the chemistry of pyrolosis has any benefit in a general aviation thread titled "parachutes".
I didn't open it up. I didn't open up a discussion about shooting one's self to avoid flames, either, but they were put on the table. The hollywood suicide garbage has been gently put to bed, I think but it's you that's perpetuated the discussion on fire and airplanes, so by all means, let's discuss. Burying your head in the sand with comments like "
have no fear" is little more than saying "
it's alright, kids, it can't happen to you." Yes, it can.
If a fire has occurred forward of the firewall, the ignition source is not necessarily removed from the fire by turning off the master. The ignition source may not be electrical, but if it is, shorts due to the fire may have removed this option from you; you're moving a switch in the cockpit, not actually moving the battery master relay; lose the ability to have that control from the cockpit by one or both wires from the battery master switch, and you've lost control of the battery master relay, and of the electrical system. This can happen as the result of a short. I've experienced it.
The mag can certainly continue to present as an ignition source, which is part of the reason that the mags are turned off as part of the engine shutdown procedure.
Oil can certainly be present in the nacelle or cowl area. Ever had a lifted jug that separates the pushrod tubes and allows oil to pump out? Ever had a cracked case, or failed cylinder? I certainly have. Ever had an oil fire? I certainly have. If you haven't experienced these things, you shouldn't assume they don't happen, aren't possible, or shouldn't be considered. These events are real, they do happen, and if they're outside the realm of your experience, you do no one a favor by dismissing them.
Engine oil vapours are rarely exposed to heat and oxygen in concentrations which support fire.
Rarely, like leaving an oil cap off on one's Cessna turbo 210? I saw that two years ago. In fact, I've seen quite a few folks take oil baths after leaving the filler cap off. You don't think a hot turbo can transform that into a fire? Ever seen just how hot a turbocharger gets? Ever fly a Navajo at night?
Rarely, like seeing all the oil pumped out of the engine onto the exhaust in a Cessna 337? I saw that a couple of years ago, too. Rarely, like a cylinder lifting, or a failed jug, or a jug that leaves the airplane; I've seen that many times over the course of my career. I've had it happen, I've repaired such failures, and I've seen the damage. In many cases an oil fire doesn't occur; I think it's safe to say that the majority of the cases don't see an oil fire. Every single one of them has the distinct potential, however, and that potential is what we consider.
We're unlikely to see a need to shoot ourselves in the cockpit. That's not realistic. The potential for an engine failure, electrical failure, hydraulic failure, cockpit fire, cabin fire, or engine fire is realistic, however, and it's for this reason that we have such procedures in aircraft flight manuals.
Though a pilot is required to have a fire extinguisher in the cockpit, and that it's presupposed that pilot will use it there, if the circumstances dictate, in this forum, it is unlikely that pilots have extinguishing systems in the engine compartments.
You've never had to discharge an extinguisher on the ground for an engine fire? Really?
A member of this forum recently purchased a Twin Commander. His particular model probably doesn't include the fire suppression system, but some do. One I flew last year did. I've seen them installed in other general aviation airplanes, too, as I'm sure you have. People frequent this forum who use all manner of light airplanes; not everyone flies a Cessna 172, so yes, it's entirely possible that a private pilot posting here may use or may purchase an airplane with a fire suppression system installed for the engines and/or engine accessory system. A Cessna 421 that I flew a couple of years ago had one in it, for example.
Additionally, the Twin Commander has fire procedures that go beyond mixture, mags, and fuel. The Twin Commander has hydraulic to consider. Anyone here who flies a Cessna 172RG, 177 RG, 182RG, or 210 should consider the potential for a fire in an electrohydralic pack. I had one several years ago. It continued burning until I got on the ground and put it out with a fire extinguisher. The electrical couldn't be terminated in that case, incidentally, because due to a fire, the master relay had welded itself closed, providing continuous power that I couldn't interrupt. Go figure. (I suspect you're thinking "circuit breaker" presently, but circuit breakers don't always work (had one burn up in a lear several years ago, requiring a return to the airport with smoke in the cockpit), and circuit breakers don't protect components; they're installed to protect wiring.
In a nutshell, despite your attempt to dismiss, these are realities and burying one's head in the sand does no one any good.
Will most posters here ever see these things? Likely not. That is irrelevant.
Most posters here will not see many of the things that happen or can happen in airplanes. Knowing that they can and do happen, knowing that procedures are laid out for them, and knowing those procedures and the systems and what must be done, is critical regardless of whether these things occur. The mere fact that they can occur is enough.
For the engine types prominate in this forum, I would suggest that engine oil fires are very rare, and as there is very little the pilot could do if there were such a fire.
I'm a mechanic and inspector. I disagree.
If one is flying an aircraft which meets the design requirements, the pilot has control of the alternator/generator field, so have no fear pilots, you'll be able to turn off the master, and remove that ignition source if you need to.
Not in a fire. When all is functioning well and properly, you have control. Not necessarily in a fire. When insulation is burned, components melt, shorts occur, you have no idea what you have control over. Not in a fire.
Further, a generator bearing failure, or fire near a generator can quickly become a class D magnesium fire, and that won't be put out. Whether the electrical power is removed by opening the battery master relay, whether the generator field is cut, the generator always produces , and the appliance itself is also an ignition source that can spark in operation. So long as the engine is turning, the generator is also turning, and therein lies another potential source of ignition, and fire.
Getting pilots here worried about engine oil fires and uncontrolled electrical sources foward of the firewall really has little value in pilot mentoring in my opinion.
Burying one's head in the sand has very little value in my opinion. Neither of our opinions are of any consequence here, however. These things can and do happen, and it's for that reason that manufacturers include procedures for them. Manufacturers don't include procedures for shooting one's self in the head; that's fanciful. Having an engine fire or other inflight emergency is not fanciful; it does happen, it is a reality,and one should be prepared for it, know the specific actions necessary for the make, model, and serial number of airplane that one is flying, and be prepared to execute the memory items from that procedure without hesitation.
Again, I didn't introduce this topic. I did address it. Then again, I don't see much discussion on parachutes being tossed around any more, so here we are.
The notion of thread drift as a fault is idiotic. I don't recall ever having been in a conversation with anyone when someone actually piped up and said "I'm sorry, but that wasn't part of the original sentence spoken by the first person to open their mouth in this conversation, and therefore we can't talk about it." That would be stupid. Likewise, all conversations drift somewhat, and as fire was introduced in this thread, it's continued along that vein quite naturally. Nothing wrong with that at all. The only time it is a problem occurs when someone can't contribute to the thread (doubtless the forums most prolific poster will be along shortly to rectify that).
It would be unfair of me to suggest that aircraft fires do not occasionally occur, and that a few of those are not serious.
Yes, it would.
My inclination would be the reverse as fuel selector off halts the supply of fuel. Mags left on should get rid of the fuel in front of the firewall in the most acceptable manner.
Throttle to idle and mixture off before fuel selector off would trap the fuel in the firewall forward fuel system where there is most likely a leak
Discuss.
Don't get too rambunctious guessing about the procedure you *think* would work, vs. what the manufacturer provides. Know your systems, certainly, and remember that not all situations can be accounted for in canned procedures, but don't discount the basic procedures set out, either.
Pilots have been seriously injured in the past when they took off with a fuel selector off or switched the selector just prior to takeoff to a tank with water or bad fuel. The engine can continue to run just long enough, even at takeoff fuel flow settings, to get you into the air and in the worst possible position.
On the ground, shutting off the fuel selector may do little more than give you a long wait while the fire burns. Shutting off the engine may be important for several reasons, and the fire source may not be what you think.
A failed induction tube or induction section isn't uncommon. I've seen quite a few airplanes over the years that had damaged or burned flexible couplings in the induction (many light airplanes use them); these leak, or come off, or get blown off during a backfire, and clamps loosen or fail. Some engines with tightly packed exhaust and induction use heat shields to protect these couplings, but they fail, and they fail often near the exhaust outlet from the cylinder head, or near the cylinder head. These can pump out the perfect fuel air mixture.
The diaphram in the fuel flow divider can fail, pumping fuel overboard, often directly on top of the engine. Fuel lines can fail, injector lines can rupture, as can primer lines. Carburetor floats stick or sink. I've seen some very large fuel leaks occur over the years.
If you truly understand your system and know the immediate problem and can work through it given unique circumstances, then you may require unusual steps to tackle the problem. Generally, however, making up your own procedures isn't a wise idea.