inflight fire
 

Reposting an older article that is still timely.

Good article, and it doesn't matter that it wasn't written yesterday.

My usual response to talks about onboard fires is that there's nothing better than the smell of smoke in the cockpit, but that has to be qualified by noting that I've spent a good deal of my career fighting fires from the air, so smoke in the cockpit is also the smell of money.

I've had several on board fires over the years; Janitrol heaters twice, a burning hydraulic pump once, and engine oil from a failed engine component on a large radial. The heaters were put out manually, using a nomex jacket to smother the fire as well as stopping the fuel. The oil went out as the supply stopped with shutdown. The hydraulic pump, however, did not.

In the case of the hydraulic pump, it was a single engine turbine aircraft, and in the time it took to make an overhead at the runway, over the numbers, until touchdown, the cockpit went from a trace scent of burning insulation to a cockpit full of smoke. On the rollout, by midfield I couldn't read the instruments. Point is, it went fast, as fires do. The rule of thumb is that a fire doubles in size every 60 seconds, though the acceleration isn't linear. There are no guarantees that adequate time exists, and there's a good chance that it's not long. Getting to the ground and getting out is critical.

Just as the article notes that descent increases fire behavior, once on the ground venting the aircraft does, too. Every door that's opened will increase fire behavior, and also change the direction that the fire moves. Anyone that's ever blown on a campfire understands why.

I've been doing fire in one capacity or another much of my adult life and the one solitary piece of advice I can give, when it comes to fire, is that there is no such thing as a false alarm. Every firearm is loaded, and every fire alert should be taken seriously. Very, very seriously.

Great response, fully agree, thank you!

Are you the author of that article, by chance?

It's well written, and takes a different tack than most commentary about inflight fires. I thought it was well placed and very well presented.

Yes. Thank you!

That was fantastic, and terrifying. I long ago read an article about a ‘17 minute’ rule - 17 minutes being a golden number between first indication and losing the aircraft. I thought I had downloaded it but can’t find it.

About 10 years ago when working for a long haul VIP charter, we had the opportunity to train with the flight attendants on a simulated in flight fire over the water (it was a one jet, small company). Could we find all the emergency equipment, could we coordinate, etc. I think it’s safe to say we were all deeply humbled and unimpressed with our knowledge and perceptions on just how ‘good’ we were.

Thanks for sharing!!!


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Ptarmigan;

Thanks for posting an interesting article, it's a topic I think about on every ocean crossing (777 cargo). I think there is some disconnect on the history of inflight fires and the current procedures to cope with them. I'll try and be brief, await others thoughts, and hopefully have a decent discussion on the topic.

The history I refer to is the "20 minutes", an amount of time commonly agreed upon as the flight time remaining with an onboard fire.

The current procedures (cargo) I refer to are a descent to FL250, depressurizing, and cruising until 60 miles from landing (this could be over an hour).

Here is my take on the disconnect. If I get a main cargo deck fire warning (and I have to assume it's real) I start a mental (if not physical) 20 minute timer. Where do I want to be when that time runs out? At FL250, 45 mins from land? Hoping the engineers are right about starving the fire? Is it a lithium battery fire (10,000lbs on my last crossing) and it will never starve?

Would it not be a better use of time (the rest of your life) to descend immediately to a safe ditching altitude (say 1000'agl) and analyze the situation? From FL 330 it would take 20 minutes to get down and prepare to ditch on a good day, any delay with investigation and fire checklists at altitude will take you out of your 20 minute survivability window.

At 1000'agl, assess the situation. Is it a real fire? If so, you are ready to ditch. If not, you have the fuel to climb back up and divert (which you were going to do anyways).

I'm not an expert on this topic and am open to hearing others thoughts......

Tradeoffs. The fire will burn much better at 1000' than at FL250.

But like you say, if it's a big load of Li, then the O2 partial pressure isn't going to matter much either way. If it were me, and there was no Li onboard, I'd stay at 250... you can breath with the mask but a normal fire really can't.

True, the fire will probably will burn better at 1000agl, but I believe its going to burn regardless. If there are findings out there that cargo fires extinguished on their own by oxygen starvation, I'd feel a bit better, I just haven't heard of this happening.

With no Li onboard, wouldn't you be better staying at cruise altitude (FL330?), or climbing as high as possible, to starve the fire? If FL250 is good, then FL370 is great. Obviously we are talking no pax here, and you are going to have to see a doc for the physiological impact, but if you are putting ALL your faith in oxygen-starving a fire, you might as well go all in and climb.

As an aside, how do you know you don't have any Li onboard? Crew bus driver says there's a lot of "undeclared" DG.

FL250 is about the highest cabin pressure where you can stay fully functional using a standard O2 mask. Much higher and you might get bent and would have too low of a partial pressure to not be impaired.

Any normal fire is probably going to go out at that altitude. Only something with its own oxidizer, or that burns hot enough to oxidizer other materials, will keep going.

From a chemistry perspective, 250 should do the trick.