Wispy smoke begins streaming around the cowling and quickly thickens. Fire! I’m alone in our Cessna 180. My adrenaline flow redlines. After a few seconds considering my options, I turn the master off, grab a piece of equipment, push the left door open, and jump. No parachute.
No parachute? Didn’t need one. The 180 was sitting in front of our hangar on the South Line at Cincinnati Lunken. It was a crystal clear, frigid, don’t-lick-any-metal- flagpoles Saturday morning. I had intended to warm up the engine while waiting for my partner to return after he drove off to retrieve something from another hangar. Our mission of the day: Find the $100 hamburger. This was way before Sporty’s free Saturday hot dogs.
In a heartbeat, my good intentions had produced the most dreaded word in aviation: Fire! My mind went into that hyper-speed thing where time is measured in nanoseconds. Probably a stack fire, I say to myself. Crank the engine to suck up the flames.
But another voice in my head cried, What if it’s something else. Something that could be worsened by cranking the engine. But what? Electrical?
Question: When was the last time you practiced recognizing and extinguishing stack fires? How many of you have ever gone to the airport saying, “Today I’m gonna start a stack fire and practice putting it out?”
We practice engine failures ‘til we’re blue (or green) in the face, but I don’t know anyone who practices stack fires. We’re instructed as to the likely cause of stack fires and what to do if we have one. But we don’t practice them.
On that icy blue morning, I had pushed the primer a couple of times and cranked the starter. No start. Well, maybe a little more prime will do it, I erroneously thought. Still no joy on the second try. But then the smoke starting curling up around the cowling.
We all know the drill for a stack fire. Seems pretty simple when you’re sitting at home in your comfy chair reading about it or when your instructor holds forth in the FBO office. “Just keep cranking the starter. It’ll suck the flames back into the engine.”
Simple… IF it is a stack fire. But was my fire a stack fire? Lots of combustible things under that cowl. Could engaging the starter make it worse? Perhaps irretrievably so?
“Hey, dummy,” you say. “It’s a cold morning. You over-primed the engine. You have a stack fire. What else could it be? Crank.”
Odds are you’re right. But I didn’t feel like playing the odds that morning when losing the bet could possibly destroy the airplane.
The nanoseconds were ticking and the smoke was thickening. I knew what to do IF it was a stack fire. But I didn’t know how to positively recognize it as a stack fire versus a fire of another origin. Is it like watching the Vatican chimney? The color of the smoke? It was a classic set-up for a stack fire, but I’d never seen stack fire. Could cranking make things worse?
My gut tightens, and I say to myself, “Probably a stack fire. I should crank. The fingers of my left hand press against the starter switch key with almost, but not quite enough, pressure to engage the starter as I debate with myself. I glance at the Ammeter. Nothing abnormal. And no circuit breakers popped.
A lifetime of five seconds or so had passed since the smoke first appeared. Decision time!
“Crank”, you are screaming. “It’s a stack fire.” Easy to say if your chair doesn’t have a nose emitting smoke.
The nanosecond clock ticked on as the smoke billowed. Crank – and take what was a small risk that doing so would make matters worse, or grab the fire extinguisher and exit the airplane? I took the one-plan-fits-all approach and unstrapped the extinguisher from the floor between the front seats before exiting the aircraft.
I liberally applied the foamy white fire suppressant material to the stacks and engine compartment. I was not careful where the stuff went. I had only one thought: PUT OUT THE FIRE! Deal with collateral damage later.
As it turned out, you were right. It was a stack fire. And fortunately the engine was not damaged by my inexperience with stack fires and fire extinguishers.
It’s stack-fire season. Picture yourself after a failed start attempt on a frosty morning. Smoke starts curling up around the cowl. To make matters worse, your family is in the airplane with you. You have only a few seconds before someone yells, “Fire!”, and general panic ensues.
Crank? Don’t crank?
Someone please tell me how to positively identify a stack fire. And someone please tell me whether cranking could ever make things worse if it’s not a stack fire. Your enlightenment would be most welcome if you care to comment.
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Frosty frigid morning? Probably just as cold in the hanger? If engine is preheated before starting, would that prevent a “stack fire” as well as prevent undo engine wear on such a cold start? First time I have heard of a “stack fire”. Low time private pilot (130 hrs) Interesting experience that’s for sure!
You didn’t mention it, but I presume you also shut off the fuel selector . . . . . ?
I play odds a lot, and I tend to think an induction or exhaust fire is probably far more likely to get out of hand than the melted insulation that may result from a wire with worn insulation or a smoked solenoid.
(On the ground)
Now if I was in the air – that’s a whole different ball game.
Oh, so anyway, I’d crank away
In 7000 hours I’ve had two fires, one was a stack from an overprimed Continental in a C150. Starting the engine did put it out quickly. The other was in the air in a Viking Lycoming 300, filling the cabin with smoke and with the gear suddenly falling into down position, responding to its excellent fail safe design. After declaring an emergency with ten miles to an airport, I landed in a crab, all systems off, while looking out the pilot window and rolled to a stop by the fire truck. Huge smoke but no flame. Bottom line was that the collar at the back of the exhaust manifold had come loose, allowing the hot exhaust to burn through the landing gear hydraulic pressure line. Hooked it up and continued gear down.
I did it one cold morning attempting to start a 172 without preheat. Lots of prime, then cranked….and cranked, no luck. I should have used the primer, but instead I pumped the throttle twice in hopes that the accelerator pump would spray additional fuel into the intake and let the engine start. When I cranked again, there was a muffled backfire, so I took my hand off of the key and watched. Sure enough, smoke! Without hesitation, I cranked for another minute, eyeing the extinguisher on the floor and figuring out how to get help if my portable extinguisher was not up to the task. The cranking worked, no fire, no need for the extinguisher. I pulled the air filter and sure enough, the induction air box was black and the paper air filter element was black on the back side.
On engines equipped with updraft carburetors, refrain from pumping the throttle, especially if you are not cranking. The accelerator pump sprays fuel into the throat of the carb, but since it is mounted to the bottom of the engine, the fuel will end up puddling in the airbox if there’s no air flow to suck the fuel up into the engine. Also, when cranking to suck up any suspected flames, turn off the fuel selector and pull the mixture.
An engine mounted preheater and a long extension cord forever cured my cold start problems after that experience.
Excellent info. Thanks.
Happened on a shirtsleeve day after flying to a nearby airport for lunch, after which the rented Cherokee 140 wouldn’t start. The battery was getting tired. Made the mistake of over priming, then pumping the throttle while cranking. Heard a muffled backfire. Waited for the battery to recover and tried cranking again. Saw a wisp of smoke come out the nose. Tried cranking, but no start. Got out and opened the pilot side cowl – flames flared up, reminded me of looking at a well developed cozy fire in a fireplace. Looked for a fire extinguisher, saw one on a nearby lightpole. By the time I got to the lightpole a pickup had pulled up with a fire extinguisher and put out the flames. Wasn’t sure of the damage so got a ride home from another restaurant customer.
One thing to definitely remember: Unless the bloody airplane is near a building, or a flammable liquid truck or tank, after you’ve done the ‘split-second analysis,’ if it’s just out on the ramp, think, perhaps, along these lines: GET THE HELL OUT OF THE PLANE!
As for engine or stack damage from the extinguisher? In a word: SHEESH!
If you don’t want residue damage, there’s really only one choice so far as I know: HALON!
So buck up the extra buckeroos for a better extinguisher–metal, people, not that smallish, fits-in-your-kit-bag type of mini-halon, at least not for PRIMARY USE!
It’s good if you can prevent the fire from getting to the wing tanks–and god-awful important if the plane is near any of the aforementioned, flammable objects, but if the fire is spreading rapidly, engulfing the seats and everything else, again, in a phrase: GET THE ‘ELL OUTTA THERE!
So much analysis, less action. And people wonder why stupid pilots die!
I was a student way back in my early twenties, and he–and the rest of his diploma mill staff–were a bit weirded out when I got on my back, laid under the nose-wheel of the resident 152’s, gave the underside of the engine an eyeball, and stuck my arms and hands up inside to give the engine mount firewall nuts a good going over to see if they were loose.
That’s the problem with 152’s: Unlike their Piper and Beech counterparts, one can’t just open the bloody cowling! Bad design, so far as I’m concerned.
Anyway, ’nuff said! –Firefishe
By “he,” I meant, my then-instructor.
Fuel vs electrical fires. Fuel Burned freely (not under compression) will produce black, sooty smoke. Electronics will generally produce white/gray smoke. Also smells are different. You can make your desicion on these indications, but if the smoke becomes thick in the cockpit GTHO. Or exit the AC in an expeditious manner. Smoke of any kind can incapacitate you in a hurry.
That’s good info. Thanks.
Ray is right: Hot electrical wires have a definite plastic burning smell. I’d differentiate an electrical fire by smell alone in most cases. If you’ve ever burned plastic insulation to clean off a wire (not the best way) or dropped a spatula onto a burner you know what that smells like. I’ve never had a fire in the airplane but have had electrical shorts that caused just such an odor in the cockpit.