Fire warning light

121 Operation here. Recently we had a line aircraft with a supposedly "erroneous" overtemp (fire) sensor going off on the ground on one engine." Common with a heavy tail wind, but not expected during normal ops. The sensor is there, but installed for a previous system that is now removed. Prop brake. Anyway, people ignored it until is sounded the red bells on my takeoff one day so we aborted. Our mx wanted us to MEL the system and depart with that bell going off, and we requested a mechanic look at it. Mechanic found a large problem in there, a pipe that was suppose to vent very hot engine air out the side of the cowling, was disconnected. So I am guess we were fairly lucky that the events took place as they did. I later found out that he warning system was inhibited in the air. No other engine or system indications presented.

Yeah Nacelle vents are pretty important.

The Saabs were famous for false Tail Pipe hot warnings if they sat in the rain for extended periods.

I like that. Thanks for posting a good acronym for this type of situation.

I will be quick to caution, in this day and age, turbine engines with advanced fadec systems may compensate, and mask issues that you would normally see in an old fashioned motor.

The fadec will do lots of things, close bleeds, add fuel, etc to maintain normal operating paramaters. Example, our Q. Nothing exceeded normal paramaters until they started melting things off the engine, and then it was things like the fuel flow indication. The motor was, for all indicated paramaters, doing "just fine" by the fever check, the crew wouldn't have done much of anything until the indications started failing... and that was a fair amount of time after the initial fire warning.

This is why you will see 121 guys say, shut it down. Sure 90% of the time there is no problem. But lets say you get te 1% case, and you let it burn until other stuff starts to mess up( because there were no other indication). Perhaps, one of the things to take damage is the main gear that's sitting right next to the engine (and on fire). You put the plane down, gear fails and you hull loss a brand new $30 mil. plane. The cp is going to ask 2 questions. Did you run the checklist? What did it say to do? Manuals, I'd and jepps by my door please.

Much shorter is, did you run the checklist? Yes we secured it and landed singe engine. If te engine wasn't on fire, guess what? You followed SOP's, ran the appropriate checklist, and did so in a manner that complies with your training. Its now on the fleet manager, manufacturer, and mx to determine why there was a false indication and fix it, or come up with better guidance.

System knowledge is huge, but, IMHO, during a potential emergency is not the time to suddenly get creative if there is no need. Do as your trained, and make it somebody else's problem on the ground. Despite what anybody here says, I bet every one of the 121 guys here will shut down the engine if they get a fire indication in flight. Nobody wants to find a new career that badly right now.

Now, a small, light twin where you don't know if you will climb etc? I would prob. Spend some extra time making sure it was burning.

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Yep, from another Dash Driver, WHAT HE SAID...

Mike makes a good point and I agree we should follow SOP and company procedures but those only get you so far. There are times you may need to consider deviating from those in the interest of safety. Knowledge is power.

Eg smoke in the cockpit can be up to 30 minute checklist to run. It may just be safer to just land the plane.

The Bird I fly doesn't have fire detection. So if things go wonky, that Acronym is a perfect thing to have in the bag.

By all means, do what you have to do, I just don't want to spend a month in the jumpseat because some prodigy decides that cycling the battery master and bus fault reset to reboot the fire protection system is better than running the checklist

If its really on fire, you're going to know, especially in a turbine twin with all sorts of goofy systems.

Frankly, I'm not going to kill an engine if I can see its not on fire, and I have no other indications like that in FEVER, or anything else abnormal. I've heard it said that there had never been an inflight fire in a PT6, in fact, they're so reliable, that the airforce removed the fire bottles from some (maybe all?) of the C-12s they have. If I'm the first, I'll be surprised, and if I'm the first I should have a little time to verify that the thing is onfire before I ninja hands the condition lever blow the bottle.

If you go back an read through the posts in the thread again I think you will change your mind as there are examples of fires that were not noticed immediately, or by a fire warning. If an engine is producing power but on fire and I am below acceleration height it is going to keep running until I get there, but as a pilot for a 121 carrier I am going to run the SOP and shut that bad boy down when I get there, or any other time it happens above AH. No one has ever been fired for following the book, as far as I know no one has died either. I am going to follow the SOPs until I come across a situation that it doesn't cover, or a situation in which I don't have time to pull the book out on, like God forbid, a dual engine failure at low altitude.

I've flown the 1900 on one engine for a bit... we still did 180kts at 15,000 feet, and we weren't pushing it. shutting one down in that is kinda almost a non event. The reverse flow design of the pt6 in almost every application (piaggio is differnt i think) generally means that the running engine will "deal" with most fires, the problem could be with compressor section heating if you have a burning leak etc.

I guess I should clear that up...

Being that the PT6 (on the 1900's) actually intakes from the rear of the nacel, and actually just takes in air that is in the nacel, if something were burning, it is highly probable that the ignition source, and all of it's byproducts (heat, smoke,ash etc) would be quickly injested and evactuated by the PT6. I Doubt that the enviroment inside that nacel is capable of supporting most normal forms of combustion. There is simply too much air moving though there to ignight. Now, say you had a fuel leak, which cought on fire in the nacel, I'm sure most of it would really just get sucked into the engine, where the compressor is going to heat the gasses up to 700+ deg c anyways.

I would think that the only issue, would be fuel in the compressor burning, possibly overheating the compressor section, and passing hot gasses into the combustion chamber and or turbins.

So yes, I would agree, the design of the intake and nacel on the 1900's in theory should be very prohibitive to igniting, and continuing burn of a fire.

Thought this may be a good enough topic as any to post this question.
Me and a coworker has a bit of a discussion going on as to the fever acronym used for the pt6 on the grand caravan. Especially the itt part.

My arguments for:
- there is a big chance that the engine itself will ingest the superheated gases and by that result increase the ITT.
- something gets messed up by the fire or it melts the probe itself (it protrudes from the engine itself).

Here are the arguments against:
- If the PT6 gets a fire, it will be outside of the combustion chamber. So, no indication through ITT.
- The air intake is shrouded from the inside of the engine. Also, the ITT probes are between the turbines and have no contact with the engine compartment.
- The FCU temperature compensation section would schedule less fuel as warmer air is less dense.

Any thoughts?