Fire indicator??

[keen9a]

https://www.meggitt.com/products-ser...eat-detectors/
The pneumatic detector pictured is a tube, but they make ones that look more like wire, and are generally referred to as fire-wire.

[Paul 5r4]

Very well said Mr. Bill Boyd!

[Desert Rat]

Fire warning systems certainly have their place, but in my experience where they are really of significant benefit is on a multi engine airplane with engines out in an area where they may be on fire for a while before you'd otherwise notice it.

Single engine in the front, it would be pretty hard for me to justify adding a fire warning system for any reason other than it' kinda cool. But again, thats just my opinion.

Having said that, I'm a guy who's installing a remote start button on the stick, a taxi camera under the wing, seat heaters, etc.etc.etc. So I certainly get the attraction of more gadgets.

[ZAM]

Yep, overthinking it, but anything is better than getting back to my taxes.

Executive Summary: Would a temp sensor /loop enable me to turn an inflight fire event into an inflight overheat event? IDK. Maybe. But I think I'm gonna run some temp sensors FWF anyway.

****
Long version:

It is helpful for me to think about what precisely we mean when we say "fire detection." We are likely talking about OVERHEAT detection. Overheats can lead to a fire. Fires are proceeded by an overheat. Fire detection is just a sub-range within the overall range of sensor heat detection where things in your FWF start to change state.

With this in mind, I am pondering the following:

-Are there a meaningful number of scenarios in which a pilot could avoid an inflight fire given instrumental evidence of rising and/or excessive heat FWF (but no fire, yet)?

-Do I really care if there is an actual fire FWF if the temps are "much higher than normal"? Which leads me to the question...

-Could I meaningful temp ranges for caution and warning alerts? Ranges like...
"Yes Garmin, Thank you. That's a bit higher than normal, I'll look into it" and "WOW, no doubt that'a $*&@ fire!!"

-Are there redundancy/design elements/procedures that allow for safe continued flight after a "nuisance trip"? If not, am I really gonna treat an indication alone as a fire? A caution? There are HF issues to consider.

These are the some of the questions that I need to answer before installing a fire/overheat detection system FWF.

HOWEVER, the OP got me thinking about adding at least a couple of K-type temp probes to my yet unsealed FW pass-throughs. If for no other reason, I can foresee future tests/projects/scenarios that would make it a good idea to add a couple of cheap probes now vs later. Suspect that your flux capacitor is failing due to heat? move the sensor and check it. Does opening the oil door after flight really help cool that much? You have another data point. And I already paid Garmin for some currently unused monitoring features. Heck, I'm not sure that a pair of unused shielded wires through the firewall now wouldn't be a blessing in the future. I'm estimating a C-note and minor labor for an unsealed firewall?

[Bill Boyd]

Sam I'm not sure I follow your reasoning about fire just being at the end of an "overheat spectrum" (forgive me if I am putting words in your mouth).

Overheat, whatever that is construed to mean, might show in high CHT's, I suppose. Beyond that, what component you are concerned about becoming too hot - the cowl, perhaps?

My vision of a FWF fire is not an event caused by gradual rising of temps to an unsafe level - it's of oil or fuel spraying onto a component that operates constantly above their flash point: the exhaust system. This is a sudden and catastrophic event, not usually preceded by an over-temp in the engine compartment so far as I know.

What type of event are you hoping to avoid by just monitoring how warm things are becoming under the cowl? What are you proposing to attach temp probes to beyond the usual: CHT, EGT, and maybe carb inlet temp?

Thanks for helping me understand where you are coming from.

[Webb]

I’m installing 2 temp probs. Taking action on one in my opinion which is the lowest form of fact would not be a wise action.

For the sake of discussion, if my normal exit air temp is 130 on each probe and doesn’t fluctuate in flight, I feel pretty sure everything is just hunky dory.

If probe one goes to 459 degrees and probe 2 shows 130, then I would not respond and replace the faulty probe.

However, if I have 2 probes that show 450 degrees, then I have confidence I have a problem.

I would much rather take my chances on gliding to a landing instead of waiting and flying a fireball to the scene of the crash.

I can do a restart in midair if I were to shut the fuel off and both probes stayed at 450 even though there was no fuel feeding a fire.

The way I look at it, I have a much better chance of survival than the guy who doesn’t know until it’s too late.

Since I usually travel at 8-10k feet, I have plenty of time to make a decision based off the info at hand and avoid a helmet fire.

That’s the long of it.

The short of it is regardless of how you do it, redundancy is paramount.

That’s my story and I’m sticking to it. LOL.

[ZAM]

Originally Posted by Bill Boyd

...My vision of a FWF fire is not an event caused by gradual rising of temps to an unsafe level - it's of oil or fuel spraying onto a component that operates constantly above their flash point: the exhaust system. This is a sudden and catastrophic event, not usually preceded by an over-temp in the engine compartment so far as I know.

I assume we both would agree that fire progression is often very quick. But me thinking this doesn't mean it is so. I haven't seen hard data on how fires actually progress FWF. Anecdotal evidence may well suggest that SE recip fires go from "not on fire" to "raging fire" nearly instantaneously. However, this could simply be a matter of most pilot's not KNOWING they've been on fire until the fire passes some threshold the pilot is able to sense, like melting shoes, smoke or secondary failures. Does the smell of burning rubber 14 minutes into the flight mean the fire started 14 minutes into the flight? Maybe. I do not know the answer.
I hope this question is more precise: In general, can we rule out with some certainty that no meaningful amount of time passes between "no fire", "on fire" and "raging" fire?

Originally Posted by Bill Boyd

What are you proposing to attach temp probes to beyond the usual: CHT, EGT, and maybe carb inlet temp?

Webb's post above seems plausible.

However, the OP's question is about where to find equipment to build a warning system, not whether one is worthwhile or effective or if I think it makes sense. So I'll put the brakes on my thread creep. If the "why's" are interesting, please PM me and I'll start a thread.

[airguy]

Originally Posted by ZAM

However, the OP's question is about where to find equipment to build a warning system, not whether one is worthwhile or effective or if I think it makes sense. So I'll put the brakes on my thread creep. If the "why's" are interesting, please PM me and I'll start a thread.

My purposes have been served - go ahead and creep all you like, might as well keep it under the thread title that is likely to be searched for.

[David Z]

A coworker had a high pressure fuel line come undone. Started spraying fuel directly onto the exhaust. Three things saved his bacon that day.
1. It was jet fuel (higher ignition temperature)
2. Turbine exhaust is cooler than piston engine exhaust.
3. The engine quit working, so exhaust pipe cooled down quickly.

Had his failure occurred on a gasoline piston engine, there's a very good chance it would have been 0 to inferno instantly. Sure the exhaust pipes on a piston engine will cool down too, but the fire is already started