fire warning

[Charles Davis]

Has anyone tried to install a fire warning system in your cowling?

Just something that would turn a warning light on if the temperature got too high.

[wvshoem]

I read about a fire detection method I thought was quite clever. It may have even been here.

It involved wrapping an insulated wire around the engine in key places (where ever those are) so it is in contact with metal surfaces. The circuit is connected to power and a light on the panel. The theory is that if there is a fire, the insulation will burn away and the wire will come in contact with the metal on the engine, completing the circuit and illuminating the light on the panel.

The failure point I thought of when I read this was the wire could chafe over time and eventually give a false warning. On the up side, this system would cost about $6 for materials (LED and wire).

Just a thought.

William

[Charles Davis]

That is really very clever!

I'm not sure how important fire detection is, but I know there have been some tragic accidents lately, and with the engine in the back, some sort of heads-up (even if you get some false reports from time to time) would seem useful.

[D]

Charles -

Bill James installed a variant of the "melt through" fire detection on his Vari (a 2 wire pair w/ one lead hot and the other ground connected to a warning lamp).  There are a bunch of pic's and details about his airplane here:

http://www.ez.org/feature/F0502-1/F0502-1.htm

Neat guy, with a bunch of neat mod's.

D

[fpullanojr]

How about a totally different method but with a quicker warning and possibly a more solid indication.  I would think that there is a possibility that a couple of things might go wrong with the insulation to ground method mentioned above.  First of all, if it got hot enough the wire could fail thus opening the circuit and NO WARNING at a bad time.  The ground with insulation could fail if the ground moved away from the conductor so unless the ground would wrap around the entire wire...

Just food for though but here's another way.  You take a low amp 12volt relay that is normally closed.  You use the current on the system to hold the circuit open with a test switch to close the circut and test the warning system.  The trick would be the "fire loop"  That conductor would be .040 solder or a similar type of material.  As long as the low current on the conductor doesn't melt the fire loop it maintains the closed circuit and keeps the relay energized.  If the engine bay gets HOT, that solder would melt away and allow the relay to de energize and thus close the fire loop warning circuit. Buzzer, Lights etc.  This way the system is designed to indicate a hot bay at the failure of the conductor unlike doing it the other way around where the indication requries an "in tact" conductor.

It's a wag but it might work that way too.

[GlennBob]

Some guy recently had pics of his method.  He took a unit from a clothes dryer.  It is either a fire detector or a dryer overtemp indicator.  The picture shows it mounted on top of the engine. Then he has it wired to a light on his panel.