REFLECTOR: Fire Detection Systems

[Chuck Harbert]

I've had 2 inflight fires in my Velocity before I took out the rotary 
engine, and worked as a fire protection engineer for many years, so I thot I 
would throw out my 2 cents on what I learned.

Someone asked about UV detectors and yes, they don't work on smoke. The 
industry uses ionazation (aka products of combustion) detectors which will 
do both flame and smoke.

Plastic pushers are different i.e.the fire/smoke is behind you, but you may 
not know it until it's too late unless you have an indication from a sensor 
(I have a under cowl temp sensor in the outlet). My fires were from ruptured 
oil coolers which the tower saw at takeoff, so I was able to return to the 
field quickly before the engine quit. Fortunately, the fire did little 
damage because the interior of the engine compartment was painted with fire 
retardant (intumescent) paint. I would highly recomend you do this 
especially to your wing roots. I heard a recent story about a Velocity that 
was on fire (engine oil, I think), but it burned for quite awhile (maybe 30 
minutes) before the pilot knew it. I'm not sure of the outcome. Maybe 
someone else knows the whole story.

Halon (which is now banned due to ozone damage-Montreal Protocol) is an 
excellent fire extinguisher for most fires, but it needs to be contained to 
maintain the concentration, and you can breath in it. I have a small halon 
hand extinguisher in my cabin that I could use for an electrical (or other 
types) fire if I could spray it near the fire. They warn against using it 
for deep seated fires, but I don't think we need to be too concerned about 
this.  They now have a couple of Halon substitutes, but they're very 
expensive and take twice the volume. I think the only possible application 
is in the cabin area where there is limited airflow in and out. The engine 
compartment would have way too much airflow to hold any concentration of any 
extinguisher.

Anyway, the point is, I think that a plastic plane should last for quite 
awhile before it structurally fails, so having some type of fireproofing and 
detection is a good thing and might save your life.

Chuck H