The best fire suppression system is just plane water.  Before I retired we replaced all of our CO2 fire suppression systems with high press. water mist.  30 gal of water replaced 6 150# CO2 bottles.  The idea is the water will spray out in a fine mist and instantly turn to steam, this removes the heat from the combustion and also displaces the air.  I know that displacing the air would be hard to do in a moving aircraft but removing the heat would definitely put out the fire if the mist were spraying on and in the area of the exhaust this may prevent what ever fluid is leaking from re-combustion.  A high press. water system big enough to be able to do this would be weighty and take up a considerable amount of room (Water container + high press. gas cylinder plus high press piping and spray nozzles.)  I am not sure how to figure the  btu's stored in the exhaust system, but fairly sure that it would be a function of the mass of the eshaust system and the temp. of the metal, this would dictate how much water would be neede to remove this heat.  Water would have to be kept above freezing, this throws another kink in the logestics of this type of system.
Somone out there may have an idea on this and how to make this a practical system.

Bob P.

-------------- Original message from Todd Bartrim <bartrim@gmail.com>: --------------

Hi Ed;
    You're most likely right on the money, about what would happen, however I guess I'm just hoping that if it ever happened, a few more minutes might be enough. Long ago I ran a 3/8" tube with a 1/8" hole every 3" from the firewall, following the path of my fuel feed line. The other side of the bulkhead fitting was a hose that connects to the cockpit fire extinquisher. I replaced the little plastic nozzle with a tube fitting. The hose is only on there finger tight, so can be easily removed for normal use, but if connected to the hose it should fill the engine compartment with dry chemical suppresant. Sort of a poor-mans engine bay fire suppresion system. Never tested it yet, mostly because I don't want to clean it up afterwards, but I'm thinking maybe I should come-up with a mock engine bay, start a small controlled fuel fed fire inside, use a pair of leaf blowers into the intakes and see how well it works. A bit of work to do something that would be representive of an in-flight fire, but it might be fun!

Todd
C-FSTB
RV9 13B

On Thu, 2009-07-02 at 21:36 -0400, Ed Anderson wrote:

Hi Todd,

 

Certainly the horror  of in-flight fire is something aviators have faced since WWI.  I commend you on your effort to minimize any FWF combustion event (other than inside the engine).  However, I must tell you I have some doubts about the protection you may think you are getting.  This comes across to me more of a heat shield kit than a fire shield kit.  Here are some of my reasons for  why I believe you may not be getting the protection you think: