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For the reasons Scott stated, I think Halon is a poor choice for this application. It will probably knock the fire down initially, but fire is likely to reignite from the residual heat as soon as the Halon is flushed out of the engine compartment. If you want an engine fire system, I would recommend a dry chemical agent.
I have personally investigated numerous marine engine room fires where Halon or CO2 were used to extinguish the fire, only to have the doors left open, or reopened too early by curious crewmen. The fire is quickly knocked down, but with the addition of fresh air, it quickly reignites and burns out of control as there is no effective suppression system left to utilize. The cowl inlet on you aircraft will ventilate the engine compartment much faster than an open door on an engine room.
Halon is primarily used for inhabited spaces where you don't want the occupants to stop living. Otherwise, CO2 is the cheaper effective choice. The only reason I can see to use halon over CO2 outside of the cabin in an airplane is that you don't need nearly as much, hence it weighs less.
For what it is worth, Halon differs from CO2 in that it does not deprive the fire of O2. Instead, it chemically bonds with the free radicals which are part of the chemical chain reaction of the combustion process. This is why Halon can be used in confined spaces with people. CO2 lowers the O2 concentration and suffocates the fire just like it suffocates animal life. Pilots generally crash shortly after they die, so if you want to use Halon, put it in the cabin and keep the windows closed.
Rob
In a message dated 01/13/10 10:15:46 Eastern Standard Time, sky2high writes:
Valin,
Most engine compartment fires are from an oil or fuel leak. If the engine continues to run, ignition sources from heat (i.e. exhaust pipes) still exist. Air is plentiful and flammable material may still be available - fuel can be shut off, oil cannot. So, even though you have a fire suppression system, the engine must be stopped and fuel to the engine compartment must be shut off before the fire can be extinguished.
Halon deprives a fire of O2 but a Legacy descending at a high rate of speed will flush out the Halon as soon as it is released. Perhaps too much air will upset the A/F ratio and kill the fire. Remember that ground bound applications generally assume that the vehicle will quickly come to a stop thus increasing the effectiveness of a Halon type suppression system. Hmmmmm, no fuel shutoff in a car except for killing power to the fuel pump.
The system would work perfectly for a fire whilst taxiing.
Scott Krueger
PS The standard 300 series fuel shutoff is at the aft bottom of the header tank. For me, operating solo, that would require loosening the shoulder straps, leaning forward and way over to the right to reach the shut off - thus losing all flight visual reference. The following aerobatic maneuver could be interesting while I must quickly sit up, recover and re-tighten the belts - hoping that the fire will blow itself out. Ahh, fire is bad.
In a message dated 1/13/2010 7:20:14 A.M. Central Standard Time, thorn@starflight.aero writes:
Hey LML gang,
As part of our risk management strategy, we want to install an engine fire extinguishing system in our Legacy under construction. We’ve zeroed in on this Halon 1301 based system from Safecraft. See screen shot from Aircraft Spruce’s website:
We’d appreciate comments and advice from the community regarding choice of systems and installation recommendations. Some specific questions are:
· Would a single 5 lb bottle provide enough Halon concentration to extinguish an in-flight fire?
· Do we need to route discharge lines to the cowling inlets to ensure we’re getting the Halon throughout the compartment when discharged for a fire?
· Has anyone had an engine fire that was successfully extinguished in flight?
· We’re trying to eliminate mechanical connections to the instrument panel to make it easy to remove for maintenance (eg. No push pull cables, etc.). Anyone have experience with setting up for electrically actuating a system?
· Etc.
Thanks,
Valin Thorn
Legacy
Houston, Texas
Starflight, Inc.
1702 Emerald Lake Ct,
Houston, TX 77062
281.486.4663
http://www.starflight.aero/legacy
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