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Fire suppression systems, worth it?

agent4573

Well Known Member
Does anyone use a fire suppression system in their RV? Planning on a 7 build that will be used for some entry level acro competition before we get a dedicated acro plane. Was planning on doing the Ti firewall and belly pans, but wasn't sure if a suppression system in the engine made sense. Bottle would be mounted behind the seat. A few questions:

There's a few Halon replacements out there, one is a cold gas type that I want to avoid because it will likely supercool the cylinders and cause engine damage. The other options are a gas or aqueous foam.

Is Halon gas effective in an engine bay with as much airflow as the RV cowl? 3 nozzles come with the kit, plan was one on the battery and one on each side of the engine.

Should the engine nozzles be under the engine aimed at the exhaust or on top of the motor so it gets sucked through the fins and dispersed as it flows down? Should they be on the front of the plenum faced towards the firewall or on the back of the motor facing forward?

If anyone has worked an acro team or a reno team that used a suppression system, any details would be great. Can't find much info on Google. Thanks.
 
one is a cold gas type that I want to avoid because it will likely supercool the cylinders and cause engine damage.

I have no idea if any of these systems would work on an aircraft engine such as an RV, but...

If I'm on FIRE, the very least of my concerns would be engine damage due to cooling from the fire suppression system.

As a wiser man than me once said:

"How much does a new engine cost?

Not as much as a new behind."
 
AFFF

I installed a fires suppression system in my (non-RV) plane. But I did it because it is a pusher configuration and it is much more difficult to know if you have a fire situation until it is probably too late to simply shut off fuel and master and hope it goes away. Realistically an AFFF system has little to no chance against a 200mph wind going through the cowl. On the ground I think it would be much better.

The race car suppliers all have good systems that are relatively inexpensive and lightweight. I hope to never find out if mine is effective.
 
A desire that systems not needlessly damage your aircraft and recognizing your life takes a higher priority than a machine are not mutually exclusive...
 
I have no idea if any of these systems would work on an aircraft engine such as an RV, but...

If I'm on FIRE, the very least of my concerns would be engine damage due to cooling from the fire suppression system.

As a wiser man than me once said:

"How much does a new engine cost?

Not as much as a new behind."

True. I was hoping it would be possible to cover a battery fire situation without ruining a perfectly good motor though. I think my biggest concern though is how effective are any of these systems in at 75 knots? I can likely get to best glide speed before pulling the fire handle, but I don't know if any Halon is effective with that much air flow through the bay.
 
A desire that systems not needlessly damage your aircraft and recognizing your life takes a higher priority than a machine are not mutually exclusive...

True, and I hadn't considered the idea of putting out a ground fire (but the case mentioned, a battery fire, may not be stoppable without a means of cutting the electrical circuitry driving it). And the OP seems to be talking about fire in flight, not on the ground (on the ground, pull the mixture to ICO et voilá! No more airflow, so the original question is moot).

As far as damage vs. safety-of-life...BRS seems like a case in point one way :).
 
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In an engine fire you will likely turn the fuel off and have the nose poked down in a max rate descent. Your priority should be to get on the ground as soon as possible and exit the aircraft. Bleeding speed just to activate the suppression system is a bit of false economy. The beauty about the belly/firewall insulation found elsewhere on this site is that it will help buy you some time during the descent.

Alternatively, buy a parachute, insurance and put pull pins on your canopy to make it easily jettisonable.

Tom.
RV-7
 
Is Halon gas effective in an engine bay with as much airflow as the RV cowl?

There are a few ways to look at the question. Perhaps one is from the standpoint of mass flow. The Lycoming charts suggest most RVs are flowing 1.5 to 2 lbs of air per second. Let's go with 2 lbs to make it easy.

Halon replacements seem to require a concentration of 600 to 900 grams per cubic meter. I'll use 900 for this example. There are 35.315 cubic feet in a cubic meter, so the required concentration becomes 900/35.315 = 25.5 g/ft^3.

At 1000 MSL, standard day, 2 lbs of air is about 27 cubic feet. So, to reach the necessary minimum concentration of fire suppressant, you would need to discharge about 700 grams per second, or roughly 1.6 lbs if I have not screwed up a term somewhere. It would be a little less at a higher altitude.

So what is the required concentration, capacity, and discharge rate of the system you're considering?
 
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Alot

Thats a lot of stuff to discharge. And assume this has to stay around long enough to prevent re ignition, seems like it might not be practical unless source can be quickly eliminated.
 
Ground Fire

This was the specific case I was thinking of when I bought my fire suppression system and installed it:

http://www.deford.com/cozy/fire.html

Granted, I took other lessons from this, including making sure firewall pass throughs were either fused, connected to battery contactors before the energy source got to the firewall, etc.
 
So what is the required concentration, capacity, and discharge rate of the system you're considering?

Well that is the question. I found a few old military reports on Halon concentration requirements, but couldn't find anything published for the replacements. I don't doubt your numbers of 1.6 lbs/sec, and the systems I was looking at were 5 lb bottles that sprayed for <10 seconds. There's no way they would be effective unless I was stationary on the ground. That's ok though, I'll do up the firewall insulation and Ti skins and call it good. It'll save me 10 lbs for the system install anyway. I've read your posts on the firewall fire proofing many times, but can you post a link to any info on a belly plate? Thanks.
 
Well that is the question. I found a few old military reports on Halon concentration requirements, but couldn't find anything published for the replacements. I don't doubt your numbers of 1.6 lbs/sec, and the systems I was looking at were 5 lb bottles that sprayed for <10 seconds. There's no way they would be effective unless I was stationary on the ground. That's ok though, I'll do up the firewall insulation and Ti skins and call it good. It'll save me 10 lbs for the system install anyway. I've read your posts on the firewall fire proofing many times, but can you post a link to any info on a belly plate? Thanks.

Paul,

Two lbs/sec cooling flow and 900 grams per m^3 are rough worst case estimates which assume cruise speed, and a Halon replacement requiring roughly double the concentration. And you should not take them as gospel; I was merely thinking out loud. ;)

Appears to be some good data here:
https://www.fire.tc.faa.gov/pdf/11-31.pdf

A few belly overlays here:

http://www.vansairforce.com/community/showthread.php?t=158579
 
...difficult to know if you have a fire situation...
I had the same concern so installed a cheap digital meat thermometer with the probe sticking through the firewall just below the oil cooler. I also installed a 3/8" bulkhead fitting on the right side of the panel leading to a spray bar across the top of the engine compartment above the fuel lines/pumps. My Halon fire extinguisher nozzle fits right into the bulkhead fitting. I have no idea if it would work when needed and hope never to find out.
 
Check this out. I?m considering it for my new build.

Www.proteng.com

It is currently installed on EAA?s RV-6.

I looked into those systems as well. The large warnings on the website say "this is a total flooding agent" and "used in confined spaced, not for outside fires". That says to me, it would be completely useless while the airplane was moving and generating any type of airflow through the cowl.
 
My vote would be for no. In fact my IAR823 (Romanian Exp) has a pressurized cylinder on the firewall with nozzles that have a burst tip to do their thing. I pulled it off.

In my race car I've had 7 fires and used every type of agent available. By the time you detect fire I assure you there is enough damage done that the wiring is usually toast and the engine is coming out either way.

In my "big" fire (video available) I detected fire at about 80mph and by the time I came to a stop it was raging (similar to a takeoff scenario). I had 5lbs of AFFF plumbed into the engine, and 5lbs of Halotron also plumbed into the engine and an additional 2lb Halon handheld. The fire kept on going despite deployement of all of these in the closed engine bay. Finally after a minute the fire crews arrived and one quick shot of an ABC dry-chem later it was all done.

AFFF foam seems to do pretty well if you happen to have the nozzles pointed at the problem and give it some time to do its thing.
Halon and Halotron seem to need an enclosed vessel to get their business done.

ABC does have a melting type agent in the "A" part that makes a mess but lordy it sure knocks fires down. They do make a BC only which should wash out easier but I haven't used that particular one.

Another thing I like about a simple handheld (dry chem is my weapon of choice) is to remember the fire might not be you! You could roll up to an accident on the taxi-way and use it to help remove some occupants or many other scenarios. I know nobody likes dry-chem but it has never once let me down and unintended fire is really attention getting.

My .02. (Edit: Extinguishers are a personal choice so do what makes you sleep well. Any is better than none. My opinions come from specific personal experience and performance background)
 
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