Engine Fire

I didn't want to sidetrack this thread on floor mats anymore than it already was...
http://www.vansairforce.com/community/showthread.php?t=124675

But it brought up a bunch of good info on the issues involving an engine fire in flight. Yes, there's a very small chance of it happening, but it's one of the things that scares me.

We have done, what I think, is as much as we can to prevent, and mitigate the situation. Part of it is to prevent known tunnel heat issues in the 10, and part for fire issues. One the engine side of the firewall, I covered it with Lava Shield, by Heat Shield Products. This is exactly what the product was designed for. We used stainless steel pass throughs only. Covered them in fire sleeve and once we're convinced the last wires are through, it will get RTV. We even covered most of the wires, tubing, and lines in fire sleeve.
I'm planning on carpet, and of course have looked into the various "Fire Rated; options, even though I know, that's loose term.
The idea of putting a few feet of stainless on the belly sounds like a really good idea. Pretty light, easy to use SS pops to put it on, and once it's painted, you won't even know it's there.

Has anyone installed a remote controlled Fire Extinguisher in the engine compartment? This seems like a very solid idea unless I'm missing something.

Here's some of our heat sleeving:

Any pics of the install process/finish of the firewall treatment? Is the lava shield pretty durable, if it's on the engine side of the firewall? Would be nice to have a product that didn't require another layer to protect it from physical/environmental damage.

Instead of RTV, you might want to consider intumescent (firestop) caulk; more in line with your more detailed heat protection.

I stop short of a fire extinguisher system mostly because of weight/complexity vs odds of actual fire. If I flew at O2 altitudes all the time, I might think differently (significantly longer to find the ground...) Everybody has to weigh risk/cost/benefit/etc for themselves.

Charlie

I wonder how well the adhesive will hold up in a fire, or are firewall mounted items such at the battery box going to mechanically hold the shield in place?

Bevan

Bluelabel said:

Has anyone installed a remote controlled Fire Extinguisher in the engine compartment? This seems like a very solid idea unless I'm missing something.

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Pretty hard to put out a fire with an extinguisher when 200mph winds are blowing through the fire scene.

rv7charlie said:

Any pics of the install process/finish of the firewall treatment? Is the lava shield pretty durable, if it's on the engine side of the firewall? Would be nice to have a product that didn't require another layer to protect it from physical/environmental damage.

Instead of RTV, you might want to consider intumescent (firestop) caulk; more in line with your more detailed heat protection.

I stop short of a fire extinguisher system mostly because of weight/complexity vs odds of actual fire. If I flew at O2 altitudes all the time, I might think differently (significantly longer to find the ground...) Everybody has to weigh risk/cost/benefit/etc for themselves.

Charlie

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It's made from crushed Lava rock, and it LOOKS like carbon fiber, but from my preliminary testing, it will not absorb or hold onto any liquids. It either beads off or just passes right through. And it's taken a beating during the work and shows ZERO signs. It's even hard to drill through (well, noticeable anyway)

Pre and Post Engine Install

Bluelabel said:

It's made from crushed Lava rock, and it LOOKS like carbon fiber, but from my preliminary testing, it will not absorb or hold onto any liquids. It either beads off or just passes right through. And it's taken a beating during the work and shows ZERO signs. It's even hard to drill through (well, noticeable anyway)

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So, you just applied it to the front side of the firewall and bolted stuff on? Or did you cut out around /under anything, like where the engine mounts bolt on?

Fire extinguisher in the engine compartment might be wishful thinking. As Mike pointed out... high winds there. Makes me think of aerial fire fighting. When the winds are howling... the tankers do not even try to get ahead of the fire.
In my experience, which is only one critical situation... I found that time to the ground was the most important. The engine fire in the single I was flying got so hot, so fast... that it burned through the firewall. My shoe laces were melted according to the emergency room doctor. (a pilot also)
We got out in time to avoid most of the injury from smoke. The plane burned to the ground.
Good materials can buy time... and the data presented here is good for builders. Smoke and fumes is much more dangerous than flames.

Mike S said:

Pretty hard to put out a fire with an extinguisher when 200mph winds are blowing through the fire scene.

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Mike, I did think about that, but I see these types of extinguishers available through ACS and others, so, someone's done it. Plus, in theory, all that fast air is going over the top of the engine, through the oil cooler and to the heat muffs. Seems like a fire would more likely be in the area of lower pressure and slower air... right?

DaleB said:

So, you just applied it to the front side of the firewall and bolted stuff on? Or did you cut out around /under anything, like where the engine mounts bolt on?

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Applied it and drilled through it or in the case of the pass throughs, cut out a 1" round area.

Flying yet? Please follow up with reports on whether the firewall through-bolts for various stuff (battery mount, heat muff, motor mount, etc) stay tight or work their way though the material. Even if it must be cut for 'hard point' mountings, it should still provide a lot of time margin in case of a fire. Hopefully, it will help a lot with regular heat, too.

It sure looks like a nice, simple solution.

Thanks,

Charlie

Fire Bottle

I have a fire bottle in my plane. It is tucked out of the way with the activation cable in easy reach. There are two nozzles one above and one below the engine. In an in-flight fire I'm not sure how much good it would do. With the incoming wind so strong, probably would not help. But on the ground engine fire I am quite convinced it will either put out a fire or slow it down considerably.

A few notes....

Remember the old 5th grade science class description of what you had for breakfast? Why, it was delicious coagulated chicken embryo, a side of salted porcine protein, and a nice glass of bovine mammalia lactate....fancy words for a common meal.

Well, "Lava Shield" is good marketing for a rather mundane product, mineral wool, one of the oldest man-made refractory fibers. It's made by forcing melted rock (basalt is common, i.e. "lava") through a spinner head, sort of like cotton candy, although some is probably still made with air or steam jets. The process is similar for glass or ceramic fiber. All can be woven into fabric.

Lava Shield MSDS here: http://www.heatshieldproducts.com/tech-center

All the solid fibers themselves are relatively good conductors of of heat. What makes fiber wools, felts, papers, and fabrics good insulators is the air spaces between the fibers, air being a much better insulator than any solid. For example, dry snow, plastic foams, and the three fibers here (in wool form) are all in the same thermal conductivity ballpark. Obviously the snow and styrofoam melt at rather low temperatures, which makes them unsuitable for the firewall application. Too bad. Maybe we could sell snow by calling it "Crystal HydroOx"

Bottom line? There is no reason to think Lava Shield has significantly better insulation performance than any other woven fabric. There is not much air space (total thickness is only 0.008"), thus insulation properties as supplied will not be high. Firewall performance could be improved with an overlay of SS foil, which is air-tight, reflective to wavelengths of interest here, and allows mechanical fastening. A really good fabric-based insulator under stainless foil (rather than something sensibly cheap, common, and available like 0.125" thick fiberfrax felt), would be 3M Nextel fabric.

Fire bottles: I have no idea if they will in fact work or not in the in-cowl environment. However this may help, a nice illustration courtesy of Fred Moreno for the Lancair gang:



The key is to realize that velocity is low at the face of the engine, and remains relatively low in the large lower cowl volume. My guess is that you would want to place the spray bars a few inches below the cylinders.

But it brought up a bunch of good info on the issues involving an engine fire in flight. ...., but it's one of the things that scares me.
.....
Has anyone installed a remote controlled Fire Extinguisher in the engine compartment? This seems like a very solid idea unless I'm missing something.

Click to expand...

There must be thousands of NTSB (and foreign equivalent) GA accident reports covering various causes.

If engine fires are a significant safety hazard (especially to life), I would think one would find not only a significant % of reports detailing these, but also the causes (fuel? oil? location?) and assist in designing in the mitigation.

From my jet experience, it is sometimes advised to slow the aircraft down prior activating the extinguisher, only doing so after endeavouring to remove the source then waiting a period, and if the cowls have gone, the extinguisher is useless. As above, since the RV engine compartment (unlike a jet's cowled space) is ventilated at ~IAS I suspect the extinguisher material will last in the compartment for a fraction of a second?

On the ground, after shutting down the engine, might be more useful, but you are then just dealing with saving the aircraft, not life.

Fire

The fire risk can be reduced to almost zero with proper construction methods, proper materials and good maintenance. One Rocket fatal, another Rocket close call, both from loose mechanical fuel pump fittings.
Perhaps the most difficult situation to deal with mentally is an exhaust failure. The safe bet is to shut down the engine immediately by turning off the fuel. This will in most cases remove all fuel from forward of the firewall.
I have had two exhaust failures on turbocharged light twins. The first time I flew 150 miles to get home with both engines running. The second time I headed for the nearest airport with the failed exhaust engine at idle. The reason I left it at idle was the temperature was about 110 degrees and I wasn't sure I could make the airport with one engine shut down. Both failures were at the front of the engine, big hole burned in cowl, not much other damage.

A model collector drain

One thing I didn't like about the A model was the welded reinforcement creates a collector for fluids. It forms a cup that could hold a lot of fluid. I drilled holes at the base of the reinforcements to drain fluids should there be a leak. Another option from a builder was to fill it with RTV. Certified engine installations do not allow locations that would collect fluids in the engine compartment and a test is conducted whereby residual fluids are measured to a specified pass/fail limit. This area would not pass the test. The top of the FAB box probably wouldn't pass either unless the fluid could pass around the top plate into the FAB and out the bottom.

See the hole at the bottom of the welded plate. All sides drilled except the most aft plate.

You have done nice job of trying to prevent a fire from coming throught the firewall. But what about the heating duct valves. They are made of aluminum and the flappers are stainless, which means nothing if the housing holding the valve melts away.

Curious what most of you are doing about smoke and potentially dangerous fumes that come along with a fire. Do any of you carry Portable Breathing Equipment (PBEs)? How about those of you that have O2 bottles in the cabin. Are you doing anything to protect those as well?

That might be more of an issue with an electrical fire, with an engine fire that i had 3 yrs ago due to oil starvation and a crankcase that came from the all together at night, i closed the heater and opened the air vents and no more smoke. That was on my mind first that the fumes would get me but i was able to land at an airport still on fire from the oil on the firewall. Diving at 200 mph kept the flames under me until touchdown, then a mad dash exit while trying to not get run over by the fire dept at night. I always did fly a little higher at night

There is no need to guess as to whether or not a fire suppression system plumbed forward will do any good or not. This has been well proven in race cars. Fire the bottle before you come to a halt and 20lbs of halon goes blowing into the wind while the fire rages on. Anyone considering two ten pound bottles for their plane?

An airplane in flight....not a chance at all that a fire bottle puts out a fuel fire. I've been on fire twice in race cars and watched a friend's cars burn to the ground....because he pulled the handle while still moving and two 10lb bottles nearly choked him out (with all windows down) and his expensive toy burned to the ground. This isn't theory, the only thing a halon bottle will do in flight is choke anyone trying to breathe it and that.....isn't as fun as it sounds. YMMV....but I doubt it. Be careful out there....a pound of prevention and all that....

hawker said:

...with an engine fire that i had 3 yrs ago due to oil starvation and a crankcase that came from the all together at night, i closed the heater and opened the air vents and no more smoke. That was on my mind first that the fumes would get me but i was able to land at an airport still on fire from the oil on the firewall.

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Hawker, tell us more please. It is difficult to get good, first hand information about fire incidents.

Aircraft type?

Engine oil fire from a ruptured crankcase?

Obviously the engine was not operating well, but when/how did you know you had a fire?

The fire itself was firewall forward, so what was the source of the smoke/fumes?

Any post-incident photos of the airframe damage?

It was an RV6 with a Lyc o-360 200 hrs on it at night vfr 6,500' about 3 miles from the Hartford CT airport 3 yrs ago. Had a slight vibration, headed towards the airport and a few seconds later smoke came in via the heater duct then total engine failure. Opened the fresh air vents and closed the heater. No idea of a fire until touchdown when the flames were around the cowling, diving at high speed kept everything under me. Oil starvation, not sure where because of the damage caused the rear of the the case to come from the all together. Leftover oil on the firewall kept the fire dept busy but they damaged my prop with a crowbar. Then the fun part of dealing with insurance, they would not total a/c so i had to repair it firewall forward. They do not cover the part that fails IE-motor @$25K. First total single eng fail in my 40 yrs of flying and hope my last. I drive a Hawker jet for a living, only had 1 of those motors fail so far. Glad she is back

I also have grave doubts about aluminum heat boxes. It sort of defeats the purpose of all the other precautions one takes to seal the firewall. I will redo mine on SS. Maybe I'm dreaming and it is only my imagination but it seems to me to be a glaring inconsistency.

Apart from that I think the best prevention is to have the cowls off often and check all the fuel fittings and exhaust system. That and a little luck never hurt anyone.

Cabin Heat Box

Several different versions of the all stainless heat boxes are available from Aircraft Spruce.
The company that originally designed and manufactured these boxes also manufactured the tube style firewall pass thru kits. I believe the company has since been sold but still in business the last time I checked.

Stainless Steel heat box

I have the originals (so original I worked with the gentleman that owned planeinnovations.com, Paul Bowmar to create the one for the RV-10. When he designed them he designed it to assure there was a tab on the doors to seal the stainless steel. He actually used a torch (and caused a fire in the process) and the heat boxes remained solid with no smoke /melting, or issues.
Another issue I have heard others mention that I do not have a problem with- tunnel heat. My tunnel is not hot to touch, another point that the SS box does stop any heat from getting through.
Sadly he passed away a couple of years ago in a plane accident, but the company remains as solid as before.

Pass thrus

Aircraft Spruce also has the stainless pass thru. A bit pricey but the kit includes some fire sleeve and a tube of sealant.

krwalsh said:

I have a fire bottle in my plane. It is tucked out of the way with the activation cable in easy reach. There are two nozzles one above and one below the engine. In an in-flight fire I'm not sure how much good it would do. With the incoming wind so strong, probably would not help. But on the ground engine fire I am quite convinced it will either put out a fire or slow it down considerably.

Click to expand...

Does this spray for a certain time period (15 or 30 seconds?)