FWF-Insulation glue !

[L.Adamson]

Originally Posted by Wicked Stick

How much of a real engine fire is this simulating ?
What I mean is, how long do you think it would take before the firewall would reach the same conditions as your burn test did ?

That's my question. I can assume that most of an engine fire is going to be "oil" only, as a fuel. I'll also assume that I'll be smart enough to turn the fuel selector off.

Question is; will engine burn like a blow torch when much of the oil is still in the lower pan? I deal with flames and furnaces daily, as part of my job. But I haven't got around to setting any Lycomings on fire with 100+ mph fans blowing against them. I must really wonder if an engine burning residue oil is going to get a stainless steel firewall hot enough........fast enough? The oil would have to be spraying or atomized to get up to these high temps........IMO.

edit: In fact, until I see definate proof than an "oil only" fed engine fire is going to wrack havoc on the firewall------------I think that some of us are overreacting to the use of certain materials in the cabin.

L.Adamson

[L.Adamson]

After 38 years in the heating business, and seeing vertical and horizontal gas fed flames, day after day...

I just don't believe that a propane fed test stand blowing flames against a stainless steel firewall, is what we're going to see from an oil fed engine fire against an RV firewall. My 100L fuel line will be "off".

Modern oil furnaces work by atomizing the oil into a fine spray. Is the none running aircraft engine going to do this? Will the oncoming airflow
through the cowl inlets atomize most of the oil as it sits engine engine pan? I don't think so!

Nope, I don't buy it. The test is more like using my oxy/ace for silver-soldering refrigeration lines. Those fittings can glow red from the intense heat, and will ignite materials rather easily.

If the engine compartment is really that hot, then I believe the cowl and windscreen will be vaporized too. And I think we'll be toast before the firewall turns cherry red.

One note here: The black rubbery material that covers refrigeration lines was mentioned somewhere in these threads. Might be under the name of Armaflex as well as others. That stuff can actually be right next to the cherry red fittings, and it will just usually start burning on the edge, and can easily be blown out. It really is on the high side temperature proof!

L.Adamson

[Mike S]

So, if a product can stand up to the propane test, we will have a pretty good safety margin.

I seem to recall that the 2000* test is what the fed/far standard is, anybody confirm this??

[DanH]

Yes Mike.

A good place to start is FAR 23.853 "Passenger and Crew Compartment Interiors":

(f) Airplane materials located on the cabin side of the firewall must be self-extinguishing or be located at such a distance from the firewall, or otherwise protected, so that ignition will not occur if the firewall is subjected to a flame temperature of not less than 2,000 degrees F for 15 minutes.

Other good sources are the "Aircraft Materials Fire Test Handbook" or AC-20-135. In addition to the 2000F requirement, you'll find most test specifications suggest a heat transfer rate around 10±1 BTU/ft sq per second.

Want to see what that looks like? This is a photo of a burn test underway at the NAVAIR Aircraft Fire Protection Test Pad Facility, Patuxent River Naval Air Station:



The above burner is the FAA-standard Park DPL. My own little homebuilder burn rig is easily calibrated for 2000F at the firewall surface, but I don't have a calorimeter. Is the propane torch pumping out more BTU's than the Park burner? I kinda doubt it. At 70F, about 35,000 BTU's per hour is the maximum for a 30lb propane cylinder. That works out to be 9.7 BTU per/sec under optimum conditions...total BTU. Not all of it is getting to the steel surface.

I don't know how and why "2000F and 10 BTU/ft sq p/sec" became the standard. I figure the FAA, Navy, etc must have some reason; apparently engine compartment fires do get that hot.

Maybe RVs burn cool <g>

[Pilottonny]

What material will cope with this kind of heat? Certainly not the cowl and the windscreen. Any suggestions for a firewall insulator, that will?

Regards, Tonny.

[L.Adamson]

Originally Posted by Pilottonny

What material will cope with this kind of heat? Certainly not the cowl and the windscreen. Any suggestions for a firewall insulator, that will?

I discussed this with my son in law who is a fireman yesterday. If we get the firewall protected to 2000 degrees, then the canopy and cowl will be like a firemans face mask.........gone before the rest of their suit. He also agreed about the oil fed engine, as long as the fuel is shut off.
And, if it's that hot, we're most likely out of it (so to speak) before the interior goes up. The point is to make sure the fuel supply is off, and firewall penetrations are plugged for smoke.

L.Adamson

[CRW]

I have been reading this thread with some interest because I am at the point where I would like to insulate my firewall. Many years ago, I worked in an industry that did heat treating. Most of the heat treating was done in the 1600 degree F. to 1750 degree F. range. Occasionally, we did treatments in the 2,000 to 2,200 degree F. range. When we took the furnaces to the 2,000 degree range, the maintenance personnel got in a bad mood because the furnace had to be re-built after these high temperature runs. Even the furnace refractory could not stand this temperature indefinately. So far, based on what I have read here, there is no glue and no insulation material that can meet the 2.000 degree requirement and be suitable for airplane use. I pretty much know what NOT to use.
I still have the question of what to use.
Please give me a list of what insulating materials are acceptable and which adhesives are acceptable. If the 2,000 degree test can not be met, then what can I reasonably expect from the best alternate?
Regards,
Chuck

[DanH]

Ya'll are missing the point.

The goal is to survive an intense fire for perhaps one minute, or a low intensity fire for maybe 5 minutes. Survival requires no flame in the cockpit, low smoke, and low radiant heat levels. A plain uninsulated firewall will satisfy the first two criteria, but fails big time on the third. When we select an insulation to reduce radiant heat, we want one that doesn't compromise the first two.

Using a burn rig believed to be less intense than the FAA standard, the insulation tested a few posts back burst into flame in less than 15 seconds, while emitting large quantities of black smoke.

The point is to be very cautious about anything you place in proximity to your firewall.....in particular paints, coatings, and glues, and most certainly "firewall insulation" which turns out to be totally unsuitable for a firewall....regardless of how advertised.

Are there insulation materials which will withstand the one to five minute criteria? Yes, of course. The rig in the photos was assembled to check materials intended for my own RV-8. The best candidates so far trend toward a ceramic fiber with a reflective metal backing on the cockpit side (no surprise). I've been spending my time building, and I've not yet had the chance to run comparisons on all the choices. When this thread arose, I offered to test Mike's material because it was on the list anyway. I'll be happy to run other materials if you want to send them.

You think the FAA criteria was set without basis and the results are invalid? Fine. Ignore them.

[JonJay]

I think your points are very good Dan. I think it would need to go way beyond the firewall, and may not even be possible, to protect to this level. Most of the deadly fires I have heard of where post crash and probably not survivable regardless. I have not heard of any RV in flight fire accidents but there may be some, and nobody wants to be the first for sure.
I do know that my Aeronca would not have complied nor my Bucker. Of course with my Bucker the fire has to burn through my passenger before it gets to me. Ha!

[Mike S]

I know the original post on this thread was about adhesive, but the thread has "evolved" more than "drifted", IMHO.

Considering Dan H's last comments, I think it is time to revisit this thread