firewall material

[Eric]

Hello

What matrial do You all use for the firewall?
Mine(kf 3 1991)is made of aluminum.
I don't think that is very fire resistant?
I am thinking of making a new one from stainless steel(0.3mm)

Are there other sugestions

thank You

Eric

[Dorsal]

Mine is SS (not sure of the thickness) which I believe is the current standard.

[Av8r_Sed]

My Model III is about the same age (SN 910) and has a stainless steel firewall.

-- Paul S

[rogerh12]

Eric;

Galvanized steel is very popular too. It's cheaper and certainly easier to work with then stainless steel, and if you screw it up, you’re not out much money (most folks have to special order large stainless sheets). Also, keep in mind the word "stainless" actually describes a large array of types. All the way from Chromium /steel (like used on steak knives) to Nickel/steel (like used on pots and pans) , and about 100 types in-between. When you order Galvanized steel, it’s all mild steel, with only about 1-2% carbon, is easy to drill, cut and bend, but can take the heat of a fire (it’s not as pretty though as polished stainless !!! ).

I personally use stainless pop rivets though, instead of aluminum on the firewall. They hold up better to heat in the event of a fire (look for the high sheer strength type, like kitfox provides). You will have to special order them, to get the good stuff.

Hope this helps

Roger

[DanB]

Roger
The only reason I would stay away from galvanized sheet is due to the off-gasing that may occur in the event of a fire. Galvanized steel is coated with zinc...when zinc is heated, it gives off zinc oxide which will make you sick known as metal fume fever. Usually symptoms like the flu. Welders know special precautions need to be taken to weld the stuff.
FWIW

[rogerh12]

Dan;

Good point, I never heard that about burning zinc, but thats good info. I have some, maybe I will put a propane torch on it and simulate a fuel fire under the cowling, and not the effect (will it just melt away, or gass out).

Roger

[Av8r3400]

Please don't do that, Roger.

Burning the zinc off galvanized metal is not a smart thing to do. The off gassing of zinc oxide is very toxic and 'can' make you sick but can also land you in the hospital with a serious, life threatening case of blood poisoning from breathing the fumes.

(Speaking as a former engineer, welder and machinist. I called the ambulance.)

[rogerh12]

Thanks for the safety advice. Here is my plan (as I was wanted to use Galvanized steel on my kitfox, and am interested in the results):

I think my test will involve using fuel to burn against the galvanized metal, to simulate a fuel related engine fire. Placing fuel in a open tray and allowing the flame to touch the formed Galvanized steel, and also catch the melting zinc in a lower tray (if it does in fact melt away, and not just gas out). The results will be noted.
Fourth of July is coming up anyway, and a number of us (reloader guys) have a bit of extra fun around this time of the year :-) out on the farm , if you know what I mean. That would be a good time to play made scientist again. It is not necessary that I stand near the burn test; I have remote monitoring equipment, so breathing in fumes won't be a concern.
I will update the group on the results (oh, so I guess I better say, unless your experience with volatile chemicals and potentially explosive materials, don’t try this at home).
Roger

[szicree]

When I was in high school metal shop I decided to create a little metal sculpture of a surfer and wave from some material I found in the scrap bin. After I was done welding it I proudly showed it to my instructor expecting at least a "cool". What I got instead was "Do you know that's galvanized steel?". Like a smart-aleck teenager I said "Of course, I don't want it to rust." He then explained to me how you're not supposed to weld on galvanized metal and that I would likely get sick. I did. Spent the next day in the bathroom. I'm told it can be much worse.

Regarding a burn test, why bother? Zinc melts at about 800 F. and vaporizes at about twice that. An engine fire is gonna burn it right off and the fumes (especially from the aft side) are going up yer nose. Having said that, an awful lof of airplanes use galvanized firewall. To each his own, but is stainless that much more money?

[Dave S]

All the comments about zinc fumes being toxic are most certainly true - the classical way people poisoned themselves where I grew up was to take galvanized angle iron salvaged from numerous defunct windmills around the countryside and do the welding thing.:eek: A person can also fume zinc off by overheating a brass brazing rod (which is copper and Zinc alloy) Zinc oxide is used for a lot of things including medication, and as a food additive :)and (this next one should keep people away from it) an ointment for diaper rash:(.....Sort of the old deal that the difference between a poison and something good is only the amount - and inhalation is the easiest way for someone to overexpose themselves - doesn't take much.

Thinking about this a bit - not so sure a galvanized firewall would be the biggest threat in the event of a fire since there is plenty of resin in the fiberglass parts covering the engine which may get to a person before the zinc ever would - but I guess I favor the angle that cutting out as many potential risks as possible is a good thing - I like the SS firewall and SS rivets idea best.

Dave S
KF7 Trigear
Factory SS firewall

[rogerh12]

Hey guys;
We are not talking about wielding the metal here, but heat being applied more indirectly to the firewall, which will cause a gentler rise in temperature. I am not aware that zinc will undergo sublimation in this case, I think it will first melt and run off, but I don't know. That is what I will be testing. After the fire, will I have a bowl of zinc runoff, or nothing but zinc vapor? This should be a good determination. If I don’t' see zinc in the bowl, I won't be using this stuff anymore I my planes !!!!! (which so far has been on all my planes, as I recall).
Important stuff guys !!!!
p.s. There should be nothing under the cowling that can burn, if at all possible. Use metal and silicone lines, and when in doubt, try to burn the materials with a lighter, if it stops burning a couple of seconds after removing direct flames, it won’t sustain ignition by itself, and that’s a good thing.
Roger

[akflyer]

The zinc wont melt and run off, it will burn with a greenish tint to the flame then turn to a white ashy powder. I have cut and welded thousands of feet of this stuff for gratings, catwalks and various other structures.

If you have an inflight fire, the least of your worries is going to be a little bit of fumes off the firewall. What about the acrid eye burning wiring that is smoking up the cockpit, the fuel and oil and all the other goodies that are under the cowling. The fiberglass cowling really smells great when it starts to burn too.

If your that worried about a little bit a fumes on the firewall in the extremely rare chance that you have an inflight fire, then maybe you should take up something safer like being a couch potatoe and whatching TV while you knit a nice sweater... I am betting that the impact with mother earth is gonna mess you up a whole lot worse than sniffing a little zinc.

[jtpitkin06]

Even though engine fires are pretty rare, the firewall is not an area to cut costs.

I usually refrain from “There I was…” stories. But for fire or smoke in an airplane I will make an exception. Maybe it will help someone make prudent decisions on circuit design and fireproofing.

I had in in-flight cockpit electrical fire in an MD-82. We went on the O2 masks and smoke goggles within seconds of detecting fumes. Even so, the burning insulation immediately started my eyes watering and nose running. From 35,000 feet we did a high dive into STL and were on the ground in 8 minutes.

Burnt insulation is rude stuff. My throat was raw, eyes burned and bloodshot, snot filled my mask. Both the FO and I reported that for a week after the event, everything we ate, sniffed, or drank, smelled and tasted like burning insulation. It’s like skunk. Not the worst smell in the world, but it stays with you.

Now, I doubt there are many Kitfoxes flying with pressure purging O2 masks and smoke goggles. So your exposure to fumes is going to be a bit rough if you have a fire.

With the above in mind, why add the possibility of zinc fumes to the mix? Stainless steel 0.025 sheet is available from ACS in cut sizes. A piece large enough for a Kitfox firewall and foot wells is about $93. To that you will need to add the 0.035 fuselage cover under the rudder pedals. That will set you back about $25. Then you can have fun cutting it to size and doing all the bends. Or….

Order a firewall from Kitfox. I did just that and received a nice kit with pre-cut and bent footwells, rivets, fasteners and bottom cover plate. Life is good.


Build safe, fly safe
John Pitkin

[rogerh12]

Hey you guys are scaring me !

Shoot, maybe I should install one of those high dollar Halon system under the cowling or something !

My only really scary story was when my wood prop broke off my plane at 6000 AGL (I hear that is a rare event too, but still it did happen to me), but at least I had 6000 feet of cooling air on the engine, all the way down, down , down …

For me, I have to use the larger cowling to fit non-rotax engines, that means making my own firewall. I already have the galvanized stuff, so knowing what will happen to it in a fire is worth my time to test it (I kind of feel like a mythbuster too!).

[enyaw]

When you do your test, don't forget to add a container that will contain and focus the flame on the firewall (simulate a cowling) with a 60-120 mph wind entering from the other end.....

[Lion8]

Many good tips here and all are right on. I welded for a Power company, in a Nuclear Power plant. During the construction phase, I was given $.35 an hour over the rate to weld Galvanize. Yea, right. I so much as told them to put the $.35 where the sun don't shine.
As far as the material, I made a cardboard firewall, this gets transferred to
aluminum coil stock. This is the material used for window and door trim on siding jobs. It is about .018. When I'm satisfied, I will transfer or use this as a template to the S/S.(Aircraft Spruce). You can not use a portable aluminum brake for S/S. I have a tech advisor who has a 4ft. heavy brake I'm going to use for the final produce. -Tom, N.J.

[rogerh12]

Oh how I long for those simpler days !!!!
Simple ice cream choice (chocolate or vanilla)
Simple summer drinks, Coke or Pepsi
Simple firewalls, Galvanized or Galvanized.

Roger

[mr bill]

Cessna and Piper used galvanized on the 150s. They are hard to keep clean and after some years, they rusted and looked terrible. The later 172s, 182s etc used stainless. Those are much nicer in appearance.

[Dave F]

Stainless is the only way to go.

In Canada for homebuilt category you only allowed to use SS
No galv or Alum allowed.

looks better as well

[HansLab]

I choose to use a FW-blanket (out of this forum, as well) http://www.heatblok.com/product.html
Hardly costs anything, great performance.

[Dave F]

Zinc melts around 800F that is dull red colour............. and getting hotter. Sure you might not get the submlimation but you all that take pride will save what -- 75$ and get a galv metal that will look like crap in a few years.

To each their own...... and it is just as workable unless you use dollar store Brake, drills, etc.

[Eric]

I hve made a new one from 0.4 mm High gloss SS and that looks great
My original one was made of aluminum and the plane has been certified in the US with that material?
My plane is a 1991 KF 3
Maybe skystar delivered that kit with an aluminum Firewall.

[Lion8]

Just another point on this issue. I have stainless steel that I will be fabricating my fire wall with. Yes, the S/S will hold back flames better than Alum, and Galv. does put out some nauseous gas, however, if there is a fire, the fiberglass, rubber, plastics, fabric, adhesives etc. will produce some noxious fumes as well. Just something to think about.

[Esser]

My $.02. When you are trying to get on the ground as fast as possible because you have a fire nothing else will matter and you will wish you had the best material to give you that extra time. Fire in the air is probably the only thing in flying that the idea of actually scares me and it only takes minutes. Go to the AOPA website and listen to some of the crash stories that involve mid air fire.

[jtpitkin06]

You can make a firewall from lots of different materials. It’s just a matter of how much time your material will hold back the flames. Wood and fiberglass seem like poor choices, but that’s just a hunch. Gypsum board might be a bit heavy. Blankets on the engine side of the firewall make great wicks to hold leaking oil and fuel.


Aluminum melts at 1200F and steel at about 2400F. Gasoline being fanned with air burns about 1400. Hmmm. This might require some deep thought.


Inre: SS vs. galv. Several aircraft manufacturers used galv. Heat and fumes take their toll on the galv.. A mechanic showed me a Baron that has a galv firewall covered with rust. Firewall foreward will have to be pulled to get access and remove the corrosion. Yeowch! That makes SS an easy choice.


SS looks pretty.


John

[dholly]

To add another thought...

Following info is from a 3/95 Experimenter Magazine article titled Firewalls By Tony Bingelis
Acceptable Firewall Materials

The following materials may be used in firewalls WITHOUT BEING TESTED;

- Stainless steel sheet - .015 inch thick (.284 lb./cu. in.)
- Mild steel sheet (coated with aluminum or otherwise corrosion protected) - .018 inch thick
- Terne plate - .018 inch thick
- Steel or copper base alloy fittings
- Other materials may be used if they can pass the fireproof test.
I know ACS sells Galvanized Sheet, 26 Ga., .022", 2.718lb per 12"x48" and 304 Stainless Sheet, ?? Ga., .018", 2.173lb per 12"x48"

Since you typically have to use a heavier gauge of galv. vs stainless to get equal fire resistance, I considered using a thinner gauge galv. with fire stop paint (see: http://www.aircraftextras.com/Contego.htm) on the engine side and a fire/sound blanket on the cabin side.

This might provide equal fire protection without the noxious burning galv. gas concerns, at the equivalent or lesser weight with the benefit of a reduced price overall. Personally, I'm not building a show plane and galv. is a whole easier to work with the tools in my garage. Perhaps more importantly, I can source the galv. sheet locally but not the stainless.

Any comments on that approach?

[rogerh12]

I had a galvanized steel firewall on my Zenith 601 HDS. After 15 years of service, it had no corrosion to speak of, but was not a thing of beauty (though it got the job done). It was easy to drill through and in general, easy to work with (stainless, not so easy) I patched a largish hole with a sheet during an engine change, using some some stainless rivets ( which didn’t take long). But that carbon steel patch look pretty rusted two years later, though the firewall itself still looked the same (looked good enough).

[jtpitkin06]

Stainless Steel.
Doing a little extra work back when I obviously had WAY to much time on my hands.

JP

[rogerh12]

If at all possible, don’t have anything under the cowling that will burn, at least not burn well. Silicon hoses and such are a good choice, and use fire jackets on the fuel lines. Also, if you do have an in flight fire under the cowling TURN OFF THE FUEL BUT KEEP THE ENGINE RUNING. The fire will probably go out by itself once the engine uses up the remaining fuel in the lines,filter and gassolator.
Hope this helps
Roger

[Dorsal]

John, Sure looks pretty and I really like the way you did the edge.

[GWright6970]

This is a VERY good thread. Many of the items discussed here are in an NTSB accident report for my local area.

Two items discussed locally (by those of us who knew the deceased owner) of the aircraft described below in this NTSB File, (and were finally able to talk about it in our hangers months later): 1) It seems that someone used aluminum rivets in this firewall, which melted and well, allowed the flames to melt the rivets and drop the attached plates and allowed the flames reach the pilot/owner in the front seat. 2) The fuel line fitting described as "industrial" is believed by most of the builders here at our airport to be for a vehicle, which I understand has a different "pitch" or "angle" than aviation fittings, causing a mis-match in seating surfaces. I must say that while Vern was not the registered builder, he was known to do extensive work and repairs on his aircraft. How it got this way is probably not known.

VERN DALLMAN was an excellent guy. Every year he hosted an annual safety day for aerobatic pilots at his ranch.... I could go on, but suffice it to say, that we still remember him, and miss him. Dang sad.
Grover
************************************NTSB FILE: #LAX99LA063On December 31, 1998, at 1151 hours Pacific standard time, an experimental Young Harmon Rocket II, N288M, was destroyed following an in-flight fire and hard landing at a private airstrip near Esparto, California. The commercial pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. He and one passenger departed approximately 10 minutes before the mishap. The pilot was in serious condition after suffering burns over 1/3 of his body and succumbed to his injuries over a month after the accident; the passenger sustained minor injuries. Visual meteorological conditions prevailed for the local personal flight and no flight plan had been filed.

The pilot completed one flight and was taking another passenger up for a short flight around the area. On the downwind leg witnesses reported everything looked and sounded normal, and then they heard several pops, which they attributed to the engine being throttled back. One witness asked the other if the airplane was on fire. The flames he thought he observed went away. They dismissed his observation as sun glare and turned away. When they looked at the airplane again on base leg, 2 to 3 feet of bright yellow/orange flame and a trace of black smoke emanated from the cowling. On touchdown the airplane bounced, hit again, then skewed 20 degrees to the left. The left main landing gear collapsed outboard and the right main collapsed underneath the airplane. They gathered fire extinguishers and did not see the airplane come to a stop.

The passenger stated he saw light gray smoke in the cockpit and notified the pilot. The pilot secured the master switch and turned onto the base leg. At this point the passenger did not observe flames or feel any heat. As the airplane turned wings level onto final, thick black smoke that smelled like burning fiberglass or plastic filled the cockpit. After the airplane came to rest, he observed flames around the pilot and felt high heat. He yelled to the pilot to open the canopy, but the pilot responded he could not get it to open. Momentarily, the canopy opened halfway.

As the rescuers arrived, flames were still coming from under the cowling. The front cockpit was so filled with smoke that they could not see if the pilot was still in the airplane. The rescuers helped the rear passenger out, and then noticed the pilot on the side of the runway.

A Safety Board investigator and a representative from the engine manufacturer, Textron Lycoming, inspected the wreckage in the owner's hangar on January 13, 1999. The engine was a Textron Lycoming IO-540-C4B5, serial number RL-6849-48.

The engine exhibited thermal damage in the left rear section. The fuel flow divider on top of the engine was sooty, but undamaged. The fuel injection unit on the bottom of the engine was undamaged. Components in the front right quadrant were not discolored or damaged. Discoloration and damage became evident and increased in severity moving toward the components in the left rear quadrant. The engine controls appeared secure at their respective mountings.

Components of the accessory section at the rear of the engine displayed damage. The engine driven fuel pump displayed more damage than the other accessories. The airframe in this area exhibited the most damage.

The aluminum housing of the engine driven fuel pump had melted and the center section of the pump was disintegrated. Fire consumed the pumping chamber, valves, and diaphragms. The top half of the pump remained securely attached to the engine. The bottom of the pump fell into the rubble. Molten metal remained on the lower portion of the pump piece that remained attached to the engine.

The attachment fittings for the inlet and output fuel lines for the fuel pump were detached and lying in the engine compartment. The inlet line had globules of molten metal on the threads and around the fitting. The output fitting did not have any residue on it; the threads and fitting were clean and undamaged. The fire sleeve surrounding the output line changed colors moving away from the fitting. Several inches of fire sleeve nearest the fitting were gray on the engine side and black on the part of the line that rested against the black engine mount. The fire sleeve then became orange, the same color as undamaged fire sleeve. The "B" nut on the output fitting was 1 1/4 turns loose. The remaining fuel line "B" nuts were secure. The Lycoming representative described the fitting as an industrial fitting rather than an aviation fitting, but he did not observe any evidence of mechanical failure.

Investigators removed the fire sleeve from the flexible fuel lines. They did not observe any damage or chaffing of the braided material. They did not find evidence of any ruptures or other hose failures.

A condition inspection (annual equivalent for amateur-built experimental aircraft) was completed on November 9, 1998, 10 hours prior to the accident.

The Safety Board investigator released the airframe wreckage to the owner's representative on January 13, 1999. Components retained for further study were returned to the owner's representative on March 23, 2001.

[jtpitkin06]

I’m posting the following on this thread as I think it pertains to firewall protection information. The firewall keeps out flames and it should also block fumes from entering the cockpit.

Dorsal mentioned the edge on my firewall. It is the mounting flange for my cowling.

My cowling is a Continental unit from Kitfox. It came as a two piece assembly. The top going all the way back to the windshield and the bottom going all the way back to the door frame.

In order to keep fumes out of the cockpit I wanted to seal the fuselage from the firewall aft to the door frame. This would not be possible if the cowling remained in two pieces. Every time the cowling is removed it will require resealing.

The solution was to cut the cowling into several pieces and fabricate a boot, a forward lower and a forward upper cowl. The boot gets sealed around the windshield, door frame and firewall with weather strip. It will be only removed for major maintenance. This ensures fumes and water stay out of the cockpit. Removing the forward upper and lower cowl for routine maintenance or service will not disturb the weather strip.

The boot is attached with 10-32 screws around the perimeter for a tight seal. The cowling is attached with Cam-Locs for easy on and off inspections.The firewall flange is riveted with brackets and Hysol along the entire joint seals the inside junction out of view.


I think of the firewall and cowling as a system. It provides engine cooling, cabin heating, fire protection and noxious fumes protection.

John Pitkin

The photo shows how a piece from the lower cowl was joined to the top aft section to form a one piece boot.