Can't wait for the Darkaero Marshmallow Man to make it into the FARs! Great work guys. I'm really enjoying watching good engineering practices in motion.
The best extremely lightweight firewall material I've found to stop radiant heat is generally known as griddle brick material. I've used it in numerous composite builds since 1991. Grill Bricks are a pumice-like cleaning block made from recycled materials. Basalt is the primary ingredient. The conveyor furnaces that shape the raw ingredients is way north of 2,000 F. This material is also used in chemical plants to insulate high heat pipes. I have a source in the DFW area that purchases the 4' X 4' X 8" blocks then cuts it into half round radiuses to insulate pipes. The material is very brittle but has a very high impact absorption strength. It smells like Sulphur when cutting it or picking at it but the odor is safe for animals and humans. Incapsulated after cutting there is no smell. It's one of my proprietary composite blend secrets that I'm now releasing to the public. It will dull normal cutting tools in seconds. Cheers
We used fire brick and insulating block for radiant head stoppage in fuel fired boilers, it’s made out of the same material and we had firebox temps up to 2500f, out side temps were around 95f. That’s steady state running for hours. Great point you have!
@@_Joy_Unleashed - Most public releases to what was once considered intellectual property or proprietary are now freely available as a public release on RU-vid. I like open-source information. It's a shame many also post click bait and untrustworthy information as well. My intention is to offer what works especially when it comes to aviation projects and the great guys with DarkAero. I love spending time with their valuable channel. The plus side is reading the comments of their channel. A great community of folks in my opinion. Have a blessed day!
Dont forget the smoke coming from resin in the final carbon structure. We use a special UL94 resin for carbon firewalls with honeycomb on a racecar and they are a pain to work with. They need a specific tempering heat cycle after curing otherwise they become very brittle.
I just found this project and am loving it! One thing I recommend though: have an "overview" video pinned to your RU-vid page. I don't think you even have a complete overview video of the project at all. Something that includes: goals, aircraft specs, mission, deadlines, etc. It could be almost like a commercial if you wanted to go the route. I watched about a dozen videos before I finally realized I have to go to your site to find specs.
Pay attention to materials based on magnesium oxide. MgO boards with fiberglass have a very high fire resistance. Also on the US market there is a material called "Airkrete foam" based on MgO. It is a very lightweight refractory material used in construction as insulation. This material can be used in aviation because it is very lightweight.
After watching Scott Manley’s videos about Apollo issues I am more than supportive of proper parts testing. All the duration, all the parts, zero assumption.
How do you ensure the heat does not break the structure of the airplane apart? I mean, what good does the firewall do if the front falls off and the weight of the engine is gone.
Ryley, this is the best video I've ever seen on firewalls. I'm converting a single-place motorglider Silhouette to be all-electric. Each battery compartment needs to be a small vented fire-resistant environmentally controlled compartment. This was excellent reference material. Thanks!
This is exactly how cirrus aircraft firewall is built. Yes, it works....mostly. I've repaired one that caught fire. It stopped alot but not all. I was able to save the plane by replacing a large portion of the structural firewall then the entire fireproof metal and ceramic. It did save the pilot from harm
Great presentation. And now I know I can wear my marsh mellow sneakers flying the DA1. They are sooo comfortable. The kids say, “they look so totally fresh!”
Really interesting. It’s amazing that just 1/16th of stainless or titanium held back a 2,000f blow force for so long! Have you considered selling little bits of the honeycomb structure to help fund the project? Or would it not be economical? They just look so cool!
Another great vid! I'm very surprised FAA says nothing about radiant heat. Anyways - marshmallow test rocks. Question..after you finish Dark Aero 1, will you be developing a 2nd plane type optimized for other missions?
Thanks for watching Eric! We are pretty focused on the DarkAero 1 for now but we’ve definitely kicked around the idea for a DarkAero 2. Seems like it would be a logical progression if we are successful with the first design. :) One airplane at a time though!
It would be interesting to know whether the firewall provides any structural strength to the aircraft's frame/body, and if so, what impacts the high temperatures have on it's structural integrity.
I wonder about flames that aren't centered on the firewall. Imagine, for instance, that an oil line busts and sprays hot oil that then catches fire near the edge of the firewall. What happens to the interface between the carbon fiber airplane structure and the firewall? Also, how does a fire affect the structure of your front landing gear? IIRC, that's mostly aluminum and mostly forward of the firewall. Does the slot for the landing gear pose any kind of threat for ducting fire around the firewall? If the gear in the engine bay were to melt or warp during a fire, you'd presumably drop the nose onto the runway during the landing. Do you have any sense of whether the plane would tend to flip if this were to happen? You guys are a huge inspiration. Thank you.
My guess would be porous silicon rated to 2,300 degrees F or a 'Starlite' like material that forms carbon foam. Polishing the titanium layer can also assist against passing radiant heat to the cabin.
My guess on the new secret material for the firewall is "reinforced carbon/carbon matrix". This is the material that was used on the space shuttle nose cone and leading edges of the wings. This material withstood the temps and shielded/protected the titanium super structure of the shuttle during reentry into earth's atmosphere. You guys have incredible carbon matrix composite skills already so this could be a reasonable next step for you.
Enjoying your content guys and watching your progress. About the Firewall. Perhaps you know already, but aluminium is the best material to accept ceramic coating.... that’s why they use it to coat pistons in very high performance racing engines. Perhaps you could have your first sheet in the firewall laminate structure ceramic coated?
I'm sure you guys have already settled on the design you are going to use for the firewall, but I'm curious. Did you think about infusing the honeycomb structure with starlite instead of the ceramic blanket, and if so, what would be the reasons to not use it? 😁
AWESOME...........Just cool as heck....... Any chance you guys ever build the RC Version (1:3 or smaller) scale? Just to see what the smaller version would fly like? I know you performed fluid dynamics modeling to verify much if not all of your flight characteristics but was just curious? Anyway Thanks for all your sharing and looking forward to 2022.
What could be more "cosy" than curling up behind a glowing light aircraft firewall with a glass of red and a loved one, or a DarkAero marshmallow man? 😉
I have a little secret about stainless steel. It does not radiate energy very well. You notice all those cool drinking mugs made from stainless? It's not just the vacuum that insulates. The high nickle chromium content refracts the energy back into itself. So yes it glows, but the transmitted energy is much less than carbon steel or titanium. I personally saw an old time wood stove with a brand new 16ga 304 stainless shell. You literally could not burn enough wood to heat a room. The top cast iron part was the only thing transmitting heat. The same stove before with carbon steel sides would run you out of the whole house in an hour. In my opinion this explains the less toasty marshmallow man on the stainless test. Really awesome test setup by the way.
If cost is not an issue the use of titanium is a very reasonable choice. As shown by other manufacturers some materials may just not be "necessary" to achieve the desired result cost effectively? Just the opinion of a former AF Crew Chief, if the engine fire was serious there would be melted blobs of engine aluminum flying around long before a firewall would fail. Cool vid to watch though and it's interesting to see the hoops you guys are jumping through to get FAA certified.
Hi, The honeycomb structure has many pockets of air, which can act as a micro pressure chamber on each air pocket when there is sudden increase in temperature and how do you solve these problems. Because you don't want to lose structural integrity of the firewall in that situation. Which leads to set of new problems.
Are you asking about just waste heat from the engine running? or heat from an engine fire? Either way, the canopy is made from thermoformed acrylic which will soften when it gets hot enough but it doesn't turn opaque. Thanks for watching! :)
@@DarkAeroInc Thank you for the answer😉 I was asking especially for engine fire sitation Amazing work! I hope to see you in flight as soon as possible😉😉
With your testing its all well and good doing in house make shift testing but do you have to qualify your builds to proper standards like RTCA DO-160. Specifically section 26 talks about fire and flammability. I know a lot of COTS products will already have this but stuff you guys manufacture in house?
You could try an emissive refractory coating to reflect some of the heat. ITC 100 or ITC 213 Ceramic Coating for example. You'll have to ask them if it keeps sticking over the years though...
I think that might be too fragile for continued use in flight. I would also suspect that the vibration and shifting of a failing engine in flight could knock away the carbon foam created pretty easily. It is a good idea, though, and I would like to see it tested. Maybe there is a spay version that could go over the finished firewall as extra layer of protection to give more time to the pilot.
@@David-yy6hp Good point regarding vibration effects - a practical and valid point that is NOT addressed in the FARs (at least not as covered in the video). Addition of starlite would still be an interesting test, even if some method to simulate engine vibration were added. I wonder if the light weight of the carbon foam might protect it from flaking due to mechanical vibration. Simply coating in 'starlight'-like material might also be prone to inadvertent mechanical damage in service (which would result in compromised protection), but it could be protected with a tough sacrificial coating.
@@robbmain1684 I saw a video by nighthawkinlight about making the coating stronger through the addition of borax, which created a glass-like binder for the carbon foam. A carbon/glass foam manufactured more cleanly might be a very good approach, but then it starts to mimic ceramics. I think that a carbon foam layer, if it could be made to withstand vibration, on the engine side of the firewall could be useful for heat dissipation due to the radiative properties and the air entrained inside of it. I would love to see some tests on carbon foam materials and their implementation cost as well.
Okay, I'm going to ask a dumb question: Would a halon fire suppression system for the firewall forward area makes sense? Oh, and add a fire sensor too.
Yes. Race Cars use those systems and they are mandatory in any professional racing. They weigh about 7-10lbs for a small one. The only issue in an Airplane is the huge volume of air going thru the engine compartment will blow the Halon out the cowling immediately. Whereas a race-car usually crashes and stops before the extinguisher is utilized. An airplane can actually put the fire out by diving to VNE or Vd in some cases, and if that doesn't work to blow out the fire like a candle, at least you're diving toward the ground as fast as possible and will therefore land as quickly as possible. In an aircraft, an IR sensor for heat or a wire that melts and illuminates a warning light in the cockpit could be beneficial.
I think you should think about adding Teknofibra to the firewall. It’s excellent for fireproofing as well as soundproofing. Maybe that’s the mystery material you’re talking about
Merchandising, merchandising, where the real money from the aircraft is made! DarkAero-the T-shirt, DarkAero-the Coloring Book, DarkAero-the Lunchbox, and last but not least DarkAero Marshmallow Man the Plush Doll!
Wouldn't an air gap be a better than having solid insulation? From my exhaust experience we typically use a stainless and insulator sand which and then an air gap between the surface to be protected. Doing the math, thin layers with air gaps are the best defense against radiated heat.
How do you calculate cold temperatures and low pressure at high altitude. I assume every carbon fiber part would need to bleed pressure including the honeycomb cores.
I'm curious about carbon fiber as an insulator. In my test a few weeks back I pointed a MAP torch ( ~3700F ) directly at a 1.5mm thick sample. The binder obviously burned immediately. After about 2 minutes though the binder was gone and the face of the carbon fiber sheet was bright red, but the rear didn't show any color change. Any chance this is part the setup you're testing out?
instead of the ceramic layer why not an Intumescent layer between the titanium and the CF sandwich? As it heats up it expands and provides greater level of safety. perhaps to the point where the cf sandwich would be undamaged.
What temperature does the resin you use catch fire? A cirrus here in Colorado caught fire in flight and the fire went thru that plane real quick. Needless to say nobody survived.
I hope you see this but i realize its an older video...but why not use inconel? Im not fimiler with airplane specs but i have a motorsports background and anything high heat high melting point low thermal transfer ect inconel was the go to...not on the list??
I have a feeling the firewall youre trying out is Starlite and since its made from PVA glue mixed with corn starch and baking soda would be very cost effective. The fact you can coat your hand in it and then take an Oxy Acetylene torch to it is proof enough its the best firewall except for being ablative so it wears aways over time.
I am very interested to see a real test of a through-firewall connector or a cable guide or a fuel line... These are the real weak spots, in my opinion. Have you tested some foaming paint systems, like FlameRest?
I guess you will test kevlar, Aerogel and/or Starlite(by NightHawkInLight version ) or a combination of the three🤔 Just search for intumescence for Starlite like Materials
Insted of just a solid layer of Ceramic insulation use grinded or flakes of it, it will fill it with more air hence more heat dissipation and lower temperature of marshmallow man✌️
Tungsten skin (foil), asbestos insulation blanket, then a Aramid fiber interior skin(Kevlar/Nomex). That combo would stop anything. I doubt any heat would transfer through it.
Example scenario, you are landing and a weel fails because of a puncture. Plane gets hard to control and impacts the front with a slight angle and hot engine... fuel pump still running? Arms broken from the impact? How do you get out? Are you still protected from the fire?
Maybe covered in a different FAR, and maybe already planned for an upcoming video, but will you cover how you plan on protecting firewall penetrations? I assume harnessing will go through bulkhead connectors (are they specially rated?), what about things like the fuel line, mechanical linkages, etc.? It's all very well to have a brick-s**t-house firewall, but if you fail to protect the holes that you require in it, it can still go up in smoke! Also, you comment on fumes from the carbon fiber (or more likely, from the resin) - are there no requirements to deal with outgassing under these conditions? Or is the plan to just open a window...? :-)
I'll answer about connectors: you can use firewall qualified connectors. There are various specifications, military in origin, two of which are MIL-DTL-26482 and MIL-DTL-38999, but there are more (I just happen to be more familiar with those two). Usually for most aluminum made structures in non-fire designated zones connectors made of aluminum and cadmium plated were favored, not so much in newer designs due to cadmium being banned for health and environmental reasons. For firewalls you have two options: passivated stainless steel ("K" finish designation) or nickel plated stainless steel ("S" designation). FAR are not always so detailed, and with every revision they become even broader. I suppose this comes from many complaints by the industry regarding normatives being so stringent that evolution is slowed down. Broader definitions and requirements allow manufacturers to use their know how and to incorporate more promptly newer non-standard solutions, as long as they comply with key requirements. Nevertheless, FAA mantains a series of Advisory Circulars, which are nonmandatory guides giving details on how you can comply with FAR, and there they do specify hardware, materials, procedures, etc. as a reference based in previous proven designs. On the fumes issue, I cannot recall now but there's quite possible a paragraph addressing that, it was one of the reasons for PVC being forbidden as wire jacket material in aircraft. In any case, if it's not mentioned in regulations but the FAA still considers that there's reasonable risk, they will ask you to solve it.
Can the Ceramic Heat Shield Blanket, at 1/8", be Doubled in thickness? Compare Marshmallow Man, against Nut Man, and a Woods Metal man! (Sprinkler Plugs!) I would suggest, the Temperature, 1" to 2" from the Firewall on the Ties side, should not exceed 110°F, but Ideally, be kept under 85°F, in a Full on, Forced Air, In Flight Engine Bay Fire!
