Said it before and I'll say it again: I'm not a pilot and will never be able to afford my own aircraft, but damn I love seeing the engineering approach in these videos. Wishing DarkAero every success.

These videos are too good to be only 13 minutes long and a month apart.

I appreciate the CAD walk through. It makes daunting and complex looking system design seem much more approachable when you can break down how the final result was achieved.

You guys are incredible. It is so fine to see an aircraft being designed by professionals instead of enthusiasts. I hope this aircraft is an absolute success for you brothers. Well done.

22 seconds in and I’m upvoting because of the amazing humility and focus on quality, safer, and innovation you have explicated in that short amount of time. And because, as a self-taught journalist with a decade’s experience as the tech editor of a CAD industry trade magazine, I must highlight that you got the most important bits above the fold.

Awesome as ever! Nice to finally see a video where the creator accept they got something not quite right and then showed how they fixed it. All too rare in the KZfaq world. Well done guys and keep it up, this is awesome stuff! 💪🏻

I've always felt that sumps were easier to design if they were narrow and tall, not wide and low. But it looks like you made it work.

I'd think you'd want the fuel return lines going to each wing tank and not the sump to keep the entire system properly pressurized and not get back-pressure on the feed check valves causing vapor lock. *You also want to install an air return line into the highest point of the sump to the highest point of the wing tanks should air be introduced into it during maneuvers. The sump could use a baffle across the center with a hole for crossing. But I think the shape you created for better contamination tests accomplishes this fine. I'd do the math to see how long the fuel in the sump alone would last under climb and cruise power to see if the sump is large enough to carry you should you encounter any feed issues. Wouldn't hurt to double the feed lines to the sump in that regard. I forget the wing tank layout and whether you baffled the pre sump feed area but that would be a good idea to prevent air entering the sump area. *I think because the sump is not large (I know you all are working with constraints) the fuel will start moving rather quickly there and air could be introduced if not properly accounted for. It also needs somewhere to go if it does.* Now to discuss my consultation fee...

I am so impressed by you guys !

Another reason wings are good for fuel storage is because the wing itself supports (and distributes) the weight of the fuel, and you don't need additional structure in the airframe to support the weight of a fuselage tank. Smaller, lighter spar, smaller lighter spar support structure.

Every video y’all put out is fascinating within itself. I’m so excited for your whole team. This isn’t just another neat airplane being built. The tech and foresight your team is using will advance the aviation industry by leaps, not steps.

Love every single update you guys out out. Your engineering and attention to detail is spot on, as it should be considering you're building a machine that's going to fly through the air at over 150 kts. Can't wait to see this thing take to the air!

The best part is no part. Great job simplifying this tank.

It's wonderful to see the engineering design cycle so beautifully demonstrated here by a group of serious professionals. Just awesome!

Great work guys! Have you considered fuel heating when recirculating back into a tiny volume at high flow rate? Might be better to recirculate into the high volume main tank which is "aircooled". I see that you are trying to solve the fuel selector problem as a source of potential pilot error and nuisance. Would it not be simpler and more controllable to replace a clasic fuel selector valve with 2 solenoid shut off valves (with manual override) that are automatically controlled by digital fuel level sensing? It would also solve the following threats: 1)One tank becoming unusable fuel due to a stuck check valve. 2)The higher tank feeding alone (side slip) causing an imbalance that makes the low wing even heavier and the high wing lighter. 3)Inability to isolate one tank if deemed necessary. With computer controlled balancing you could run different regimes 1) automatic balancing based on measured quantity (you could even program a deliberate imbalance e.g Keeping 30pound more in the right tank to minimise control deflection with single pilot ops). 2) Automatic switching after elapsed time (if fuel aensing fails) 3) both at once 4) manual operation as back up. Sorry, I can't shut up. Keep doing, what you're doing, you're doing great.

Can't wait to see it fly!!

Thanks for the walkthrough. All of you have a talent to explain very complex "stuff" in a very clear and layman way.

i really appreciate the little cad tutorial, gives an idea of how professionals approach cad

Another master class in aeronautical engineering, design & fabrication! Your team is well placed to teach engineering design at colleges & universities.

Been sharing some of your videos with my local engineering team members! Thanks for sharing about how DarkAero follows Engineering process and some of your innovation! Love the video format and communication, so easy to follow and fun to understand.

I just Love how focused you guys are on everything you touch. Look forward to more videos. Thank You!!!

Excellent! I see two considerations not mentioned in the video: Static electricity (Electrical bonding of components and structures) and provisions for thermal expansion of fuel and potential leakage at overboard vent ports. A lightning strike would be worst-case, but static can occur in places you may not expect to find a difference in charges. If using high octane fuel this is especially important.

Wait….DarkAero posted and I missed it? I need to up my game!

I know it's not part of the scope of this design, but one thing I hope becomes a thing in small aircraft design is a battery backup system for aircraft engines that can drive the prop for a minute or so, such that pilots have time to land in case of engine failure. You guys' commitment to safety is extremely effective wrt the resources available to you, though. The redesign of the sump tank is brilliant.

You guys are awesome. Love watching this coming together.

Nice design improvement. You're generously transparent about the design process. Do you have additional drain ports in the wing tanks? The reason I ask, is because if any part of either wing tank sits lower than the wing-tank outlets, then it might be possible for water/contaminants to collect in areas that aren't drainable while parked.

You guys are 50% aircraft designers, 50% aerospace educators!

Brilliant redesign!

Quality work gentlemen! It would be interesting to see tesla valves integrated into your wing and sump tank to reduce slosh and wing to wing transfer. Keep up the good work team!

Would love to kow how do you collaborate with your test pilot. How does their input and prespective shape aircraft development, design and building in your case. Great video as always 👍

With such brilliant engineers and innovators like you guys ... watching this evolution is not just a pleasure but a blessing. People don't understand iterative development ... and how EARLIER thought contibutes to future mods. I mean the videos you put out ...are ... i don't have words ... ♥♥♥♥ It is INDEED a Dark Arrow in the world of innovative airplane design ... you don't see it ... but it's there and coming in strong!

You guys are impressive. I only wish I was 40 years younger… I’d have a deposit with you already. 🇨🇦

Soooooo glad you guys are taking the time to design “good testing rigs” and redesign the potential problems way before a customer encounters them. Textron doesn’t even put this much thought into their products, they just wait for customers to hit the ground then say oh, I guess we need to put more effort into that dumb flawed idea.

This is a great example of the engineering design iteration process. Think about it, convince yourself that it is amazing, build it, test it, realize that it is not really amazing.....reapeat until the result is amazing.

Lotsa good thinking in here. Impressive.

I always assumed you’d have a foam filled surge tank in the system (between engine and sump) just in case of high-g or tilt impacted fuel rate.

I love your videos! I am a sport pilot working on my PPL I own a REMOS G3 all composite Light Sport aircraft. I love seeing your iterations and adjustments while it must be frustrating for you it shows your drive to get it right. I actually reached out to Aeropro to potentially buy their molds and specs for their project "Vison" ..... 6 Mill Euros lol meeting with a couple investor groups before I go out and look.

I am egregiously pleased with myself for having identified the salient problem in your excellent introduction to the design of the first sump and the conditions expected of its placement. Then, I imagined how I would have “fixed“ it, and I was essentially correct! _Hooray for me, I´m an aviation engineer!_

Should't you combine tilt with an analogous centrifugal force (spinning) when testing?

I am absolutely taking notes for my next plane build in Kerbal Space Program.

Can't help but wonder with all those great videos, when do you make a dedicated one comparing *V-tail, T-Tail* and what you ended up using?

What kind of epoxy do you use for the tank, or are you going to coat the inside with a coating that is compatible with the fuel?

What sealer did you use to prevent ethanol from eating the epoxy? The UL520is burns mogas and avgas.

Not having a fuel selector is a mistake. You want a way to turn off fuel to a specific tank in an emergency. It is barely any pilot workload you are adding, let the G3X manage alerts.

Do you realize how much money you could make turning several of these 15 minute videos and curating them into a playlist or curriculum for flight schools, Air Force training guides, engineering and physics courses and just all sorts of other schools, colleges, universities and other educational platforms all over the world! Literally 10x what you’ll make selling the plane. Edit: I started writing this before the 10min mark where he mentions they do have an internal course. But my point still stands it’s just even easier because there’s already a product in the one course.

Always informative and well executed videos. Will it work in inverted flight?

Great video as always. Can't wait for the next one.

Really looking forward to first flight

Is there any reason why flexible bladders aren't used for containing the fuel? Would a bladder not improve safety in the event of an accident?

My plane’s two fuel tanks have… Screens at the fuel pick-ups in the tanks… Sumps lower than the fuel pick-ups… Small dead space in the lower corner of each tank, because limitations in aluminum construction… Another screen at the bottom of the fuel separator below where the two fuel tank lines feed the separator… Tiny screens in front of each fuel injector… Each fuel pick-up is at the back of the tank… so it is sure to pick up fuel when the nose is high on departure… The pick-ups are at the inboard end of the tank… so it is sure to pick up fuel from the uphill wing during a slip to final… Fuel cap seals have been updated to be blue fluoropolymer seals to keep them from absorbing 100LL and changing shape over time… Tank vents are at the top corner of the up hill end of the tank, with a hose venting to the bottom wing surface… have a method to pre-flight for bugs… Things to consider when designing new fuel tanks…. 😃 (from a Mooney driver)

Keep going Riley, very happy reservation holder !

Great video, thanks! Question: You switched from carbon to fibreglass for good reasons. You are aware that fibreglass tanks need special sealant to avoid contact between the fuel and the epoxy? Especially when your users will put in Mogas with ethanol.. Would you consider doing the design in all-Aluminium?

i looked for your booth at Oshkosh but didnt find you guys.

Quick question: at 8:45 how can the part be removed so easily from a positive mould? Surely it won't work without some extra steps.

Great informative video. Did you already explain your design around the Vent Shuttle Valve somewhere? Would be interesting to understand that details of that. I favour you decision to do away with manual tank selection, but I'd also like to understand how the tanks will ballance statically and dynamically (During fueling, on the ground and in the air).

How do you deal with high roll speeds pulling fuel away from the sump? Similar with low G/ inverted maneuvers? I can see how the check valves in the sump have a good chance of keeping enough fuel in it during high speed rolls from starving the engine though. (Correct me if I'm wrong in thinking you need this as my understanding is this is a high performance/show aircraft or if the aircraft is not being designed with these maneuvers in mind) These videos are very interesting and have helped respark my love for engineering. I cant wait to see this project finished

Thanks!

opened KZfaq at the right minute!

That's cool) In my mind, it need some ribs between fastners.

I’m not sure I understand the purpose of having the sump tank. On my rv7 I just have the 2 wing tanks go into a single line and the a transfer line going side to side for fuel transfer. There is a selector switch like mentioned in the video but I always leave it on both. The diamond da40 work’s interesting as well where fuel is only pulled from the right wing and then the pilot has to turn on a transfer pump to pump fuel from the left wing over to the right wing.. this sump tank also appears it would create air in the fuel lines if flown inverted. Love the project!

How was the canopy made, could you provide some insights if possible

Fun fact, aero engineering is the origin of "one of," as in the engineer draws something and sends it to the shop with instruction to make one *of* these to see if it'll fit. It's mildly obsolete given CAD but it has a certain charm.

How wil MOSAIC rules potentially change Dark Aero in the long run?

even if you are not interested in engineering you will still be fascinated, kudos guys, keep up the good vibes. I'll keep dreaming 😊, ✌🏽❤️🇰🇪

Are there concerns about the fuel cell degrading from fuel contact w/ the composite matrix?

If/when the energy density of batteries approaches that of liquid fuel, would all of this fuel management engineering become obsolete? Do you secretly pine for the day this happens? Or is that a pipe dream?

It's always good when bug-fixing lets you simplicate and (probably) add lightness as a side-effect. Are the fuel tank vents out at the wingtips? how do you sstop them from siphoning if the machine is parked leaning? (On uneven ground.)

How do you prevent ethanol or petrol attacking the epoxy resin of the tanks and sump????

Knowing inverted flight is not part of the operation environment of the dark aero: How would the fuel system/engine react to an inversion?

In Europe(I guess Italy) they make the ultrafast two seat aircraft called Risen. Please note, with 100hp Rotax they guarantee the top speed at sea level 320km/h (173knots) and with turbocharged Rotax 915 -142hp they guarantee maximum cruising speed at 16 thousands feet 450km/h !!! (243 knots ) !!! Will Dark Aero be able to achieve the same velocity with much stronger engine ??? Risen has got the ultimate aerodinamics IMHO. Extreemly efficient and it is all carbon fiber too. What I like about Risen compare to Dark Aero, that Risen is not using any metal(aluminum) honeycomb, but rather materials which can never ever rust.... On the other hand what I like about Dark Aero is the gear(looks strong) and the 2 baggage compartments.

I might have used something more like Dacron, Aramid, Dyneema, etc. for a fuel sump under my legs.

You guys chose to go against a fuel selector valve & said you were sure the fuel transfer rate was within acceptable margins, could you expand on that? Does this design mean that if one tank has a higher head pressure than the other, it will flow into the sump faster, automatically balancing the tank levels?

You guys seem to be on your way to be a younger version of the Patey brothers. Great work! Take care and don`t forget to make sure your hat still fits. lol

Not worried about vibration on the fiberglass mounting points over time? Why not aluminum? Weight?

Why not using check valves to simply stop transfer between tanks?

For what it’s worth, can you pressurize the fuel system so it supplies fuel equally from all tanks simultaneously?

Excellent. The only thing is if your empty weight is 750lbs, and your tank is 77 USA gallons. Plus oil/fluids, that means useful weight is a nekked 90 pound single pilot.

I didn't catch how you ensure equal drainage from each wing.

It seems like going with a fuel selector could still be better than this. Most pilots are used to switching tanks and I think I would trust myself more doing that than a bunch of valves and piping and tanks, etc. Even if you run a tank dry, the engine slowly starts sputtering, switch tank and it comes right back to life.

Please, more if such deep tech stuff👻👻👻 You all my Hero

Cool!

why not one way valve to eliminate fuel transfer back to the wings?

just wow

this might just be me ..... but ..... why exactly do you not have oneway valves from the wings ?

12:33 Was the testing being done with real gasoline?

These videos have an incredibly similar vibe to engineering explained's videos

Fantastic presentation and discussion on the development of your fuel system to power the engine in Dark Arrow 1 Takeaways * Fuel storage and its effect on the centre of gravity. * Benefits of a sump. * Composite carbon fibre moulding. * Petroleum and fibreglass * Gravity and electric pump delivery systems. 🌏🇭🇲

If you’re worried about fuel transfer why not a ball valve?

Not for nothing but, I didn't notice any accounting for inverted flight or 0 G (Like a Flop tube) Etc...

Wasn't this aircraft supposed to be in the air by now? When is the first flight?

Are the fuel drain ports serviceable with standard components? Fuel drain ports routinely leak.

how do fuel systems work for like fighter aircraft where they pull all sorts of positive and negative G's?

you boys have set a new standard for over engineering

Wonder how military aircraft manage to pump fuel in negative / neutral gravity environments

Second design is always better...however those check valves vent and fuel are potential failure points....KISS

Will it be possible to fill one wing entirely while the other is empty?

When will the Dark Arrow Fly ?????

"What happens when a design fails?" It ALWAYS costs a LOT of money and sometimes people die. Having spent 25 years designing and managing the Engineering design of products I evolved several design rules. 1. NEVER, EVER let an "industrial designer" DESIGN products. STYLE yes, DESIGN NEVER. 2. ALWAYS have a Design ENGINEER design products. A Design ENGINEER MUST HAVE knowledge of all the production parameters of all the production processors required to make all the component parts of his design. Industrial Designers are concerned with the aesthetics of a product and some hapless Production Engineer is left to sort out their mess. My design rules for my Design Engineers were : 1. Design the assembly to last forever - amen. 2. No failures permitted - whatsoever. 3. No adjustment both on assembly or in the field permitted - whatsoever. 4. Absolute minimum of fasteners permitted WHICH MUST BE IDENTICAL TO EACH OTHER. 5. Top down assembly 6. Poka Yoke for assembly - physically impossible to assemble a part incorrectly. 7. Absolute minimum number of parts in ALL assemblies

😻

engineering standards..ie.. trial and error