It's remarkable to see just how consistent the entire skin of the aircraft looks, the machined tooling has paid off so well. Most aircraft of this scale have noticeable waves and irregularities just all over the surface

A&P pilot here, can’t thank you enough for all of the knowledge you’re giving! Keep it up and can’t wait to see the first flight!

This whole project is phenomenal. I wish you lads the very best of luck in the future!

One of the potential problems i have concern about is the spin recovery characteristics. The split rudder and location of the stabizer and elevater seem to be in positional relation ship to the rudder to cause "blanking" of the half rudder because the opposite half stays in neutral

We designed split rudders into the Lynx suborbital space plane we were developing at XCOR for similar reasons- it allows speed brake function and also was much simpler to actuate given their locations at the wingtips. We were also able to include a slight preload against the stop to provide greater resistance to flutter, important in a supersonic aircraft.

Always a great presentation… Tungsten makes an interesting choice. Density, and doesn’t corrode at ordinary temperatures of aircraft operation…. And not soft like lead. There is a recent AD for these elevator balance weights on a popular airplane because the weight was cast in a tube… and corrosion formed between the lead and the tube…. The corrosion forces expansion and the weight tries to fall apart. The problem took 20+ years to appear… but, once started the rate of oxidation increases, exacerbating the problem… Go DarkAero! 😃

You might want to consider a lockout for the split rudder for takeoff and climb. Canard flyers of various makes have had issues during engine outs of panic stomping on both rudder pedals, exacerbating the emergency. This is of course, alleviated with training. Also, a lockout would keep the passenger from inadvertently inputting while shifting their position, ect.

Really proud of you guys, I have been following you guys for 3 YEARS. If I get a visa to the US, I must come and visit you guys. The consistency is amazing.

The split rudder is so sick

I never tried the split rudder although I thought a lot about it. I have flown canard aircraft so I understand the speed brake part of it. Good job! Also it looks like you have some differential in the ailerons. Very good! Something I did a lot was flattening and widening the aileron counterweights so they tuck up inside the wing tips only when the aileron deflects down but the weight enters the wind stream when the aileron deflects up. This adds some parasite drag to the to the up aileron side of the aircraft thus reducing the amount of rudder required to maintain coordinated flight. It's good to see some young people that know how to think out good design. Keep it going and be careful. Thanks for the videos!

I used to fly the SAAB 340 and it had the most amazing redundant elevator system. Basically the left control column controlled the left half of the elevator and the right control column controlled the right half of the elevator. Normally they'd work together as one unit as there was a friction and mechanical plate that meant that if one side moved the other side moved as well. But crucially if part of the system jammed you could overpower the linkage between the two sides and still be able to operate at least half of the elevator. I always thought this was an amazing way to provide redundancy.

Great explanations and great looking airplane! Reminds me Mike Arnold's AR-5. Thanks a lot for sharing

The independent rudders are great. A very safe way to operate a speed brake without forgetting the boards are out. Yes, this happens, even with highly trained and experienced airline pilots they forget to stow the speed brakes.

Nice, heim joints, bell cranks and torque tubes, with not a whole lot of translation, so backlash should be minimal. You might want to also mention that the control surface weights, by projecting up into the airstream forward of the hinge point, also help manage control forces at higher airspeeds. The split rudder works VERY effectively as a speed brake, I use them this way all the time on my Cozy. I am curious what you're using as a rudder return spring - it looks like you're using push-pull cables to actuate each rudder, but I don't see space inside the rudder for a spring assembly - is it at the pedal end? If so, how do you plan to prevent buckling of the cable in push near the pedals if there is resistance at the rudder end? You'd need a decent sized spring to overcome the friction of a push/pull cable that long. Do you engage the brakes master cylinders only after you get full rudder pedal travel? How do you ensure you can land with the rudders deployed, but without the brakes deployed? (I'm assuming the nosewheel is full castering?) Lastly, I didn't see the roll servo, I'm curious as to where it's going to end up - it looks the only practicable place is behind the seats?

Great video, as always. In addition to clearly explaining the basic operation of your control system, I especially liked how you quickly touched on the considerations that went into the design; such as goals to minimize friction, backlash, compliance, and weight while also ensuring easy of service.

Very interesting rudder design, really clever double identity for a rudder. However, even though I don't see this bird doing dive bombing, the dive bombers in WWII also had an air brake, which didn't work until they poked it full of holes. Before the holes, the dive flaps ripped themselves off the airplane in some dives. There's going to be quite a vacuum in between your rudder panels. They're also small, unlike the surfaces of a dive brake, so making them work without unexpected consequences should be easy. Holes near the very front of the control surface should do, and won't interfere with the forward flight aerodynamics of the surface, but it will do the pilot and structure a favor. They can be made as decorative as they are functional.

Ngl, I love everything about the split rudder aside from the control scheme you've selected. Conventional rudder pedals (push one and other moves opposite) with a seperate speed brake lever similar to what youd see on a jet's throttle quadrant would be much better as far as avoiding inadvertent speed brake application and making the transition from other aircraft more seamless.

The Long EZ 'rudders' are somewhat required to be airbrakes, since they use a different principle to normal rudders to yaw the plane. Normal rudders apply lateral lift to the tail to pivot about the center of gravity. Since the Long EZ rudders are more to the sides rather than behind the CoG, the force required to pivot around the CoG is almost straight backward, ie, drag. And they need to be differential so that their is a net torque. If the EZ rudders were set up to act in unison, in the same direction, you would find that it would barely yaw.

Interesting rudder/spead brake. One thing I wonder about is propeller slipstream. On the Rutan canard airplanes the vertical stabs and rudders are outside the spiraling slipstream. On the DarkAero, it will be in the slipstream. I'll be interested to see how you deal with that, as well as rudder trim. My understand (which could very well be wrong) is that on the Rutan canards, the rudders on the winglets is more about creating drag rather than lift. Same goes with split style of flaps on other airplanes. I'm not an aeronautical engineer so I might be all wet... I'd like to see your split rudder act more conventionally with the rudder pedals and have a separate mechanism to split them. Kind of like the A-10 ailerons do. Hmmm... Or.... Leave the rudder conventional an put the speed brakes on the ailerons just like the A-10's! Keep up the good work.

Man. She is really coming together nicely. I really can't wait to see how that split rudder works out. Seems like a great way to add drag when you want it to slow down such a slippery plane.

We need so many more videos. Just normal everyday stuff. These are awesome

Every one of these videos teaches me something. You make complex concepts understandable, and most importantly, you give your audience credit for having enough intelligence to follow along with you. Much appreciated.

What about ICING inside the split rudder design? Will you test the push force overcoming ice adhesion? Another option is adding heat for safety. Love the concept, but Ice and Breaking concern me.

Such a gorgeous plane

As always the ailerons will create some adverse yaw that will have to be counteracted by rudder. Unfortunately the split rudder is going to cause a lot of drag during routine turning.

thats awesome! i have to put this rudder into my next rc model thanks!

I have now watched every one of your videos, some more than twice. Its wonderful to witness the evolution of modern design and materials taken to their absolute limits for your mission. The videos are so informative, easy to understand, and the plane is absolutely gorgeous. When it comes time for a DarkAero II, how do you feel about a plane with a 55mph stall speed, fixed gear, fixed pitch prop, 200mph cruise, similar mega-range? Come on, add a couple of feet to the wing, a couple of inches to the cockpit, use that UL520T so we can outclimb the weather - this will be an rv-14 killer. AKA, something us mortals can safely handle and still get insurance for (not to mention have a better resale value)... Just food for thought, keep up the good work, and keep the videos coming.

I didn’t hear anything about designing out flutter? This is of great technical interest to me. It is also the practical speed limit for many airframes, assuming they have lots of hp like this one. Would especially be applicable to high powered turbo normalized aircraft

That is a pretty sweet looking plane! ✈️

Your project is next level. Love it!

Great video as always!

You guys are SO LUCID. Actual role models

Is there an expected loss in rudder authority with your design compared to conventional designs, since only half of the rudder deflects with say a right rudder input. Wouldn't the fact the left half of the rudder remains within the line of the airflow "block" some of the airflow from adhering to the interior side of the deflecting right rudder and therefore reduce effectiveness?

its been an inspiration watching you guys since the beginning of the project , as an engineer also please do discus on the safety against lightning strike especially when using CFRP.

In 1965, the Payen Arbalète PA60 was already using such a system that inspired Rockwell for the space shuttle...

I like the split rudder as an air brake. But I hope you have considered how the airplane will react in flight with only half of the surface deflecting? With this, you are splitting the airflow, creating a void of air forming low pressure pocket behind the airplane. This means any time you use the rudder (usually at low speed TO or landing) you are adding a lot of drag, which could decelerate the plane at a critical moment. Another negative aspect I foresee is that while one side is deflecting, the other side is still in place, acting as a vertical stabiliser. I believe this will negate a lot of the effective yaw control and may require a lot more deflection to get an adequate response. Just my thoughts. Would love to see how you guys have tested this concept.

Clever design choice with the split rudder/airbrake. For better or worse, this style of airbrake doesn't reduce lift when deployed. Wing spoilers have the benefit of increasing tire traction, although I suppose they have their own concerns, such as difficulty in packaging without a drag penalty. I'm curious how the split rudder's drag compares to a hinged rudder at modest deflections (e.g. trimmed for P-factor at cruise).

I can't wait to see it in the air.

I really like the inclusion of the dual yaw rudders as an airbrake as well. glad i found yalls channel and congrats on all the progress

Beautiful thinking . It made me happy as same as seeing Beautiful paintings

You say that it's kind of complex but it's about the most basic way you could do it with hard mounted components. Nice work.

I would love to see the pedals in the cabin to see how the brakes operate with the split rudder system. Please include that in a future video!

The most advanced airplane 🛫 today 🛫🤙🏻🏆☝🏻💪🏼 looking forward to more videos ty

Regarding the split rudder.. my basic comments would be pretty much the same as the others commenting - interesting, but not necessarily a good idea. I fly a Long EZ, at much lower speeds what you will be flying. 160 kts, max. when descending with full power :) Except for takeoff and landing (65-90 kts) I don't use my rudders. No need for that, with the arrow shaped wings of the Long EZ it keeps straight, even at takeoff. If I try to use them, at cruise speeds, 128kts with my setup, it takes considerable effort to press down on the rudder pedal. I am guessing it will be for the DarkAero too, since a split rudder is not balanced at all. When used as an airbrake, in my Long-EZ it introduces a fair amount of unstability - both rudders don't have the exact same deflection - since I am pressing them with my feet and the airfow is not clean over them, at full deflection. I much rather prefer to use my airbrake that extends from the belly of the aircraft. That is also much more effective on a Long EZ. Though max employable up to 90 kts. If you haven't yet done it, try to find a Long EZ or other Rutan inspired aircraft (easiest with a side-by side arrangement) and try the split rudders for yourself. At cruise speeds, in a conventional aircraft you need the rudder to make coordinated turns. In a swept wing aircraft (Rutan style) you almost don't need it. For airbrakes, if you can deploy your landing gear partially and if it doesn't interfere with the aircraft stability and controllability, the landing gear would make a wonderful and substantial airbrake, with no weight penalty other than the control knob for it. And I am sure you have made the calculations - what forces are acting on the split rudder at Vne and the pressure you need to push the rudder pedals with you feet.

8:15 i've always wondered why more planes don't have that, its like a really easy way to reduce speed. glad to see the team incorporating that design into your aircraft though, keep it up.

This project is hugely inspiring, you guys rock! Cheering you on

So impressive. Range and cruise speed are unmatched. I'm a simple RC pilot. But enthusiast or not, who doesn't think this thing is awesome!?!?

You should reconsider the current rudder actuation. As @aaronhammond7297 mentioned in a comment a few days ago the Long EZ 'rudders' are somewhat required to be airbrakes because the force required to pivot around the CoG is almost straight backward, ie, drag. Which is not true for your design. Every time one will actuate the rudder it seems that it will also create some serious drag, due to rudder's size. Considering that you designed the plane for speed, that's a major oversight. Sometimes being different is not being better. You can keep the split rudder design, but the halves should move together, unless the brake is actually wanted and applied intentionally some other way.

Nice one! Guess next month the video will be about flaps and trims? And what about the antennas? I’m really curious about those…

Can't wait for the first flight. Amazing work guys.

The side stick is very cool, can't wait to see the video where you explain the autopilot system!

Your explanations are always so good and easy to understand, great project!

How will you handle constant yaw inputs in cruise flight? Won’t a constant split be inefficient?

Always informative guys!

I am predicting the rudder will be changed after flight tests. It would be more sensible to let the split rudder stay together as it moves left and right and only opens up when a speed brake is actually required. Easy enough to do with a mixer. On an aircraft designed for utmost efficiency, getting a drag brake opening every time you use the rudder makes no sense.

This is pretty slick. You combined the dual rudders of a Rutan VariEze into a single unit. 👍 Edit: I should have finished watching your video before I commented. At the 8-minute mark you talk about the VariEze.

The prototype 1932 Beech Model 17, later named Staggerwing, has a split rudder. This feature was not carried over into production staggerwings. The prototype Model 17 is in the Beech Heritage Museum in Tullahoma TN. It will be interesting to see your rudder performance results compared to what Beech experienced 92 years ago.

You guys are awesome! Everything is very well thought out. The split rudder is a great feature. Using it to slow the plane down is very nice. I have to ask, in turns, does the other half, the straight half, hinder the turning ability of the turning half, enough to notice? Do the halves open up enough to maybe offset any drag? Again, great job! I hope to have the money to buy one of your airCRAFT one day! Take care

Very nice project. I would not do split rudder, I think it mostly generates drag not yaw moment. For EZ planes "draggy rudder" works because of different location of the rudders.

You may have covered it elsewhere, but I would be interested to hear about the flutter considerations for your split rudder assembly.

Very cool, congrats on the innovative design! I'm still looking forward to HS taxi testing/ TO roll testing. I looked at the similarities/differences between the DarkAero and a TBM for TO roll (for P-factor). They are somewhat (loosely) the same. The TBM has a large rudder, and needs it to hold center line on TO. It will be interesting to see if the split-rudder will also hold center line at full TO power. I'm rooting for you guys! 8) --gary

Very cool. You didn't mention nose gear steering. How will that work? Maybe include with the secondary controls discussion?

This plane looks so good, love your vids, thanks

Cool. Please get into more details.

I'm excited for DarkAero! Approximately when will the maiden take place?

I love your work. Big fan from your start. But the split rudder makes much more drag than a standard one. You can accomplish the same load but in expense of much more drag than a standard control surface.

TECHICAL PTS ONLY Your rudder is just skin. It should've ribs. Otherwise, it gonna collapse under aero load, locking its hinge, making it catastrophic. Too many linkages providing failure pts. Trim tabs is another set of failure points...Instead give trim tabs on stick like RC model Longer control horns proportionally minimize backlash.

Tungsten? Depleted uranium would be more fun. It's good enough for a 747! ☢

Was wondering about flaps. Glad I'm subscribed (11:40).

Have you thought of including a toroidal propeller. Reduced noise, higher performance. Amazing.

the tail design seems really interesting, I guess that somehow reduce drag?

I am really not impatient for this project to be done, as your videos are so educational and well made. Thanks !

Can't wait to see it fly.

excelente video, keep it up

My first thought is that I hope that the right pedal is for the right flap the left pedal is for the left flap so that if you push them together it acts like breaks

Impressive work.

Cant wait for the maiden flight! Do u guys have a date in mind when that will be?

Love these videos. Would you be willing to do a video on the business model/plan? Curious how you see the DA fitting in around the Lancairs and RVs of the world

Is there any increased icing risk in the split rudder?

Holy mother of laminar flow look how clean that plane is!

I barely started watching and I have to say, what a beeeautiful airplane! So aerodynamically clean! Interesting ruder/ brake; I think I've seen this idea before in old airplanes. Congratulations!

Yes. Serviceability is flight critical!

Looks las though it'll be a nice, crisp handler. A little bit of friction in the systems isn't bad as a damper of oscillations. It will be interesting tosee how you handle trim, and how you achieve differential on the ailerons.

Please explain the split rudder more. I see impact force vs lifting force as one side stays flat (stream lined) while the other is inducing drag. Is the concept the same? Are there efficiencies in stabilization with the split rudder?

Amazing video as usual. Just curious to know which camera do you use? The auto focus is sharp, fast and accurate.

Can you talk a little about how the split rudder is able to handle the high air drag forces when both sides are out?

The „torque“ tubes actually designed here, are not really loaded with a torque load, as they do not revolve around an axis that lies in the center of that tube but are rather „bending“ tubes. I would like to see that working as well, but i am a bit afraid that under stress, there will be too much flexing in the controls… flight testing will tell. But my greatest respect for all the design and engineering work done here and the nice documentation… out of your videos i took the inspiration to also use Onshape for my projects.👍🏼 Great tool!

2 questions regarding the rudder: Wouldnt the empty space between the rudders cause extra drag on high speeds? as the air stream will be split in half? at some speeda this migh act as a lifting surface no? is there a possibility that the "air brake" will act as an elevator if the angle of attack is not perpendicular to the "rudder"? say on final?

I would glue that split ruder together... Other than that, it is looking very good.

Do you have a rudder trim system ?

Is there an interlock of sorts that keeps the rudders from going into speed brake mode while in flight?

How bad is the performance loss during initial climb when using a lot of right rudder? It seems like you’d be trying to climb with the speed break basically partially deployed if you have a consistent rudder input in

You've probably already answered this but how is trim done?

I have no doubt the split rudder will be 1) Easy for the pilot to operate, 2) It will cause the desired yaw moment. However every deflection of this rudder will *also* impose the same drag that you intend to get in "air brake" mode. I'll acknowledge that the stagnation point in cruise will be proportionally small with small control deflections, but you're still invoking a braking function every time you deflect the rudder. The VariEze design, which continues to be used as an comparable example, does not impose this penalty. And of course with the shallower spar per rudder you're exposed to aeroelastic risk via lower torsional strength. Regarding elevator counterbalancing are you not also employing a counterweight arm inside the fuselage to minimize twisting moments on the elevator?

Love the plane! One question though, how do your wheel brakes work? Guessing no toe brakes?

what are you guys doing about confliced input /panic input on the rudder? you might just end up with a huge speedbrake deployed at takeoff

How does the roll not bleed into pitch control? When you move the stick sideways, it seems that the pitch linkage would move a bit forward?

I didn't see any mention that the long torque tubes through the wings, at the cabin, don't pivot at the tube? Hard to explain, and I don't have the correct vocabulary to properly describe, but watch closely at around the 6:00 mark. The inboard bell cranks are anchored on one of the ears?! Is it very weird that the inboard ends of the torque tubes move up and down in space?

One doubt, the split rudder can in thesis act differently because both sides would never act equaly and cause yaw?

Carbon fiber wrapped aluminum tubes, should do the trick. Please get/use a better flashlight/headlight -- something with great CRI