There are two issues I think you skipped or at least did’t list : - traditional airbrakes also reduce the wing’s lift, which greatly increases the drag - During fast flight some low pressure occurs at the rudder’s trailing edge. Will the twin rudders be sucked, open a little and therefore increase drag ? I suppose that that’s the return spring’s job, still it may harden the rudder’s response to the action on the pedal. All together your aircraft is very well designed and excepts too many “glued” components, you seem to have done a magnificent job ! Congrats 😊
That rudder is nothing but an outdated and obsolete tech straight from the 1930 design books. List 1 benefit of that design, and I'll write you book on its drawbacks. Also the high speed force feedback can be tuned with winglets, that's not really an issue at all. The problem is #1 you don't need to have airbrakes on the wings, especially on a superlight, a simple flap would make the difference you need. #2 the wings DO have airbrakes with the flap design used...There are so many fundamental design errors in this airframe I can't be bothered to spend more time on it.
I admire your drive and passion to start a project like this. As an engineer who loves to innovate anywhere I can, I like your ingenuity of integrating a speed brake into the rudder. I was considering a similar idea on my plane, except as applied to the pivoting canard instead. I have some friendly advice I'm sure you don't want to hear from some random nobody on the internet, but I did notices two issues with your design that would become evident on the first round of high speed taxi testing, It is an easy fix if a little hard to explain. 1. Your split rudder design is not dynamically balanced to offset the extra control force required at your high cruising speed as the rudder deflection is increased. A balance isn't always required, but if in the future you find one necessary it can be incorporated with a dorsal horn balance at the tip of the left rudder and a ventral horn balance at the tip of the right rudder. 2, The second issue and by far the more important, is the intent to connect the left and right rudder flaps separately to the left and right rudder pedals with the speed brake function requiring constant force from the pilot on both pedals to keep the rudders open. Something which would increase pilot workload both physically and mentally during landing procedures. The fix for this is to implement a rudder control mixer device similar to a v-tail Beechcraft controlled by a distinct ratcheting speed brake lever in the cockpit. This would in effect be as simple as piece of steel C-channel with a hole on either end allowing the respective left and right rudder cable to pass through either hole. The plate will have a pivot in the center connected with a push/pull rod to the ratcheting control lever. When the control lever is pulled the plate slides down the rudder cables until it impinges on knots or clamps placed on the cables thus tensioning the portion of the cable connected to the rudder flaps, this motion will simultaneously open both rudders. The further the latching lever is pulled, the more the rudder flaps will open and thus a high amount of drag is produced. The extra control force resulting from the increased drag is taken through the mixer pivot anchor into the airframe, thus the increased control forces produced by the increase in drag are not felt by the pilot through the rudder pedals. Rudder control through the pedal remains unaffected even when the speed brake lever is pulled due to the speed brake control mixer incorporating a pivot between the two rudder cables. If the pilot adds additional input to the right rudder pedal the mixer will pivot about its center and let off a equal amount of tension/slack to the left rudder cable and vice versa. The clamps placed on the cables with be positioned such that when the speed brake lever is in the released position, the cable clamps will not impinge on the speed brake control mixer even at full rudder deflection, thus preserving independent control of either rudder flap.
Good luck with the split rudder, I hope it works for you right out of the box. Depending on what degree of offset you put in the thrust line and vertical stab., will determine the amount of rudder needed in take off and climb. Some of the light aircraft I've flown have required considerable rudder throughout the climb phase, and I do have some misgivings about how the extra drag of the s.r. might affect climb performance
I'm a VariEze builder/pilot and love all the innovative techniques and features you're putting in the DarkAero. I'd like to share my experience with the independent rudders on my VariEze. At high speed they are difficult to use as speed brakes because of the yaw produced by even a slightly uneven application of pedal pressure. It's pretty sensitive because of the high airspeed and takes concentration to keep the airplane tracking straight for the minute or so while the speed brake is needed. For that reason the only time I use the rudders for speed control is on final approach when I realize I'm too high. And even then I find the feature to be of limited use because of the attention it takes to control yaw while modulating the drag to get me back on glide slope, in addition to all the other things happening on short final. The extendable 'belly board' on the VariEze and Long-EZ is a lot more useful since it doesn't require attention after being extended, allowing the pilot to focus on other things. However, it can only be used at lower speeds such as in the landing pattern.
May I say thank you for the excellent series of videos about this project. I have been a commercial pilot for over 30 years, mostly jet aircraft, and speed brakes were an essential part of the flight control system. There is a saying in the jet pilot community, “you can go down or slow down, you can’t do both”. But that was high speed jet aircraft. This is a high speed low drag propeller aircraft and there in lies the difference, the prop at low power is a very effective speed brake. Can I suggest this split rudder is a solution looking for a problem. It is very cool though...
Exactly. For a design supposed to be operated at top speed, as is this is a feature that would actively prevent it from ever reaching said speed stably.
@@meusana3681 Some really questionable design choices with this aircraft. Every time I watch one of these videos it's like they're trying to do everything opposite of what the fastest and most efficient aircraft are utilizing. No winglets, split rudders, split flaps...I just don't know what to think of these guys. About the only aspect I see that could make this aircraft perform is the fact that it might end up being really lightweight due to all the things it lacks.
Yup. It's oceangate all over again. Some really shoddy and outdated engineering coupled with new age materials and suddenly everyone is raving that this is "new tech" for some reason. For this reason, I don't think much of them. And I bet they have heard this argument from internal engineers too, just didn't want to listen. Split flaps and split rudders were tested and became obsolete in the 1930s (basically only USSR used split flaps in WW2, and no one did split rudder even thought the tech was heavily tested). Why are they even pretending they're doing something new here? @@Skinflaps_Meatslapper It's basically a superlight with out of the box controls...Almost like they focused on the "how" for so long they forgot about the "why". Also the exact thing that's supposed to make this aircraft good is the same thing that will make it suck. Light airframes hate drag, any amount of sideslip is gonna tank its efficiency and speed. Apply rudder and it's like a car driving into sand.
optimizing a high speed aircraft, yet one of your primary control surfaces can't help but be a speedbrake under normal conditions. Every time you're not in absolute neutral position, you have deployed the airbrake to an extent.
I have an idea that may work.. maybe incorporate magnets to keep the split rudder closed, so in cruise where minor rudder is required, it acts like a conventional rudder. If you push both pedals, then it’ll overcome the magnetic hold, split and give you air brake function.
If the opposite hinge allowed the non deflected rudder to do that, the suction from the vortices would pull it back with it anyway, no need for magnets.
How about electromagnets so they are easier to disengadge..... you are already fighting both aerodynamic and spring pressure...the weight could be an issue. This design as presented looks a little vulnerable to flutter in my eyes... there are no balancing horns or surfaces.
Permanent magnets would make the action "sticky" - that would be very undesirable. Electromagnets would add complication and dependence on power supply, which would also be very undesirable.
I was introduced to this aircraft by Michael MD (thanks bro) ... been following Scrappy, Raptor and now DarkAero. Oh yes... I am from India and love flying stuff. Was a Microlight Trike flyer for over two decades. (just saying) Hello DarkAero! Cheers
The DarkAero gear is similar in gear extension geometry to the SX-300 landing gear in that it slants forward from fuselage to wheels. But the DarkAero's gear is less complex. Nicely done guys!!
Disrupting airflow over the wing is one of the reasons a wing mounted airbrake works well as an airbrake. By spoiling lift, the aircraft needs to create more lift via AOA, thereby increasing induced drag, so it's a twofold effect. The amount of fuel you save by not adding airbrakes to the wing probably amounts to a gallon total.
Saying vari-EZ's have split rudders so yours will be OK is just not correct. The split rudders on those canards are designed to create drag force far away from the CG to create a yawing force. Your split rudders will create more drag than they do lift, just like split flaps. You want a rudder in a conventional layout to make a lifting force to create a yawing moment. Creating a lot of drag won't work and rudders are critical Additionally, comparing to the shuttle, whose rudder functioned normally but could split in half for air brake functionality is also a bad comparison. Good luck. Sometimes being different is just a waste of time.
I like your guy's analytical approach from design to fabrication, and of course, including the cool factor, I mean, that's what flying is right? However, you've overlooked stating what I believe are the the two most critical factors when comparing the split rudder type to the fence type..... No additional control to have to remember where it is, how to use it and then also remember to stow it (gear up landings come to mind...). Frankly, when you think about it, it's natural instinct to stomp the rudder pedals for braking, right? Now, most importantly, you've eliminated the possibility of an asymmetric drag and lift spoilage condition if only one fence were to deploy due to a mechanical failure.....How would that literally end up? Brilliant guy's! Keep up the great work!
Love following your progress. I hope the spring mechanism is well tested and bulletproof. It seems a failure in this mechanism would lead to catastrophic flutter.
What about controllability and spin recovery? In the canards, the rudders are at an extreme lateral position, therefore differential drag is sufficient for yaw control.
Great video, I have experimented with split rudders on RC aircraft and another big advantage is they don’t flow turbulence on to the elevator / rudder like inner wing or fuselage mounted ones do.
This very well might be my next build. Besides being composite with a retract, this split rudder idea I find the most appealing. I'm guessing you'll be adding a bit more structural reinforcement than what you displayed. Also any thought of adding trim without inducing drag? It would have to be able to move past center while closed.
Justin Wylie we will probably initially fly the prototype without rudder trim but there are a couple options we are considering. One would be a fixed position ground adjustable trim tab. Another option would be an in-cockpit adjustable spring tension system that applies a light tension to the rudder system to give a small rudder deflection. There are commercially available trim systems like the latter option available for Vans kit aircraft.
@@DarkAeroInc Both options would probably work. I have Aerosport's tension spring system on my 10. The only issue I see on a system like that on a split tail would be that compensating either way would induce drag.
@@_Stark That is also an issue with deflecting a conventional control surface to trim. At small deflection angles (trimming) the drag increment is very similar between both style of control surfaces.
@@DarkAeroInc It works, but I also have a yaw damper so I only really use it in extended climbs. The only downside is being 100% mechanical there's no trim guage.
Great presentation. Aesthetically, I do find the DA1 rudder pleasing. Speed brake use is often periodic in use, so an atypically designed deployment may have less operator consideration than say, a wing flap or a flying control surface. Practically speaking then, does the split rudder speed brake involve the pilot simultaneously depressing both rudder pedals? I suspect the pilot learning curve will be steepest in operating the speed brake and commanding yaw at the same time. I’m thinking of left yaw in a descent with speed brake. Actually, this leads me to the questions of engine mount cant and tilt and rudder offset. Does DA1 have one or both? How much yaw will be induced by power on pitch over?
Not a pilot, but I'm just wondering if there are situations where you need to have reasonable rudder authority while the speed brake is on ... And if so, will this design be ok?
That's an easy problem, just don't fully deflect the rudder surfaces when used as a speed brake. This will allow one side to increase deflection and the other side to reduce deflection, creating an imbalance, similar to the way mixed control surfaces work. They did the same thing on the shuttle. I don't see this being a great design to live with on a daily basis though, as there will only be one speed in which rudder correction won't be necessary, and even then you'll still need occasional nudges to keep it tracking straight. All other speeds will require some degree of deflection, meaning the rudder will always be a speed brake to some degree except at that one speed and throttle setting. Even the shuttle rudder operated like a normal rudder with both halves following each other until they needed a speed brake, and only then did they split. I have a feeling that after some flight testing, they're going to redesign the split rudders to follow each other for at least the first third of their deflection before splitting. That should cover most of the envelope in a normal flight regime so they're not constantly paying a drag penalty for being cute.
This is interesting but the control method seems like it would be cumbersome. A separate speed brake handle and mixing box to still allow rudder input with the speed brake deployed would be best IMO. Another thought to eliminate the drag when it's not needed, is to have the split rudders mounted in a carriage of sorts that's then controlled as a single control surface, so the rudders only split when the drag is needed.
A few questions - how will the prop slipstream interact with the split rudder design? From other videos I gather you have pitch and roll trim but don’t have rudder trim. You may or may not need rudder trim to counteract slipstream, but I’m guessing with a powerful engine on a very light airframe, you will. If you do, won’t a split rudder translate into an effectively “always on” speedbrake? Is there an airspeed limit for speedbrake deployment and if so how is that implemented? What happens if aerodynamic forces overcome the spring return-to-center on the rudder?
A big disadvantage seems to be that pilots might by accident apply speed break while actuating the rudder. Say you are in a difficult crosswind approach and have to change the rudder position all the time. This includes the rudder crossing the neutral position. Neutral crossing with the split rudder system requires that the pilot lets go of one rudder and than pressing the other one at this moment. If the timing is off or the pilot keeps some pressure on one of the rudder paddles, he will actuate the speed break - by accident. On a normal rudder the mechanism fundamentally only has one degree of freedom so this much more intuitive. To me if feels like if you want make this work this sh The cost does not seem like a good argument to me either because you can simply, make the break yourself out of carbon fiber as you do with the rest of the aircraft.
Did you consider a standard rudder function with gears to perform the split for speed brakes? The rudder halves could pivot left or right as one until for yaw control and trim without inducing excess drag and the split speed brake function could be controlled with a pull handle like a parking brake The speed brake would then be independent of pedal movement and the gears would ensure equal application. two 1/3 arc meshed gears should be sufficient for speed brake deployment and springs on the hinges would force the shells together on the ground and aerodynamic forces would aid that function in the air. Speed brake are a once a flight use item, so it should be better to not compromise rudder overall drag for the rest of the flight regime to provide that function.
Adding it to the elevators would probably get a bit dicey mixing it in with pitch control. The split rudder was mechanically really easy to implement and we had a little bit of a foundation to work off of looking at other similar implementations like the ones we mentioned in the video.
How susceptible would that design be to gust damage while parked, and , would you need to employ a gust lock whenever parked or possibly an internal locking bellcrank?
Out of curiosity, under reduction of parts principle, did y’all consider a V tail? and if so, is it possible to do both as a split rudder in that style? I bet there are some different lever arm considerations to apply similar self induced drag purposes, but in general, same applications are available in less parts no?
Have you considered adjustment on the centre stop to enable trim on the rudder, should be simple-ish could be light weight and improve performance by lowering drag
I like your commentary on why it's lighter, but for PPL, how often do we have to use a speedbrake? The traditional rudder is on a pulley system, so the left and right rudder pedals are mechanically linked, while for your split rudder, it's not and we have to consciously lift one foot and press the other. However, I think it's interesting that this creates both a risk and a redundancy. With two rudder linkages, there's twice the opportunity that one of them will break. However, if one breaks, you're not left fully without yaw authority as you can use the other one. If the left rudder breaks, for example, then you can still fly by only making right turns using the still-functioning right rudder.
Good Point Alan. I wanted to add that I am not a big fan of both the split rudder and split flap system. Maybe the guys at Dark Aero can answer this question. When using the rudder, there is going to be a lot of drag and I would assume some buffeting associated with that. Just because the airplane is designed for high speed cruise flight, doesn't mean that pilots don't want to have fun and fly some maneuvers around clouds, formation flight, etc. And I personally, would think the feel of the rudder pedals would feel odd when pressing on the left pedal and the right one does not move backwards in sync with the left pedal. I would also think it would be easy to inadvertently split the rudders and act as a speed brake in normal flight because the rudder pedals are basically your foot rest. For the split flaps. I have not seen that in any airplane since the 1940's or 1950s. I would have like to have seen a Fowler style flap to increase the wing area and lower the stall speed. I'm sure Dark Aero had a good reason for going with the split flaps. Also, looking back at some of the designs from WW2, notice they have holes in the flaps / dive brakes. These holes were an afterthought to solve the problem of buffeting when deployed.
How do you 'tune' the split rudder on installation and during initial flight test so that the aircraft flies 'straight' ? Do you have to rely on trim and if so, how is that accomplished, manually or electromechanically ?
The main disadvantage of this system is in my opinion that when your rudder is off center, you also have the speedbrake partially deployed, regardless whether you want it or not. But I'm not a pilot so I don't know how much of a disadvantage it means.
I'd make the split rudder an option to come later once everything else has been figured out and you have actually concluded that the usual means (draggy landing gear, flaps, prop in flat pitch) are not slowing you down enough. I'd just put the expensive speed brakes into the prototype and be done with that issue and see whether I actually need them.
Points, taken. Slippery airframes like this need a brake when in flight in a descent well outside the terminal control area where gear and flap settings would not be changed. For instance, the normal operation of gear and prop pitch in most retractable gear aircraft is usually, not until at or near the final approach fix. Roughly
@@user-tv5dt3nm9y I thought this to be the inherent problem of big engines with a limited cool-down gradient and pressurized airplanes. Those cannot significantly reduce the power on descent, else they would cool down too quickly, especially at high altitudes or not produce enough bleed air for pressurization. Turbo charged engines also need a minimum manifold pressure to keep running at very high altitudes. I would think that this plane allows cutting the power on descent.
Martin Renschler well there’s a lot to unpack in your statements. As far as the DA1 is concerned, I believe the concern is of how to go down and slow down in a time and space limited airspace. There are speed limits to consider, Vne, and maneuvering considerations like turn radius and bank angles, blending with other traffic, accelerated stall margins, and uncomfortable g-loads with a higher loaded wing. Lol, your significant other may not find 60-70 degree bank angles at 2-2.5 g as much fun as you do. I’m not going to touch the shock cooling mythology. Just how slippery is it? Look at the DA1’s cruise airspeed projections vs HP, its overall dimensions, the wing loading, and a clean, non-parasitic drag producing skin. To get your head around it, compare those numbers with aircraft of similar design goals out there.
The free-cantering nosewheel means that the rudder and differential braking are the only means of directional control after landing. I have the same question as others relating to how differential toe braking will work without the using the opposite foot for leverage. I also question how easy it will be for pilots to transition to non-linked rudder pedals. Not easy to remember to lift one leg while pushing down with the other.
We will probably initially fly the prototype without rudder trim but there are a couple options we are considering. One would be a fixed position ground adjustable trim tab. Another option would be an in-cockpit adjustable spring tension system that applies a light tension to the rudder system to give a small rudder deflection. There are commercially available trim systems like the latter option available for Vans kit aircraft.
I must have missed the part where you discussed the flutter issue. How are you mitigating flutter and how are you controlling the sidestick forces for the pilot?
Another point: most pilots fly with their feet resting on the rudder pedals, usually with a light constant pressure. Unless you build in in some considerable breakout force, you'll be flying with a drag brake the whole time. And if you have a bit in breakout force, I bet the feel when flying will be horrible. Just my thoughts.
Are the pedals completely independent (leading to this problem), or are they mechanically linked (so they they will not both deflect at the same time)?
Hey guys, that split rudder idea, while cool at first sight, may backfire at you - be careful. Split rudder system in shuttle, B2 and other military planes is carefully controlled by software, sensors and activated by precise machinery only in specific flight regimes. Your system is manually actuated and easily can be mismanaged in flight, and as someone using it in VariEZ mentioned, puts more workload on a pilot. Please consider removing or offer it as an option. And if you offer normal rudder with trim control - you will have my deposit to get in line for your kit!
I agree with you... Especially on their very first aircraft, they should be taking it easy with the "special" features, and maybe leave that for the 1.2 version of the plane instead. What initially matters is that the plane flies safely and predictably - flaps should do the trick for slowing down on approach. A complicated rudder system such as this will only bring delays. If the FAA has to approve any of this, I can only see it adding more time for certification.
This isn't supposed to fly in icing anyway. But with most symmetric tail surfaces, icing doesn't affect it's ability to provide balancing and stability forces. Some airliners don't even use anti ice devices on the tail surfaces.
What about spin recoveries? Wont the split reduce the lift the rudder can generate to counter a spin? I suppose drag back there could help but i suspect youll have fair amount of spin testing to do. Very cool though.
I agree with your thinking. In addition, the vertical stabilizer also has a fairly aggressive airfoil leading edge, along with an unusually high aspect ratio. This means there is a possibility the vertical stabilizer will stall at relatively small angles of sideslip, reducing lateral control even more. Most vertical tails have an AR of less than 2. Not~>3. This design will have more effectiveness at small angles, though, due to it having an improved lift curve slope due to higher aspect ratio.
won't this have more drag during high "p-factor" operations which require rudder? Extra drag while rotating for take off or fighting a x-wind doesn't sound fun. If it operated like a normal rudder AND had the split function that would be ideal.
sounds sketchy in a low speed crabbing situation where you want to bleed as little speed as possible while yawing the nose off. If you've got reserve altitude you're probably fine since your tail inputs will always bring the aerodynamic centre backwards. I do really like it as an airbrake design though.
Canard aircraft (i.e. Rutan inspired; e.g. VariEze, LongEZ, Velocity, Cozy) have the same setup and they simply avoid using much, if any, rudder input in such scenarios. Some of the big jumbo jets also indicate a preference for landing crabbed as opposed to attempting a low-altitude sideslip, and IIRC at least one of the POHs or airline manuals prohibits sideslip landings. Sideload on the gear isn't as much of a concern when you're touching down at ~1,500lbs.
@@ParadigmUnkn0wn the canards just have single direction actuation not exactly the same thing. And landings are not high pfactor scenarios. Jets don't even experience pfactor...
Horizontal Stiffeners on individual rudder splits might give more Stiffeness for better surface controls by avoiding more deflection of skin alone.. i.e. Normal rudder edge on inner sides- without affecting interfaying control mechanisms..
We will probably initially fly the prototype without rudder trim but there are a couple options we are considering. One would be a fixed position ground adjustable trim tab. Another option would be an in-cockpit adjustable spring tension system that applies a light tension to the rudder system to give a small rudder deflection. There are commercially available trim systems like the latter option available for Vans kit aircraft.
You guys are awesome...NASA and SpaceX might get us to other planets...but all those astronauts and engineers are gonna buy one of your planes to get to work!!!....
@@DarkAeroInc Do you have plans to allow for a yaw damper? I'm wondering if this might be helpful for creature comfort given how short the aircraft is!
We haven't made any video yet on our mold making process but we were just talking recently about how we think it would be beneficial to show folks what kind of work we put into for our molds and mold patterns.
Doesn't the split rudder create drag over and above a regular rudder anytime that it is used? That would be bad if you are in a near stall situation on landing and want to use your rudder? What am I missing?
CG => Pitch issues? Speed breaks are generally mounted close to the CG. By exerting a breaking force so far aft and above the CG are you not going to create a pitch moment potentially leading to a stall if not corrected with aileron input? Further, in the event of an asymmetric input (meaning you extend one more than the other) are you not going to create yaw + pitch up, potentially leading to a spin?
Nice idea but I believe your engineering is not completely thought through to the pilot work load. I think you need to implement a separate control for the speed brake function that deflect both rudder halves equally while leaving differential rudder input in the pedals. I.E. flaperons. It should be simple enough to connect a control to the bell crank to deflect each rudder surface equally for the speed brake.
The A-6 Intruder used a similar function at the tips of its wings. I don't know if they could be individually deployed to provide directional control assist.
There isn't one yet! But don't hesitate to send us a resume at info@darkaero.com.. As we ramp up into production, we will be on the search for full time employees.
Have you tested this on an actual plane yet? I think you'll have less rudder authority with only one side moving past center for yaw control. And you don't have aerodynamic balancing, so the control input forces have to be greater.
Hi guys! I’m not sure this is really related but: how does this split rudder works in case of a spin? Did you have the chance to simulate the spin tendency of DA1?
How many pilots would want a plane that could kill their passenger/s and themselves from not being responsive in overcoming even an incipient spin? Where is the efficiency in hauling a plane recovery chute system?
Control surfaces on high speed aircraft are balanced to prevent flutter. I don't see any area ahead of the hinge point to add counterbalance weight. Be careful on those first fast flights.
Interesting, didn't know that hondajet had a baboon brake. Not sure that's elegant engineering. But it makes me wonder, could tab style airbrakes on the wings work effectively as a rudder if placed far out on the wings? I hunch that it would express too much as drag but if the wings have a certain length, would it be... if you could forego a moving rudder, that would be elegant. If you take care of stability and trim with a static tail then it would only be for approach maneuvers where any slight inefficiency is worth the elegance. Also I wonder, indeed assume, that rather than a prominent vertical tail, it would be better to reach far back with a much smaller tail fin like a shark does. Even though a shark uses it for propulsion. If a little extra length on a skinny tail makes a much better plane then it can be worth ignoring the hangar demands.
How does this affect airspeed in critical slow speed produces such as landing in a cross wind or side slipping. Does the increase drag affect take off performance in a cross wind. Is there a reduce limit to allowed cross wind component when landing.
Wouldn’t you create a lot of drag when just using the split rudder as a rudder since the air can’t flow around the control surface? It would render the rudder less effective due to the air turbulence on the low pressure side?
It looks like you are using Aluminum hinges and rivets. Aluminum and carbon fiber can develop severe galvanic corrosion when in physical contact in the same component or structure.
Why not make the stabilizer skin bend at the line where the rudder starts instead of cutting it and using hinges? Couldn’t that be done by having right amount of right kind of carbon at the hinge line?
One suggestion. Make the wing tips easily replaceable. By testing various tip configurations you could gain 12+% efficiency. Of course only after you prove the rest. I Love your project and videos.
Does deploying the split brake effect pitch because it's the full length of the vertical stabilizer? It's hard to see from the video if it's wider at the bottom or not.
Thien Lieu a minor pitch change is possible when the speed brake is deployed since the drag center of the two rudders sits above the aircraft CG. This isn’t much of an issue though since pitch changes also result from extending flaps or landing gear or even entering a banked turn.
@@DarkAeroInc not the same flaps and gear are deployed with altitude air brakes may be deployed close to the ground in the flare would result in a hard landing or nose wheel collapse or worse
Loyd, thank you for watching and for the question. Galvanic corrosion is something we get asked about often. This is probably a good one to update our FAQ page with. In general, any of the aluminum present on the aircraft is electrically isolated from the carbon fiber. All the rivets used in the aircraft are stainless steel.
I think there is another human factors issue. I think you need a micro switch on both rudder pedals. If both pedals are pushed, you get a panel indication of speed brakes. Imagine leaning forward to search for a forced landing sport, and accidentally putting pressure on both pedals in an engine out glide? Secondarily, you will probably make your test pilot nervous because they can't dampen flutter with pedal pressure. Additionally you will probably need to test it at full deflection up to Vne.
Love this idea, more fighter plane style. But the idea of having fuel in direct contact with composite adhesives in the wing is a complete turnoff for me, so unless fuel bladders are installed I won’t be having anything to do with this plane no matter how innovative it is.
tropicthndr Thank you for watching! What is your objection to composites contacting fuel? The epoxy and adhesives we use in the fuel tanks are fuel compatible.
I understand the concern, although wet wings are not uncommon. Other wet wings are sealed with an adhesive sealant in GA aircraft. Nasty stuff, I’m told. Most VANS, I believe. If the materials used in DA1 are fuel compatible then where is the issue I wonder? I do recall seeing some issue with fuel containing alcohol here, but that is an issue widely held in most GA aircraft.
Perhaps the brake should have a different mechanism than the pedals, to reduce the risk-error factor and that the pedals are only for maneuvering. Not because of the pilot capabilities, but because if one of the systems fails, it does not affect the other. 2 more pounds can be used for the necessary counterweight on the tail 🤔🤓
There are two issues I think you skipped or at least did’t list :
- traditional airbrakes also reduce the wing’s lift, which greatly increases the drag
- During fast flight some low pressure occurs at the rudder’s trailing edge. Will the twin rudders be sucked, open a little and therefore increase drag ? I suppose that that’s the return spring’s job, still it may harden the rudder’s response to the action on the pedal.
All together your aircraft is very well designed and excepts too many “glued” components, you seem to have done a magnificent job ! Congrats 😊
That rudder is nothing but an outdated and obsolete tech straight from the 1930 design books. List 1 benefit of that design, and I'll write you book on its drawbacks.
Also the high speed force feedback can be tuned with winglets, that's not really an issue at all. The problem is #1 you don't need to have airbrakes on the wings, especially on a superlight, a simple flap would make the difference you need. #2 the wings DO have airbrakes with the flap design used...There are so many fundamental design errors in this airframe I can't be bothered to spend more time on it.
I admire your drive and passion to start a project like this. As an engineer who loves to innovate anywhere I can, I like your ingenuity of integrating a speed brake into the rudder. I was considering a similar idea on my plane, except as applied to the pivoting canard instead. I have some friendly advice I'm sure you don't want to hear from some random nobody on the internet, but I did notices two issues with your design that would become evident on the first round of high speed taxi testing, It is an easy fix if a little hard to explain.
1. Your split rudder design is not dynamically balanced to offset the extra control force required at your high cruising speed as the rudder deflection is increased. A balance isn't always required, but if in the future you find one necessary it can be incorporated with a dorsal horn balance at the tip of the left rudder and a ventral horn balance at the tip of the right rudder.
2, The second issue and by far the more important, is the intent to connect the left and right rudder flaps separately to the left and right rudder pedals with the speed brake function requiring constant force from the pilot on both pedals to keep the rudders open. Something which would increase pilot workload both physically and mentally during landing procedures. The fix for this is to implement a rudder control mixer device similar to a v-tail Beechcraft controlled by a distinct ratcheting speed brake lever in the cockpit. This would in effect be as simple as piece of steel C-channel with a hole on either end allowing the respective left and right rudder cable to pass through either hole. The plate will have a pivot in the center connected with a push/pull rod to the ratcheting control lever. When the control lever is pulled the plate slides down the rudder cables until it impinges on knots or clamps placed on the cables thus tensioning the portion of the cable connected to the rudder flaps, this motion will simultaneously open both rudders. The further the latching lever is pulled, the more the rudder flaps will open and thus a high amount of drag is produced. The extra control force resulting from the increased drag is taken through the mixer pivot anchor into the airframe, thus the increased control forces produced by the increase in drag are not felt by the pilot through the rudder pedals. Rudder control through the pedal remains unaffected even when the speed brake lever is pulled due to the speed brake control mixer incorporating a pivot between the two rudder cables. If the pilot adds additional input to the right rudder pedal the mixer will pivot about its center and let off a equal amount of tension/slack to the left rudder cable and vice versa. The clamps placed on the cables with be positioned such that when the speed brake lever is in the released position, the cable clamps will not impinge on the speed brake control mixer even at full rudder deflection, thus preserving independent control of either rudder flap.
Beautiful, I like your thinking.
Good luck with the split rudder, I hope it works for you right out of the box. Depending on what degree of offset you put in the thrust line and vertical stab., will determine the amount of rudder needed in take off and climb. Some of the light aircraft I've flown have required considerable rudder throughout the climb phase, and I do have some misgivings about how the extra drag of the s.r. might affect climb performance
I'm a VariEze builder/pilot and love all the innovative techniques and features you're putting in the DarkAero. I'd like to share my experience with the independent rudders on my VariEze. At high speed they are difficult to use as speed brakes because of the yaw produced by even a slightly uneven application of pedal pressure. It's pretty sensitive because of the high airspeed and takes concentration to keep the airplane tracking straight for the minute or so while the speed brake is needed. For that reason the only time I use the rudders for speed control is on final approach when I realize I'm too high. And even then I find the feature to be of limited use because of the attention it takes to control yaw while modulating the drag to get me back on glide slope, in addition to all the other things happening on short final. The extendable 'belly board' on the VariEze and Long-EZ is a lot more useful since it doesn't require attention after being extended, allowing the pilot to focus on other things. However, it can only be used at lower speeds such as in the landing pattern.
May I say thank you for the excellent series of videos about this project. I have been a commercial pilot for over 30 years, mostly jet aircraft, and speed brakes were an essential part of the flight control system. There is a saying in the jet pilot community, “you can go down or slow down, you can’t do both”. But that was high speed jet aircraft. This is a high speed low drag propeller aircraft and there in lies the difference, the prop at low power is a very effective speed brake. Can I suggest this split rudder is a solution looking for a problem. It is very cool though...
My thoughts exactly. I do think it’ll be a fine aeroplane though!
If you allow the rudder sides to move slightly past center you could trim with little drag. Handle operation of the brake and mix like a flaparon.
I was thinking the same thing, and if both rudders utilize return springs they should follow each other tightly
Exactly. For a design supposed to be operated at top speed, as is this is a feature that would actively prevent it from ever reaching said speed stably.
@@meusana3681 Some really questionable design choices with this aircraft. Every time I watch one of these videos it's like they're trying to do everything opposite of what the fastest and most efficient aircraft are utilizing. No winglets, split rudders, split flaps...I just don't know what to think of these guys. About the only aspect I see that could make this aircraft perform is the fact that it might end up being really lightweight due to all the things it lacks.
Yup. It's oceangate all over again. Some really shoddy and outdated engineering coupled with new age materials and suddenly everyone is raving that this is "new tech" for some reason. For this reason, I don't think much of them. And I bet they have heard this argument from internal engineers too, just didn't want to listen.
Split flaps and split rudders were tested and became obsolete in the 1930s (basically only USSR used split flaps in WW2, and no one did split rudder even thought the tech was heavily tested). Why are they even pretending they're doing something new here? @@Skinflaps_Meatslapper It's basically a superlight with out of the box controls...Almost like they focused on the "how" for so long they forgot about the "why".
Also the exact thing that's supposed to make this aircraft good is the same thing that will make it suck. Light airframes hate drag, any amount of sideslip is gonna tank its efficiency and speed. Apply rudder and it's like a car driving into sand.
I really like the idea of a split rudder.
That speed brake functionality is probably going to be important for such a low drag aircraft design.
optimizing a high speed aircraft, yet one of your primary control surfaces can't help but be a speedbrake under normal conditions. Every time you're not in absolute neutral position, you have deployed the airbrake to an extent.
I have an idea that may work.. maybe incorporate magnets to keep the split rudder closed, so in cruise where minor rudder is required, it acts like a conventional rudder. If you push both pedals, then it’ll overcome the magnetic hold, split and give you air brake function.
Good idea
If the opposite hinge allowed the non deflected rudder to do that, the suction from the vortices would pull it back with it anyway, no need for magnets.
Was thinking the same thing when l read your comment.
How about electromagnets so they are easier to disengadge..... you are already fighting both aerodynamic and spring pressure...the weight could be an issue. This design as presented looks a little vulnerable to flutter in my eyes... there are no balancing horns or surfaces.
Permanent magnets would make the action "sticky" - that would be very undesirable. Electromagnets would add complication and dependence on power supply, which would also be very undesirable.
I was introduced to this aircraft by Michael MD (thanks bro) ... been following Scrappy, Raptor and now DarkAero.
Oh yes... I am from India and love flying stuff. Was a Microlight Trike flyer for over two decades. (just saying)
Hello DarkAero!
Cheers
Neville, thank you for the comment and thank you for following our journey!
@@DarkAeroInc TOTALLY MY SELFISH PLEASURE. CHEERS ...and infinite happy landings
The DarkAero gear is similar in gear extension geometry to the SX-300 landing gear in that it slants forward from fuselage to wheels. But the DarkAero's gear is less complex. Nicely done guys!!
This is an awesome project and great video record of it. Also gives us all something cool to watch in between Mike Patey's videos!!!
I like that the split rudder does not disrupt the main lifting surface, and leaves more wing volume available for fuel or whatever.
Disrupting airflow over the wing is one of the reasons a wing mounted airbrake works well as an airbrake. By spoiling lift, the aircraft needs to create more lift via AOA, thereby increasing induced drag, so it's a twofold effect. The amount of fuel you save by not adding airbrakes to the wing probably amounts to a gallon total.
Saying vari-EZ's have split rudders so yours will be OK is just not correct. The split rudders on those canards are designed to create drag force far away from the CG to create a yawing force. Your split rudders will create more drag than they do lift, just like split flaps. You want a rudder in a conventional layout to make a lifting force to create a yawing moment. Creating a lot of drag won't work and rudders are critical Additionally, comparing to the shuttle, whose rudder functioned normally but could split in half for air brake functionality is also a bad comparison. Good luck. Sometimes being different is just a waste of time.
I'm loving the vlog style videos. Keep up the good work!
Marty G thanks for watching!
I like your guy's analytical approach from design to fabrication, and of course, including the cool factor, I mean, that's what flying is right?
However, you've overlooked stating what I believe are the the two most critical factors when comparing the split rudder type to the fence type.....
No additional control to have to remember where it is, how to use it and then also remember to stow it (gear up landings come to mind...). Frankly, when you think about it, it's natural instinct to stomp the rudder pedals for braking, right?
Now, most importantly, you've eliminated the possibility of an asymmetric drag and lift spoilage condition if only one fence were to deploy due to a mechanical failure.....How would that literally end up?
Brilliant guy's! Keep up the great work!
2 questions:
1. Does it effect rudder authority?
2. Does it factor in slipstream around the tail by using a cam of some sorts?
"It's desirable to be able to control the thing..."
Love following your progress. I hope the spring mechanism is well tested and bulletproof. It seems a failure in this mechanism would lead to catastrophic flutter.
What about controllability and spin recovery? In the canards, the rudders are at an extreme lateral position, therefore differential drag is sufficient for yaw control.
Excellent, glad too here that it is a mechanical system and not electric!
Guys I am a big fan
Man..... What a awesome plane you have made.
range and speed great
Just make it reliable as a toyata
Great video, I have experimented with split rudders on RC aircraft and another big advantage is they don’t flow turbulence on to the elevator / rudder like inner wing or fuselage mounted ones do.
I can’t believe I didn’t know about the staggering split rudder!
ash smitty apparently it was only implemented on the first one.
DarkAero, Inc Cheers, I wonder why they dropped it.
This very well might be my next build. Besides being composite with a retract, this split rudder idea I find the most appealing. I'm guessing you'll be adding a bit more structural reinforcement than what you displayed.
Also any thought of adding trim without inducing drag? It would have to be able to move past center while closed.
Justin Wylie we will probably initially fly the prototype without rudder trim but there are a couple options we are considering. One would be a fixed position ground adjustable trim tab. Another option would be an in-cockpit adjustable spring tension system that applies a light tension to the rudder system to give a small rudder deflection. There are commercially available trim systems like the latter option available for Vans kit aircraft.
@@DarkAeroInc Both options would probably work. I have Aerosport's tension spring system on my 10. The only issue I see on a system like that on a split tail would be that compensating either way would induce drag.
@@_Stark That is also an issue with deflecting a conventional control surface to trim. At small deflection angles (trimming) the drag increment is very similar between both style of control surfaces.
@@_Stark How do you like the Aerosport system? That's the unit I was referring to.
@@DarkAeroInc It works, but I also have a yaw damper so I only really use it in extended climbs. The only downside is being 100% mechanical there's no trim guage.
Great presentation. Aesthetically, I do find the DA1 rudder pleasing. Speed brake use is often periodic in use, so an atypically designed deployment may have less operator consideration than say, a wing flap or a flying control surface.
Practically speaking then, does the split rudder speed brake involve the pilot simultaneously depressing both rudder pedals? I suspect the pilot learning curve will be steepest in operating the speed brake and commanding yaw at the same time. I’m thinking of left yaw in a descent with speed brake.
Actually, this leads me to the questions of engine mount cant and tilt and rudder offset. Does DA1 have one or both? How much yaw will be induced by power on pitch over?
Not a pilot, but I'm just wondering if there are situations where you need to have reasonable rudder authority while the speed brake is on ... And if so, will this design be ok?
That's an easy problem, just don't fully deflect the rudder surfaces when used as a speed brake. This will allow one side to increase deflection and the other side to reduce deflection, creating an imbalance, similar to the way mixed control surfaces work. They did the same thing on the shuttle. I don't see this being a great design to live with on a daily basis though, as there will only be one speed in which rudder correction won't be necessary, and even then you'll still need occasional nudges to keep it tracking straight. All other speeds will require some degree of deflection, meaning the rudder will always be a speed brake to some degree except at that one speed and throttle setting. Even the shuttle rudder operated like a normal rudder with both halves following each other until they needed a speed brake, and only then did they split. I have a feeling that after some flight testing, they're going to redesign the split rudders to follow each other for at least the first third of their deflection before splitting. That should cover most of the envelope in a normal flight regime so they're not constantly paying a drag penalty for being cute.
This is interesting but the control method seems like it would be cumbersome. A separate speed brake handle and mixing box to still allow rudder input with the speed brake deployed would be best IMO. Another thought to eliminate the drag when it's not needed, is to have the split rudders mounted in a carriage of sorts that's then controlled as a single control surface, so the rudders only split when the drag is needed.
A few questions - how will the prop slipstream interact with the split rudder design? From other videos I gather you have pitch and roll trim but don’t have rudder trim. You may or may not need rudder trim to counteract slipstream, but I’m guessing with a powerful engine on a very light airframe, you will. If you do, won’t a split rudder translate into an effectively “always on” speedbrake? Is there an airspeed limit for speedbrake deployment and if so how is that implemented? What happens if aerodynamic forces overcome the spring return-to-center on the rudder?
A big disadvantage seems to be that pilots might by accident apply speed break while actuating the rudder. Say you are in a difficult crosswind approach and have to change the rudder position all the time. This includes the rudder crossing the neutral position. Neutral crossing with the split rudder system requires that the pilot lets go of one rudder and than pressing the other one at this moment. If the timing is off or the pilot keeps some pressure on one of the rudder paddles, he will actuate the speed break - by accident.
On a normal rudder the mechanism fundamentally only has one degree of freedom so this much more intuitive. To me if feels like if you want make this work this sh
The cost does not seem like a good argument to me either because you can simply, make the break yourself out of carbon fiber as you do with the rest of the aircraft.
That’s an elegant design solution. She’ll fly, I’m certain.
Did you consider a standard rudder function with gears to perform the split for speed brakes? The rudder halves could pivot left or right as one until for yaw control and trim without inducing excess drag and the split speed brake function could be controlled with a pull handle like a parking brake The speed brake would then be independent of pedal movement and the gears would ensure equal application. two 1/3 arc meshed gears should be sufficient for speed brake deployment and springs on the hinges would force the shells together on the ground and aerodynamic forces would aid that function in the air. Speed brake are a once a flight use item, so it should be better to not compromise rudder overall drag for the rest of the flight regime to provide that function.
Innovative concepts and ideas.
This all makes sense. Do you have a similar explanation of the choice of split flaps?
Great video and thanks for sharing! Why only use the vertical stabilizer as a spoiler? Why not also include the elevators?
Adding it to the elevators would probably get a bit dicey mixing it in with pitch control. The split rudder was mechanically really easy to implement and we had a little bit of a foundation to work off of looking at other similar implementations like the ones we mentioned in the video.
Complexity is it's own monster....
How susceptible would that design be to gust damage while parked, and , would you need to employ a gust lock whenever parked or possibly an internal locking bellcrank?
Out of curiosity, under reduction of parts principle, did y’all consider a V tail? and if so, is it possible to do both as a split rudder in that style? I bet there are some different lever arm considerations to apply similar self induced drag purposes, but in general, same applications are available in less parts no?
That Hondajet has massive attachment fittings for the speed brakes.
Have you considered adjustment on the centre stop to enable trim on the rudder, should be simple-ish could be light weight and improve performance by lowering drag
I like your commentary on why it's lighter, but for PPL, how often do we have to use a speedbrake? The traditional rudder is on a pulley system, so the left and right rudder pedals are mechanically linked, while for your split rudder, it's not and we have to consciously lift one foot and press the other.
However, I think it's interesting that this creates both a risk and a redundancy. With two rudder linkages, there's twice the opportunity that one of them will break. However, if one breaks, you're not left fully without yaw authority as you can use the other one. If the left rudder breaks, for example, then you can still fly by only making right turns using the still-functioning right rudder.
Good Point Alan. I wanted to add that I am not a big fan of both the split rudder and split flap system. Maybe the guys at Dark Aero can answer this question.
When using the rudder, there is going to be a lot of drag and I would assume some buffeting associated with that. Just because the airplane is designed for high speed cruise flight, doesn't mean that pilots don't want to have fun and fly some maneuvers around clouds, formation flight, etc. And I personally, would think the feel of the rudder pedals would feel odd when pressing on the left pedal and the right one does not move backwards in sync with the left pedal. I would also think it would be easy to inadvertently split the rudders and act as a speed brake in normal flight because the rudder pedals are basically your foot rest.
For the split flaps. I have not seen that in any airplane since the 1940's or 1950s. I would have like to have seen a Fowler style flap to increase the wing area and lower the stall speed. I'm sure Dark Aero had a good reason for going with the split flaps. Also, looking back at some of the designs from WW2, notice they have holes in the flaps / dive brakes. These holes were an afterthought to solve the problem of buffeting when deployed.
@@TheKaptainkraig Haven't heard them once talk about split flaps. Don't know where you got that from.
@@kvnkaveman The split flaps are clearly shown in at least one other video, but it may have been released since your comment.
I can’t wait to see her in the air!
Mowdown thanks you! We are excited to get her flying!
How do you 'tune' the split rudder on installation and during initial flight test so that the aircraft flies 'straight' ?
Do you have to rely on trim and if so, how is that accomplished, manually or electromechanically ?
The main disadvantage of this system is in my opinion that when your rudder is off center, you also have the speedbrake partially deployed, regardless whether you want it or not. But I'm not a pilot so I don't know how much of a disadvantage it means.
As a pilot, I can assure you that your thinking is correct.
Noice but wb failure rates, complexity and stuff?
I'd make the split rudder an option to come later once everything else has been figured out and you have actually concluded that the usual means (draggy landing gear, flaps, prop in flat pitch) are not slowing you down enough. I'd just put the expensive speed brakes into the prototype and be done with that issue and see whether I actually need them.
It’s smoother than other aircraft that use speed brakes. I’m sure they have already worked it out.
You could say the same thing about any of the other features. How many full-scale flying prototypes would you want to build?
Points, taken. Slippery airframes like this need a brake when in flight in a descent well outside the terminal control area where gear and flap settings would not be changed. For instance, the normal operation of gear and prop pitch in most retractable gear aircraft is usually, not until at or near the final approach fix. Roughly
@@user-tv5dt3nm9y I thought this to be the inherent problem of big engines with a limited cool-down gradient and pressurized airplanes. Those cannot significantly reduce the power on descent, else they would cool down too quickly, especially at high altitudes or not produce enough bleed air for pressurization. Turbo charged engines also need a minimum manifold pressure to keep running at very high altitudes. I would think that this plane allows cutting the power on descent.
Martin Renschler well there’s a lot to unpack in your statements. As far as the DA1 is concerned, I believe the concern is of how to go down and slow down in a time and space limited airspace. There are speed limits to consider, Vne, and maneuvering considerations like turn radius and bank angles, blending with other traffic, accelerated stall margins, and uncomfortable g-loads with a higher loaded wing. Lol, your significant other may not find 60-70 degree bank angles at 2-2.5 g as much fun as you do. I’m not going to touch the shock cooling mythology.
Just how slippery is it? Look at the DA1’s cruise airspeed projections vs HP, its overall dimensions, the wing loading, and a clean, non-parasitic drag producing skin. To get your head around it, compare those numbers with aircraft of similar design goals out there.
A sliding stop plate that is wedged to or from the center that moves the sides simultaneously keeping them tight to each other for trim
The free-cantering nosewheel means that the rudder and differential braking are the only means of directional control after landing.
I have the same question as others relating to how differential toe braking will work without the using the opposite foot for leverage.
I also question how easy it will be for pilots to transition to non-linked rudder pedals. Not easy to remember to lift one leg while pushing down with the other.
Thanks, great project, but what about trimming? If either half rudder cannot go beyond central how do you trim?
We will probably initially fly the prototype without rudder trim but there are a couple options we are considering. One would be a fixed position ground adjustable trim tab. Another option would be an in-cockpit adjustable spring tension system that applies a light tension to the rudder system to give a small rudder deflection. There are commercially available trim systems like the latter option available for Vans kit aircraft.
I must have missed the part where you discussed the flutter issue. How are you mitigating flutter and how are you controlling the sidestick forces for the pilot?
Another point: most pilots fly with their feet resting on the rudder pedals, usually with a light constant pressure. Unless you build in in some considerable breakout force, you'll be flying with a drag brake the whole time. And if you have a bit in breakout force, I bet the feel when flying will be horrible. Just my thoughts.
Are the pedals completely independent (leading to this problem), or are they mechanically linked (so they they will not both deflect at the same time)?
Definitely cool, simply because you are saving weight and minimizing aircraft parts.
Agreed 👍
There has always been the search for a better mouse trap. So go for it guys! Looking forward to the proving when it flys.
How do you do toe brakes with this type of setup? I think that would drive me nuts if it was a separate lever or something
Hey guys, that split rudder idea, while cool at first sight, may backfire at you - be careful. Split rudder system in shuttle, B2 and other military planes is carefully controlled by software, sensors and activated by precise machinery only in specific flight regimes. Your system is manually actuated and easily can be mismanaged in flight, and as someone using it in VariEZ mentioned, puts more workload on a pilot. Please consider removing or offer it as an option. And if you offer normal rudder with trim control - you will have my deposit to get in line for your kit!
I agree with you... Especially on their very first aircraft, they should be taking it easy with the "special" features, and maybe leave that for the 1.2 version of the plane instead. What initially matters is that the plane flies safely and predictably - flaps should do the trick for slowing down on approach. A complicated rudder system such as this will only bring delays. If the FAA has to approve any of this, I can only see it adding more time for certification.
Is the split rudder safe under icing conditions?
This isn't supposed to fly in icing anyway.
But with most symmetric tail surfaces, icing doesn't affect it's ability to provide balancing and stability forces. Some airliners don't even use anti ice devices on the tail surfaces.
What about spin recoveries? Wont the split reduce the lift the rudder can generate to counter a spin? I suppose drag back there could help but i suspect youll have fair amount of spin testing to do. Very cool though.
I agree with your thinking. In addition, the vertical stabilizer also has a fairly aggressive airfoil leading edge, along with an unusually high aspect ratio. This means there is a possibility the vertical stabilizer will stall at relatively small angles of sideslip, reducing lateral control even more. Most vertical tails have an AR of less than 2. Not~>3. This design will have more effectiveness at small angles, though, due to it having an improved lift curve slope due to higher aspect ratio.
won't this have more drag during high "p-factor" operations which require rudder? Extra drag while rotating for take off or fighting a x-wind doesn't sound fun. If it operated like a normal rudder AND had the split function that would be ideal.
sounds sketchy in a low speed crabbing situation where you want to bleed as little speed as possible while yawing the nose off. If you've got reserve altitude you're probably fine since your tail inputs will always bring the aerodynamic centre backwards.
I do really like it as an airbrake design though.
Canard aircraft (i.e. Rutan inspired; e.g. VariEze, LongEZ, Velocity, Cozy) have the same setup and they simply avoid using much, if any, rudder input in such scenarios. Some of the big jumbo jets also indicate a preference for landing crabbed as opposed to attempting a low-altitude sideslip, and IIRC at least one of the POHs or airline manuals prohibits sideslip landings.
Sideload on the gear isn't as much of a concern when you're touching down at ~1,500lbs.
@@ParadigmUnkn0wn the canards just have single direction actuation not exactly the same thing. And landings are not high pfactor scenarios. Jets don't even experience pfactor...
I love KIT cars and KIT aircrafts. Knight Industries Twothousand ftw!
Horizontal Stiffeners on individual rudder splits might give more Stiffeness for better surface controls by avoiding more deflection of skin alone..
i.e. Normal rudder edge on inner sides- without affecting interfaying control mechanisms..
How are you going to do rudder trim?
We will probably initially fly the prototype without rudder trim but there are a couple options we are considering. One would be a fixed position ground adjustable trim tab. Another option would be an in-cockpit adjustable spring tension system that applies a light tension to the rudder system to give a small rudder deflection. There are commercially available trim systems like the latter option available for Vans kit aircraft.
You guys are awesome...NASA and SpaceX might get us to other planets...but all those astronauts and engineers are gonna buy one of your planes to get to work!!!....
@@DarkAeroInc Do you have plans to allow for a yaw damper? I'm wondering if this might be helpful for creature comfort given how short the aircraft is!
Have you addressed a 'Yaw damper' system? That seems almost required for long distance high speed cruise? JMHO --gary
This is awesome. Take my money 💰
Are you also going to split the elevator?
Did you guys make any mold fiber lay up vids for fuselage and or wings?
We haven't made any video yet on our mold making process but we were just talking recently about how we think it would be beneficial to show folks what kind of work we put into for our molds and mold patterns.
THANK YOU MAN KEEP UP .
super cool.
Doesn't the split rudder create drag over and above a regular rudder anytime that it is used? That would be bad if you are in a near stall situation on landing and want to use your rudder? What am I missing?
CG => Pitch issues?
Speed breaks are generally mounted close to the CG. By exerting a breaking force so far aft and above the CG are you not going to create a pitch moment potentially leading to a stall if not corrected with aileron input?
Further, in the event of an asymmetric input (meaning you extend one more than the other) are you not going to create yaw + pitch up, potentially leading to a spin?
you guys are amazing
Where does the funding come from? We've been looking at the same thing for THREE YEARS NOW, yet no flight.
Nice idea but I believe your engineering is not completely thought through to the pilot work load. I think you need to implement a separate control for the speed brake function that deflect both rudder halves equally while leaving differential rudder input in the pedals. I.E. flaperons. It should be simple enough to connect a control to the bell crank to deflect each rudder surface equally for the speed brake.
I love y’all and what you do
Thank you 😊
This reminds me of how the Long-EZ rudders are set up.
3 minutes in now and there's the Long-EZ.
I'm also pretty sure that the deflection of the air flow at this place of your plane will give it a super good position for landing 👌
Im wondering, with a split dudder will it have an effect on spin recovery!
The A-6 Intruder used a similar function at the tips of its wings. I don't know if they could be individually deployed to provide directional control assist.
Sir / madam ,there is no internship in the website
There isn't one yet! But don't hesitate to send us a resume at info@darkaero.com.. As we ramp up into production, we will be on the search for full time employees.
Have you tested this on an actual plane yet?
I think you'll have less rudder authority with only one side moving past center for yaw control.
And you don't have aerodynamic balancing, so the control input forces have to be greater.
Hi guys! I’m not sure this is really related but: how does this split rudder works in case of a spin? Did you have the chance to simulate the spin tendency of DA1?
I get the feeling that these are the kind of designers that slap a BRS on it and say it's not rated for spins.
How many pilots would want a plane that could kill their passenger/s and themselves from not being responsive in overcoming even an incipient spin? Where is the efficiency in hauling a plane recovery chute system?
Control surfaces on high speed aircraft are balanced to prevent flutter. I don't see any area ahead of the hinge point to add counterbalance weight. Be careful on those first fast flights.
He mentions that in the comparison.
How well will the rudder speed brake work in a spin.
Interesting, didn't know that hondajet had a baboon brake. Not sure that's elegant engineering. But it makes me wonder, could tab style airbrakes on the wings work effectively as a rudder if placed far out on the wings? I hunch that it would express too much as drag but if the wings have a certain length, would it be... if you could forego a moving rudder, that would be elegant. If you take care of stability and trim with a static tail then it would only be for approach maneuvers where any slight inefficiency is worth the elegance.
Also I wonder, indeed assume, that rather than a prominent vertical tail, it would be better to reach far back with a much smaller tail fin like a shark does. Even though a shark uses it for propulsion. If a little extra length on a skinny tail makes a much better plane then it can be worth ignoring the hangar demands.
If you need rudder in cruise, won’t this slow you down like crazy?
when darkaero is climbing, and pilot is on the left ruder to fly straight, how much drag will it add to the climb? i do love the idea.
Good question Steven! At small deflection angles like trimming for climb, the drag increment of the split rudder is similar to a conventional rudder.
How does this affect airspeed in critical slow speed produces such as landing in a cross wind or side slipping.
Does the increase drag affect take off performance in a cross wind.
Is there a reduce limit to allowed cross wind component when landing.
Wouldn’t you create a lot of drag when just using the split rudder as a rudder since the air can’t flow around the control surface? It would render the rudder less effective due to the air turbulence on the low pressure side?
There should be a 3D printing of this as a smaller model, so that it could also be flown as a RC plane.
It looks like you are using Aluminum hinges and rivets. Aluminum and carbon fiber can develop severe galvanic corrosion when in physical contact in the same component or structure.
This split rudder, it makes me think of less drag turbulence behind the rudder.
Its neat man
If it turns out not satisfactory have the Coolest Air-brake as yet, F15!
Why not make the stabilizer skin bend at the line where the rudder starts instead of cutting it and using hinges? Couldn’t that be done by having right amount of right kind of carbon at the hinge line?
@darkaero , will you guys show the engine mount drop test?
We recently finished construction of our engine mount/nose gear drop test rig. We will likely share some of that testing.
Why are there not any fillets, winglets or other speed increasing tricks on this plane?
Galvanic corrosion is prevented between the split rudder Carbon surface the rivets and the alum hinge How ?
When is this thing going to fly?
One suggestion. Make the wing tips easily replaceable. By testing various tip configurations you could gain 12+% efficiency. Of course only after you prove the rest. I Love your project and videos.
Does deploying the split brake effect pitch because it's the full length of the vertical stabilizer? It's hard to see from the video if it's wider at the bottom or not.
Thien Lieu a minor pitch change is possible when the speed brake is deployed since the drag center of the two rudders sits above the aircraft CG. This isn’t much of an issue though since pitch changes also result from extending flaps or landing gear or even entering a banked turn.
@@DarkAeroInc not the same flaps and gear are deployed with altitude air brakes may be deployed close to the ground in the flare would result in a hard landing or nose wheel collapse or worse
If the normal speed brakes had one for each wing, wouldn’t that equal 18 pounds at 9 pounds each, giving you a difference of 17.5 pound savings?
How do you isolate the dissimilar metal and carbon fiber on your hinges to prevent corrosion?
Loyd, thank you for watching and for the question. Galvanic corrosion is something we get asked about often. This is probably a good one to update our FAQ page with. In general, any of the aluminum present on the aircraft is electrically isolated from the carbon fiber. All the rivets used in the aircraft are stainless steel.
I think there is another human factors issue.
I think you need a micro switch on both rudder pedals. If both pedals are pushed, you get a panel indication of speed brakes.
Imagine leaning forward to search for a forced landing sport, and accidentally putting pressure on both pedals in an engine out glide?
Secondarily, you will probably make your test pilot nervous because they can't dampen flutter with pedal pressure.
Additionally you will probably need to test it at full deflection up to Vne.
Love this idea, more fighter plane style. But the idea of having fuel in direct contact with composite adhesives in the wing is a complete turnoff for me, so unless fuel bladders are installed I won’t be having anything to do with this plane no matter how innovative it is.
tropicthndr Thank you for watching! What is your objection to composites contacting fuel? The epoxy and adhesives we use in the fuel tanks are fuel compatible.
I understand the concern, although wet wings are not uncommon. Other wet wings are sealed with an adhesive sealant in GA aircraft. Nasty stuff, I’m told. Most VANS, I believe. If the materials used in DA1 are fuel compatible then where is the issue I wonder? I do recall seeing some issue with fuel containing alcohol here, but that is an issue widely held in most GA aircraft.
Perhaps the brake should have a different mechanism than the pedals, to reduce the risk-error factor and that the pedals are only for maneuvering. Not because of the pilot capabilities, but because if one of the systems fails, it does not affect the other. 2 more pounds can be used for the necessary counterweight on the tail 🤔🤓