Canard Aircraft Aerodynamics - Introduction

[@chrischain_]

Thanks for posting this. Really amazing to get some of your wealth of knowledge on these topics.

[@dwaynemcallister7231]

Interesting discussion, I own a Europa monowheel which was the idea of Ivan Shaw who had worked with Burt Rutan long ago. Although the Europa design was really a team effort with the wing airfoil, tail, control surfaces designed by Don Dykins the Airbus team leader who designed the Airbus wing. The structural engineering was by Barry Mellors from Slingsby. Many of the first Europa builders had also built Long eze types first including Ivan who built a twin engine Longe ez. So the Europa was designed because the Long eze was not so great on soft grass airfields common in the UK.

[@saromarcarian4709]

Great presentation, Marc.

[@13634landing]

Thank you Marc for posting this on your channel. Great information!

[@Sectzi_Sw3AtEr]

I’m building a foam plane for my aviation class. I’m modeling my plane after the Eurofighter. What airfoil do you suggest I should use for my wings and canard? I’m new to this stuff so I don’t fully understand everything in the video.

[@zeitlinm]

Can't help you with airfoil recommendations, particularly for small, low Reynolds # model planes. You'd have a lot more luck discussing this with folks on some model aircraft forum. Good luck.

[@shadok233]

Hi Marc, so did you ever got data from that wide-body Cozy MkIV? Also, has anyone tried staggered seating other than the StaggerEZ? Seems like an obvious solution at first glance.

[@zeitlinm]

Nope. Peeling actual testing data out of most E-AB aircraft owners is the worst form of pulling teeth. Most do not do enough or the right testing, and don't collect data correctly. And yes - there are a few aircraft with staggered seating. One in Switzerland and a COZY MKIV in Texas, that I know of.

[@shadok233]

​@@zeitlinm Too bad, but I guess that won't change unless FAA makes the task-based flight testing regime mandatory.

[@zeitlinm]

@@shadok233 You think that just because something is mandatory that people will do it? Without an enforcement mechanism, nothing will change. People just do not understand how to test, or the value of it.

[@shadok233]

@@zeitlinm True. In Switzerland, it is mandatory to conduct flight testing and you have to complete a flight test course at their EAA-equivalent before first flight, but I guess that's not really an option for the US. Just a bit of a waste to see so many people experimenting with their experimentals without ever publishing results (many do, I am aware). And then someday, the thing lands on Barnstormers being described as the bee's knees even though it handles more like a bumblebee's bum.

[@km4lkx497]

Great info here. Are there other discussions of this caliber?

[@Triple_J.1]

You might be interest in checking out Mike Arnolds thoughts on drag reduction. kzbin.info/www/bejne/qKnZoHeYj9Wij5o

[@princetonleger8256]

Thank you!!!

[@mytech6779]

I imagine that it may be difficult to optimize(I don't know how senative it would be to variable flight conditions), but it would seem that adding twist to the main wing would at mitigate much of the effect of the downwash from the horizontal stabilizer. Such that the effective AoA remains constant over the span.

[@xpeterson]

I was under the impression that wingsweep was also to keep the horizontal center of aerodynamic pressure behind the CG. Is this an accurate assessment? And if not, why are the wings on the Velocity Twin still swept despite exchanging the wingtip vertical stabs for a single central one?

[@zeitlinm]

You're correct - the AC needs to stay in the same place, whether the winglets are on the tips of the main wing or not. Moving the winglets doesn't change that need. However, the original design (of the VE or LE) from which the Velocity sprung had swept wings to put the winglets aft of the CG, and once THAT design was set, it would have taken a very large redesign by Velocity to straighten the wings, and there was no reason to do it. IMO.

[@ericstephens4413]

Are your slides available as references? Excellent material! It's really helped me get ready for an EAA breakfast talk around canards. My focus is a more history and less aerodynamics.

[@zeitlinm]

cozybuilders.org/Oshkosh_Presentations

[@David-if2jz]

What is the point of putting the audience pic over the slides?

[@zeitlinm]

This was recorded by an EAA chapter, to which I was giving the presentation over Zoom. I didn't do the recording - they just gave it to me to post. Certainly could have been a bit nicer, aesthetically, but the content is the same :-).

[@davidbevington6064]

Why do all aircraft have vertical stabilizers but all birds fly beautifully without vertical stabilizers? Getting rid of vertical stabilizers would save weight and cost and make aircraft more efficient. I understand that is to do with roll in aircraft inducing adverse yaw which has to be counteracted by vertical stabilizers. But there are videos on you tube of model aircraft designs without vertical stabilizers which have been flown successfully and are stable, So my question is why haven't these successful tailless model model aircraft designs been scaled up to full size aircraft?

[@zeitlinm]

They have. Look at any "Flying Wing" aircraft - B-2, B-21, YB-49, etc. See: www.afmc.af.mil/News/Article-Display/Article/2737915/a-look-back-atnorthrop-flying-wings-part-1/ for a history of some. In order for an aircraft without vertical stabilizers to be stable in yaw, they either need equivalent wingtip drag devices to create yawing moments, and need active stabilization, that can require substantial computer control. Birds can do it because they have an amazing computer inside their head that can control each feather on each wing and each tail feather independently to ensure yaw stability. It's a lot easier, particularly for small, GA aircraft that don't have fly by wire control and expensive, redundant computers driving the flight controls, to just add a vertical stabilizer and take the small weight/drag hit. And it is small.

[@russellesimonetta9071]

Japanese Shinden fighter was a cool looking canard plane. The Baka ( crazy) kamikaze plane was a canard.

[@zeitlinm]

The official name of the American nicknamed Baka (which means "fool" or "idiot" in Japanese) was a conventional configuration twin-tail aircraft which can be seen here: en.wikipedia.org/wiki/Yokosuka_MXY-7_Ohka

[@frank7911]

special thanks to the participants with video, making this presentation a kind of documentation of the common sense deficit in the use of online meetings.

[@yoginero]

The conventional way is to avoid deep stalls. An unconventional way to become safer is to practice deep stalls. Spin in one direction. Spin in the other direction. Spin and change spin direction mid deep stall. Make good use every control surface available including flaps, fuel distribution, just everything..

[@bravocharlie639]

The point of the presentation however is; Careful design of Canard (actually; any) Aircraft because Deep Stalls in a Canard are fatal. The lifting surfaces that entered the Deep Stall become stable again, in the Stall.

[@zeitlinm]

Practicing Deep Stalls in canard aircraft (which can only occur if one has the CG aft of the aft limit) is a good way to destroy one's aircraft, as it is extremely difficult to exit the deep stall condition. It's only been done twice to my knowledge, and in both cases, took many thousands of feet of altitude loss to effect the recovery.

[@zeitlinm]

@@bravocharlie639 Deep Stalls in canard aircraft are usually NOT fatal. One fatality was caused (in a Velocity) by an inverted deep stall, and the other was caused not by the impact with the ground (or water, in this case) but by the pilot's attempt to egress the highly modified COZY MKIV aircraft (he was wearing a parachute) and being struck by the ejected canopy. In all the other instances of deep stalls, there was a range of injuries from none to broken bones and compressed discs.

[@mbian0same762]

wait a minute, are you saying that an infinite wing span will have ZERO induced drag? Are you attributing induced drag solely on the wing tip vertices? That's wrong my man. Any lift generated will cause a downwash of air, everywhere at the trailing edge of the wing.

[@Triple_J.1]

No, it won't. Ref: Every single complete work or textbook on the subject. Also Note: Wind tunnel results have zero induced drag. (Though the numbers must be corrected for interference drag or tunnel-wall effect). Please use the induced drag formula to check for yourself: (Lift Coefficient: Multiplied by Itself). Divided by: (Aspect Ratio: Multiplied By 3.14159265) For lift coefficient you can use: Angle of attack, Multiplied by 0.11. And then Use an Infinite number for aspect ratio. (Because we are trying to compute induced drag for an infinite span, therefore we need to know the result for an infinite aspect ratio). Its interesting to note, that a wing having an infinite span and a chord of 5ft is a larger infinity, in wing area, than a wing of infinite span having a chord of 2ft. And also note that the 5ft chord wing of infinite span may have a lower aspect ratio than the narrower chord wing of equal infinite span. How can there be a larger infinity than an infinity? I don't know, but it might be the same reason that a lift coefficient of (0.00^2)/(pi*AR*e) equals incalculable amounts of induced drag, no matter the aspect ratio and no matter how short the span. And every aircraft is caplable of zero induced drag by flying a simple parabolic flight path at a lift coefficient of 0.00, either by reducing angle of attack to zero lift angle, or by simply parking on the tarmac and going home. Also note an infinite span would extend through outer space where there is no atmosphere, thus deflecting zero air at the trailing edge, generating zero lift and therefore zero induced drag. So this theoretical nonsense actually makes sense in reality too. Apple Siri has a great explanation if you ask her what zero divided by anything else is also.

[@mbian0same762]

@@Triple_J.1 thanks for the write up, but too long to read, and not clear about your point. All I want to know is, "is tip vortex the cause of induced drag or is it just a worsening factor". OR, just to dumb it down, if you stick a wood board, with none of that air-foil shape, out of the car and feels a lift, don't you feel induced drag at the same time? I don't trust any math equation in this case. I am bad at math yes. Also what does the equation calculate? You see those 2nd order differential equations that are ubiquious in nature, after all the trouble solving it, the solution is one value at one spatial point. For a macro phenomena that is lift, with complex geometry involved, I don't believe any equation can do the whole wing and gave me a meaningful number.

[@zeitlinm]

Yeah, Justin is correct, and your position is incorrect. The wingtip vortices are not the CAUSE of the induced drag - they're the indication of induced drag caused by a finite wing having the high pressure air spill out over the tip. You have to remember that in subsonic flow, there's an upwash ahead of the wing that's equal to the downwash behind the wing. If the wing is infinitely long, this drag cannot occur. It's why gliders have very long wings, and why, if the structure (and handling qualities) would allow, glider wings would be even longer. The longer the span, the lower the induced drag. Take that out to infinity, and the induced drag goes to zero. You don't need to do the math to see it - the logic is in the books as well. And as far as not trusting math, well, not sure what to tell you. The math is a representation of reality in this case, and has been validated thousands if not millions of times. Look at aerodynamic textbooks and read the text, if you don't want to look at the math. The answer is clear.

[@williamwalker39]

Hi, my name is William Walker and I am developing a Blade Runner style flying car. It is a very unusual vehicle and thought your group might be interested in it. I call the vehicle "Sky Chaser" and an artistic picture of it can be seen in the icon at the top left hand side of this post. Clicking on the icon will enable you to see a project presentation and flight videos. Sky Chaser looks and drives like a car, flies both vertically and horizontally, and is amphibian. It has no exposed rotors, and uses the body as a wing. It also has no unfolding wings, and flies the way it looks, just like in the Blade Runner vehicle in the movies. Sky Chaser is basically a flying wing design with twin electric motors in front and has double rudders and double elevons in back for control. It also has VTOL capability and is a Tricopter configuration, with 2 tilting front electric motors in front mounted on nacels, and another electric stationary motor in back blowing thrust though a hole in the wing behind the cockpit. The tilting motors enable vehicle to transition from VTOL to plane mode. The aircraft is also car with 4 large wheels powered by small electric motors. In addition, the vehicle is amphibian, and can navigate and takeoff and land on water, both in VTOL and in plane mode. Sky Chaser has a very short wing, but its effectiveness is increased by blowing high speed thrust over the wing and by using oversized side body panels, housing the wheels, to block airflow around the wingtips and help channel the airflow over the wing. I started the project in 2016 in San Diego, Calif, USA where I built and tested a 1/6 scale model. Then I made a CAD model and got it to fly in a flight simulator. 3 years ago I moved to Sweden and work with business partner and we have now built a full scale unmanned working prototype which flies. For more information: *SkyChaser(dot)se *Project Presentation: drive.google.com/file/d/1FAdls15OriuQ4hoD2xPwXeNQDQTKpK1t/view?usp=drive_link *evtol News article 1: evtol.news/sky-chaser-concept-design *evtol news article 2: evtol.news/sky-chaser *Simulation tests: drive.google.com/file/d/19taPDO1yERAumR8OV1IFk2n1TqNLNUkN/view?usp=drive_link *Full Scale hover test: drive.google.com/file/d/1qDl5X142uC5yt_5Xcb0GUS3h-LgD4P0V/view?usp=drive_link

[@qwertyuio266]

Thank you for sharing this. Saab was first to make a succesful canard design. en.wikipedia.org/wiki/Saab_37_Viggen Burt Rutans first design clearly gives credit to Saab. en.wikipedia.org/wiki/Rutan_VariViggen I would like to see the same analysis of modern fighter designs.

[@zeitlinm]

I'm fairly certain that the first successful controllable canard design was the Wright Flyer, in 1903 🙂

[@DumbledoreMcCracken]

No one in his right mind would: Build a canard Put winglets on a wing Put a pusher propeller behind a fuselage or wing Drill any hole in fiber structural member Make aesthetics the guiding principle of an aircraft

[@seaplaneguy1]

Lots of mistakes in this presentation. Bernoulli's equation does NOT apply to a wing. The pressure difference is a minor factor in lift. It is mass deflection, not pressure. If you look at wind tunnel data with smoke segments...dot dot dot... the stream flow high above the wing is the free stream. A NO point does a dot ACCELERATE ahead of the free stream...NEVER happens. The air on the top of the wing next to the wing is decelerated LESS than the bottom, but it is clearly decelerated. Lift is lost when flow separated and this lift loss is due to the mass not following the wing, not to pressure. The problem with canards are many. Here are a few... 1) The down wash makes the center rear wing in lower AOA than outboard. That forces the stall outboard....dumb idea. 2) The useless inner rear wing is extra drag for nothing. Say 30-40% more. 3) The stall of the canard makes for a "cliff" of lift where it drops and you nose in. This means the airplane must land 10-15 MPH faster to avoid this loss of pitch control. 70 mph + 15 = 85 mph. (85/70)^2=1.47 x more wing needed for the SAME 70 mph landing speed. 4) No flaps means 1.4 max CL vs 2+ CL with flaps. 70% of wing lift. 1.42 times more wing area needed. 5) The loss of lift in the center rear wing due to canard, coupled with no flaps, gives around 2 times more wing area needed for the SAME landing speed. JOKE. 6) canards are terrible in ice, which is key to usefulness. By the time you get a canard to work in ice it has a very high drag wing. 7) Canards cannot do post stall control which is key to power on lift technology with pitch ups to 45 degree AOA. Come in at 30 degrees glide slope, pitch up 15 degree more in post stall and land at max CL at 45 degrees AOA...that is the future...not this wimpy landing on some obsolete runway. 8) The canard main spar is right in front of the pilots face blocking view. In a crash...like John Denver... that spar takes your head off...not good. No wing spar should be in front of a person to cut them in half. Just don't do it. ..... There are many more, but clearly a canard is silly stupid from this simple back of the envelope analysis. Rutan's junk is just that...junk.

[@zeitlinm]

All I'll say to this comment is that your position on how wings work is contradicted by all aerodynamicists, and can be easily refuted by a simple search for wind tunnel smoke studies. And since the performance of canard aircraft is not dissimilar from similar high performance conventional aircraft with respect to speeds, safety and runway requirements, your position on the relative merits of canards is also easily refuted. The facts are out there if one is willing to understand them.

[@seaplaneguy1]

I have done wind tunnel tests on an original design. All smoke tests show the air above the wing does NOT accelerate relative to the free stream...Sorry, just a fact. I refuted the canard already. What more do you need? Sorry, I am a mechanical engineer and fully qualified. Nobody qalified in aerodynamics thinks Bernoulli's equation applies to a wing. Like I said, canard cultist won't listen and learn. LOL. Believe what you will. John Denver died do it. @@zeitlinm

[@voornaam3191]

Which poststamp is talking? I am out of here. Get organized!

[@numnut1516]

Idk but about half of them seem to be coighing the whole time. Everyone said they would mute but didn't.

[@johnluffman7954]

Canard aircraft is equivalent to conventional wing-tail aircraft in terms of aerodynamic efficiency. However, it has aditional advantage of stall/spin resistance. Therefore, can we still say canard aircraft is better? Btw, the airliners use conventional configuration because they need highly efficient flap systems, that will produce very large pitch down moment. For the canard aircraft, it is impossible to do this because the canard is already heavily loaded, the canard can't trim the heavy nose down moment cuased by large flaps.

[@zeitlinm]

"Better" is relative, and is completely dependent upon what you're measuring. Stall / spin resistance is "better", but soft runway capability is worse. All depends on what's important to you...