Canard vs Tail Civillian

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Allan511

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I know it’s been discussed before but I would like to approach the Canard vs Tail from a different perspective.
Some of which does apply to the military use.
For clarity all statements assume same installed power and weight of aircraft. Also initially I will focus on fixed canards with control surfaces.
As someone who flies an aircraft with a full flying tail and wings that almost sweep forward I feel my input invaluable. I of course am talking about my 1967 Cherokee 140 with the Hershey bar wing Which is 4 years younger than me.
A canard airplane is like a supermodel, sexy as hell but not practical when you get it home.
WHY? you ask. Canard lovers are calling me a heretic right now.
Canards do work and can do about as good as a conventional tailed aircraft in most situations.
The number one reason to avoid canards is simple. C of G. One to four seats is doable.
Anything more gets dicey.
About 10 or so years ago I discussed at length Canards with a pilot friend who was test flying a six place canard project being built at Camarillo airport north west of Los Angeles.
His quote “ They just can’t get the CG envelope to be adequate, that damn plane nearly killed me twice”
He quit the program and it was still borne.
A huge issue with the Starship was CG as well. They went with variable sweep canards to alleviate the problem.
When I am doing a short field landing more lift and control authority are a throttle advance away. Think blown wing and tail. Try that with your pusher canard. Canards typically require significantly more take off and landing distance. I have a friend with a Long ez and another with a cozy. Novelty is the only benefit. People say how efficient the Long EZ is, but it’s an illusion. I have been in Long Ez,s a couple of times. They are efficient because of the low wetted area. You are shoehorned in there. Think BD5. This is offest by the highly loaded canard with its non optimized angle. A canard has to stall before the main wing. Bad things happen if the Main wing stalls first. If you are looking at a Long ez make sure it has the Roncz canard. The original canard would loose lift in the rain. Very bad on short final. Also a significant factor with the side by side canards and four placers is the fineness ratio And base drag, both significantly harder to optimize than a conventional aircraft.
I have been to the Reno air races quite a few times, fineness ratio, base drag and no more than 7 degrees angle from the prevailing wind direction get the best speed and efficiency. All of which are hard with a pusher canard.
Canards don’t scale up well. The CofG just isn’t as broad as a conventional approach. Even then conventional commercial airliners transfer fuel to and from tanks in the tail planes to get CG good. Puddle jumpers 100 or so seats just get five people to move to the back of the aircraft or vice versus. The Piago Avanti 3 surface allows for a significantly smaller wing are and less trim drag. Definitely a design success if not business wise.
I work at VanNuys airport north of LA and 2 or three times a week we would have one fly in and out. Amazing.
I have seen things such as a twin Cozy, allowing for a better fineness ratio, base drag element and angles. The problem is you end up with a shitty transonic area factor which despite its name matters at almost all speeds.
Full flying canard with delta wing= bandaid for the problems of the delta wing.
I don’t know for sure but I doubt there is any significant lift contribution from the canard. It is almost certainly exclusively for control. The minute you start loading a surface for lift you degrade its ability to provide control.
Not good for a fighter.
I apologize for my next statement. I am Canadian and don’t have a dog in the hunt.
When the Europeans were designing their aircraft the USA looked to be favoring canards. They were in all the magazines and on everyone’s tongue. Misdirection. Hence you have deltas with canards.
They do the job and are in my opinion excellent aircraft.
When you crunch the numbers though comparing weight, installed power etc, they are simply different than a conventional approach, not better.
Look up what aircraft hold the efficiency and speed records for single engine piston aircraft. The majority are held by conventional designs.
Sexy as a supermodel. Longer takeoff and landing distances, typically, and Huge C of G issues.
Cherokee all the way, until I can get an F18.
 
First, Cherokee have straight wings and horizontal tail because their quarter chord (40 percent on laminar wings) have straight leading and trailing edges, parallel. Only the vertical tail fin is swept and that is purely for fashion.
Cozy and other canards with side-by-side seating suffer problems with streamlining the aft fuselage. All light pushers suffer similar problems (see Cessna 337 Skymaster). Similar to Republic RC-3 Seabee pusher flying boat, they need to taper the fuselage rapidly from 4 feet wide to zero on a short distance. This can create problems with turbulent or unstable airflow. Glass Goose needed to add vortex generators to stabilize airflow around the aft portion of its cockpit fairing.

Burt Rutan designed many of his canards specifically for ultra long distance record-setting, so naturally they are sluggish during take-off. If you want to see a STOL canard, look at Rutan's Grizzly sort-of-biplane.
If you want to see canard racers, look at the Amsoil biplane and Pond Unlimited Racers. Amsoil looked like a Rutan Quickie upgraded with a larger engine, conventional horizontal tail and vestigial inter-plane struts. Amsoil flew well, but never medaled.
OTOH the Pond Unlimited Racer was plagued with engine problems and crashed. That was the only time a client of mine has died with a parachute that I packed still un-opened. An engine failed before the Pond Racer pilot ever climbed high enough to bail out. It si also rumored that he was asphixiated by fumes when an engine failed.
Piaggio Avanti flies more like a conventional airplane. Because they wanted to route the main wing spar aft of the cabin pressure vessel, they split the main lifting wing into two parts. The large, middle wing provides most of the lift and has all the usual ailerons and flaps and conventional control surfaces. Avanti's forward canard is fixed (with no control surfaces) and only provides enough lift for balance. Next time you see an Avanti, look closely at the conventional elevators hinged from the horizontal portion of its T-tail.

OTOH the Rutan-designed Beechcraft Starship had a far more complex canard with trailing edge flaps and variable sweep. The variable sweep moves the canard center-of-lift forward to compensate for a nose-down pitching moment created when main wing trailing edge flaps are deployed for landing. Starship needs those trailing edge flaps to allow it to land on the same short runways (less than 3,000 feet ... er ... 1 kilometer) as its King Air predecessor.

Rutan copied his lifting canards from SAAB's Viggen jet fighter. Viggen used canards to balance a delta canard main wing. Both the Viggen's main wing and canard have landing flaps for the STOL performance desired by the Swedish Air Force.
Lifting canards require moving the center-of-gravity so far forward that it is near the leading edge of the main wing. Look at the blet buckle of the rear seat passenger in a Rutan Long Eze for an approximation of its C. of G. Placing the second occupant's seat near the C. of G. is standard practice on light 2-seaters as it minimizes balance changes when you add or delete the second occupant. This forward C. of G. aids with pitch stability ... a trait lacking in most earlier canard designs (see Curtiss Ascender and Japanese Shinden).
SAAB Viggen was the first truly successful canard airplane, but its canard configuration has been copied by several alter fighter jets (Dassault Rafale, Eurofighter, SAAB Grippen, etc.) because fighter designers want airplanes that are naturally unstable, so they can turn quicker. They are unstable because their C. of G.s are too far aft, which is great for cruise efficiency and maneuverability, but exhausting for human pilots to fly. Fortunately jet fighter "relaxed stability" is backed by 3 or 4 channel auto-pilots that automatically stabilize the airplane in cruise. Eurofighter has such massive, all-flying canards that they also work well as airbrakes after landing.
Even conventionally configured modern fighter (F-15, F-16, F-18, F-22, F-35, Sukhoi, etc.) jets are naturally unstable and depend upon electronic stability augmentation.

Even Burt Rutan recognized the limitations of canards and reverted to conventional configurations (Grizzly, Catbird, Boomerang, etc.) late in his design career.
 
riggerrob said:
First, Cherokee have straight wings and horizontal tail because their quarter chord (40 percent on laminar wings) have straight leading and trailing edges, parallel. Only the vertical tail fin is swept and that is purely for fashion.
Cozy and other canards with side-by-side seating suffer problems with streamlining the aft fuselage. All light pushers suffer similar problems (see Cessna 337 Skymaster). Similar to Republic RC-3 Seabee pusher flying boat, they need to taper the fuselage rapidly from 4 feet wide to zero on a short distance. This can create problems with turbulent or unstable airflow. Glass Goose needed to add vortex generators to stabilize airflow around the aft portion of its cockpit fairing.

Burt Rutan designed many of his canards specifically for ultra long distance record-setting, so naturally they are sluggish during take-off. If you want to see a STOL canard, look at Rutan's Grizzly sort-of-biplane.
If you want to see canard racers, look at the Amsoil biplane and Pond Unlimited Racers. Amsoil looked like a Rutan Quickie upgraded with a larger engine, conventional horizontal tail and vestigial inter-plane struts. Amsoil flew well, but never medaled.
OTOH the Pond Unlimited Racer was plagued with engine problems and crashed. That was the only time a client of mine has died with a parachute that I packed still un-opened. An engine failed before the Pond Racer pilot ever climbed high enough to bail out. It si also rumored that he was asphixiated by fumes when an engine failed.
Piaggio Avanti flies more like a conventional airplane. Because they wanted to route the main wing spar aft of the cabin pressure vessel, they split the main lifting wing into two parts. The large, middle wing provides most of the lift and has all the usual ailerons and flaps and conventional control surfaces. Avanti's forward canard is fixed (with no control surfaces) and only provides enough lift for balance. Next time you see an Avanti, look closely at the conventional elevators hinged from the horizontal portion of its T-tail.

OTOH the Rutan-designed Beechcraft Starship had a far more complex canard with trailing edge flaps and variable sweep. The variable sweep moves the canard center-of-lift forward to compensate for a nose-down pitching moment created when main wing trailing edge flaps are deployed for landing. Starship needs those trailing edge flaps to allow it to land on the same short runways (less than 3,000 feet ... er ... 1 kilometer) as its King Air predecessor.

Rutan copied his lifting canards from SAAB's Viggen jet fighter. Viggen used canards to balance a delta canard main wing. Both the Viggen's main wing and canard have landing flaps for the STOL performance desired by the Swedish Air Force.
Lifting canards require moving the center-of-gravity so far forward that it is near the leading edge of the main wing. Look at the blet buckle of the rear seat passenger in a Rutan Long Eze for an approximation of its C. of G. Placing the second occupant's seat near the C. of G. is standard practice on light 2-seaters as it minimizes balance changes when you add or delete the second occupant. This forward C. of G. aids with pitch stability ... a trait lacking in most earlier canard designs (see Curtiss Ascender and Japanese Shinden).
SAAB Viggen was the first truly successful canard airplane, but its canard configuration has been copied by several alter fighter jets (Dassault Rafale, Eurofighter, SAAB Grippen, etc.) because fighter designers want airplanes that are naturally unstable, so they can turn quicker. They are unstable because their C. of G.s are too far aft, which is great for cruise efficiency and maneuverability, but exhausting for human pilots to fly. Fortunately jet fighter "relaxed stability" is backed by 3 or 4 channel auto-pilots that automatically stabilize the airplane in cruise. Eurofighter has such massive, all-flying canards that they also work well as airbrakes after landing.
Even conventionally configured modern fighter (F-15, F-16, F-18, F-22, F-35, Sukhoi, etc.) jets are naturally unstable and depend upon electronic stability augmentation.

Even Burt Rutan recognized the limitations of canards and reverted to conventional configurations (Grizzly, Catbird, Boomerang, etc.) late in his design career.
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I should have put a smiley face after describing my High performance CHEROKEE 140.
I am actually an A&P IA 30+ years, and private pilot so I know a little bit about aircraft.
I have always been a fan of the Rutan Viggen “Sexy”, and almost bought one. The gentleman who built it didn’t want the liability of it flying and donated it to a museum.
The Amsoil racer is an extreme stager biplane. And the Pond racer was a conventional wing and tail layout utilizing Nissan V6 engines I believe. I always thought if they had moved the pilot pod forward it would have looked alot like a P38. My favorite WWII fighter.
I have actually walked around an Avanti. Like I said, love the design.
I was unaware of the Beech Starship canard short field reasoning. Makes sense. I do know that because it was an early composite business airplane the safety factors imposed by the FAA pretty much negated the advantages of the composites. Sad.
I worked on Canadian F18’s and will always be a fan.
That said I believe as a pure fighter F16 is better overall. The F18 is probably not quite as good as the European deltas.
I think pilot training would make the difference between any of these aircraft.
Oh and go Avro Arrow!
 
HoHun said:
Hi,

publiusr said:
Any combination of the two—-T-tail and canards both say?
Click to expand...

The abovementioned Rutan Catbird, for example.

Rutan goes into some of the design considerations for that aircraft here:


Regards,

Henning (HoHun)
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Good analogy describing the Catbird as a biplane with massive stagger between its front wing (aka. canard) and rear wing (er ... main wing).
 
A reason you see a practical application of the canard on Delta winged military aircraft is that highly swept or Delta wings stretch out the CG. Another issue of putting some control surfaces in the front, is you end up with force that naturally wants to work the other way around. When I was a kid (for some reason), I cut the tip off an arrow, notched it and fired it backwards. The results are obvious. It might seem an overly simplistic analogy, but a starting point none the less. Craig Breedlove lost the land sound barrier to the British because they had a tail and Breedlove had a small vertical stabilizer on the front of his. At a certain speed near 600mph, the air tightened around where that stabilizer was and his car went into a slight, but uncontrollable curve....3 or 4 times. Some stabilizers naturally work better at the rear where they work in conjunction with the drag instead of opposed to it. In some applications canards work, but at a cost.
 
A canard could have a simper swing wing set up that aircraft with true variable geometry wings.
 
publiusr said:
A canard could have a simper swing wing set up that aircraft with true variable geometry wings.
Click to expand...

That might be, but it also increases the weight substantially. What I did to solve the issue was to make it a semi-tandem configuration, where the canard was a full lifting wing carrying 35-40% of the load. Did it a small rocket launched free-flight glider and flew it 72 times. It was a great little glider.
 
Vortex control is another reason to install canards on a military jet fighter.
There are multiple ways to control leading edge vortices on deltas.
If you look at the main wing on Viggen and Tejas, you will see that the inner leading edge has only a shallow sweep while the outer leading edge has a steep sweep. This generates an extra vortex at mid-span.
Similar methods include installing sharp-edged chines on the forward fuselage (see F-16 and CF-18).
Canards can also serve that function by shedding vortices from the tips of their canards. These vortices affect airflow over the top of the main wing at mid-span.
These extra vortices help stabilize and control airflow over the top of the main wing at steep angles of attack encountered during landing and air combat maneuvering.
 
At what speed? I think canard behavior is variable depending on speed. Even between 200 and 400 mph, and again very differently past 700 or more.

I generally don't think a lot about supersonic...it's so far outta my reach or experience. . Theoretically, sure. Practically, not really.
 
EdwardA said:
At what speed? I think canard behavior is variable depending on speed. Even between 200 and 400 mph, and again very differently past 700 or more.

I generally don't think a lot about supersonic...it's so far outta my reach or experience. . Theoretically, sure. Practically, not really.
Click to expand...
Vortex lift is really only an issue at steep angles of attack. Vortex lift is also really "draggy" so only relevant for fighters with massive amounts of excess thrust.

Supersonic canards include: Chinese Chengdu J-10, Dassault Rafale, Eurofighter, Israeli Lavi, SAAB Grippen, SAAB Viggen, etc.

The key is mounting the canard far enough aft that it stays inside the shock cone created by the nose. In some respects, this is easier with a canard than a conventional tail.
 
EdwardA said:
publiusr said:
A canard could have a simper swing wing set up that aircraft with true variable geometry wings.
Click to expand...

That might be, but it also increases the weight substantially. What I did to solve the issue was to make it a semi-tandem configuration, where the canard was a full lifting wing carrying 35-40% of the load. Did it a small rocket launched free-flight glider and flew it 72 times. It was a great little glider.
Click to expand...
Have any pics of the model you can share?

Enjoy the Day! Mark
 
Didn't the Beech Starship have variable-trim canards that allow the use of conventional flaps? I was under the impression that the inability to use flaps was the biggest drawback of the canard layout, and I really want to know more on how Rutan managed to solve that problem.
 
The Beech Starship had variable sweep canards. Swept aft for cruise (lift point moved aft, lower lift to AOA slope), forward with little or no sweep to offset nose down pitching moment from main wing flaps.
 
OldManJoe said:
Didn't the Beech Starship have variable-trim canards that allow the use of conventional flaps? I was under the impression that the inability to use flaps was the biggest drawback of the canard layout, and I really want to know more on how Rutan managed to solve that problem.
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I answered your question in post #2.
 
EdwardA said:
How many of those aircraft are also fitted with a rear elevator, or full length Delta wing?
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Canard plus rear elevator are only seen on the current-production Piaggio Avanti. Avanti has conventional control surfaces on its main wing and rear horizontal tail. The canard has no control surfaces. Try to think of Avanti as a conventional biplane with too much stagger between its two main wings. The primary reason that Avanti has split lifting surfaces is to allow the main wing spar to route aft of the cabin's rear pressure bulkhead.

Most current-production canard fighters (Eurofighter, Grippen, Rafale, etc.) also have full delta wings. The canard just helps increase performance at high angles of attack. The canard also helps restore nose-level trim when main wing trailing edge flaps are lowered for landing.
 
OldManJoe said:
Didn't the Beech Starship have variable-trim canards that allow the use of conventional flaps? I was under the impression that the inability to use flaps was the biggest drawback of the canard layout, and I really want to know more on how Rutan managed to solve that problem.
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Plenty of canards use landing flaps.

Rather, it is pure deltas and pure flying wings that have difficulty deploying landing flaps. If they only deploy trailing edge flaps, they pitch nose-down, because the flaps move the center-of-lift close to the trailing edge and a long way aft of the center-of-gravity.

You can count on one hand the number of flying wings that have landing flaps. These are usually split flaps installed under the center-of-gravity (Armstrong-Withworth A.W. 52 jet of 1949 and the Canadian National Research Council's tail-less glider of 1946). The NRC glider was designed by British engineer T.R. Hill who had worked on the Pterodactyl series of tail-less biplanes before WW2.

A modern example is the 1989 SWIFT (Swept Wing with Inboard Flap for Trim) foot-launched glider that has so much wing-sweep that the pilot sits with his head behind the center trailing edge and the center trailing edge can be pulled down to change the lift coefficient for soaring. The flap(s) occupy a full 42 percent of the trailing edge span, with elevons making up the remaining 58 percent. This extremely-swept configuration puts both the pilot's seat and center trailing edge near the center-of-gravity.
If a flying wing had ridiculously-swept wings, the center-of-gravity could be outside the airframe, theoretically hovering somewhere aft of the center section. That would position the center trailing edge too far forward to function as landing flaps.
Hah!
Hah!

Canards are one way to compensate for that nose-down pitch.
Another way to trim pure deltas is to lower leading edge flaps. Look at the leading edge flaps installed on shallow-swept, inboard leading edges of the Indian TEJAS light fighter. Slightly lowering those LE flaps can move the center-of-lift forward to balance the extra lift generated by trailing edge flaps. OTOH raising those LE flaps can create massive amounts of drag to help brake after landing.
 
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Canards do not need relaxed-stability or fly-by-wire to deploy flaps for landing. Both SAAB and Rutan proved that.
 
I assume you are referring to the Viggen and Starship. The Starship is a bad example. The flaps were basically worthless. The were better suited as speed brakes. As a matter of fact, the follow-on Starship (II), prior to line closure, had the flaps removed because the added weight did not justify the minimal effect of the flap. The Viggen is also a bad example. The Viggen had a relatively sophisticated SAS system for its time to keep everything pointed in the right direction. Additionally, the flaps you refer to, were on the canard, not the wing.

As I said before, to have effective wing flaps on a canard aircraft, relaxed stability with fly-by-wire is pretty much mandatory.
 
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After reading and thinking about wing root intakes, canards and my carrier aircraft idea, I thought all of this could be combined.

As to my understanding, the canards are working with a higher inclination and wing load than the main wing, so that they stall first. Combined with the low wingspan of the canards, this will cause high induced drag by wingtip vortexes. The wingtips of a canard would be therefore an ideal place for wingtip propellers which can counteract the vortexes. Unlike positioning them on the main wing, the yaw control with one engine out would be much less problematic due to the lower wingspan.

The Do 28 ( https://en.wikipedia.org/wiki/Dornier_Do_28 ) wasn’t really meant to be a three wing plane and the rotation of the propeller was identical for both sides, but it could give an impression of how it could look like (with the wings more forward and a larger span). Same is true for this here

https://www.secretprojects.co.uk/th...livery-airplane-for-us-navy.39087/post-642513

The aerodynamic best solution for engine coolers is an integration in the wing. https://www.secretprojects.co.uk/th...hey-still-be-relevant-today.35041/post-643963

As written, this is easier said than done, because there is also other stuff in the wings, like wingspars, fuel tanks, flap mechanism etc.. Due to the lower wingspan, the canards, especially in a three wing plane, will have a significant lower wing root bending moment which would make it a lot easier to place the engine coolers integrated in the canards than in the main wing. This solution would also allow a split flap which would serve two purposes, managing the amount of cooling air flow and produce lift during landing and take off. The position in the very front of the aircraft will help to reduce the nose down moment. Please excuse the crappy drawing, but I think it makes clear what I mean:
 

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Nicknick said:
After reading and thinking about wing root intakes, canards and my carrier aircraft idea, I thought all of this could be combined.

As to my understanding, the canards are working with a higher inclination and wing load than the main wing, so that they stall first. Combined with the low wingspan of the canards, this will cause high induced drag by wingtip vortexes. The wingtips of a canard would be therefore an ideal place for wingtip propellers which can counteract the vortexes. Unlike positioning them on the main wing, the yaw control with one engine out would be much less problematic due to the lower wingspan.

The Do 28 ( https://en.wikipedia.org/wiki/Dornier_Do_28 ) wasn’t really meant to be a three wing plane and the rotation of the propeller was identical for both sides, but it could give an impression of how it could look like (with the wings more forward and a larger span). Same is true for this here

https://www.secretprojects.co.uk/th...livery-airplane-for-us-navy.39087/post-642513

The aerodynamic best solution for engine coolers is an integration in the wing. https://www.secretprojects.co.uk/th...hey-still-be-relevant-today.35041/post-643963

As written, this is easier said than done, because there is also other stuff in the wings, like wingspars, fuel tanks, flap mechanism etc.. Due to the lower wingspan, the canards, especially in a three wing plane, will have a significant lower wing root bending moment which would make it a lot easier to place the engine coolers integrated in the canards than in the main wing. This solution would also allow a split flap which would serve two purposes, managing the amount of cooling air flow and produce lift during landing and take off. The position in the very front of the aircraft will help to reduce the nose down moment. Please excuse the crappy drawing, but I think it makes clear what I mean:
Click to expand...
Your drawing reminds us of the engine cooling radiators submerged in the wings of Messerschmitt Bf.109 and Supermarine Spitfire.
Others will tell you that Meredith radiators buried in the aft fuselage are the most efficient. At best, Meredith radiators neutralize cooling drag. Meredith radiators benefit from the huge volume available inside the fuselage to expand and slow cooling air flow to allow it the longest possible time in contact with hot radiator coils. BY that same logic, the longer the wing chord, the larger and slower radiator you can install.
But neither are really relevant until diesel engines become fashionable on airplanes. Diesels have the advantage of burning jet fuel, diesel fuel, home heating oil, etc. Multi-fuel becomes important as soon as you fly away from major airports in the middle of North America. Arctic bush pilots mainly operate turboprops because 100 octane low lead is scarce in Alaska or the Canadian High Arctic. Avgas can be even more difficult to source in deepest, darkest Africa.
 
Please note my last link in the post above, there I allready mentioned the cooling system of the BF 109 and also linked this here (http://109lair.hobbyvista.com/techref/systems/cooling/f_flaps.htm ). As we can see, the diffusor length was too short to be very effective, which was very likely the case because of the wing spars, weapons, landing gear and fuel tanks beeing in the way. Because of these constrains, the intake was at the bottom of the wing and not in the front, which would have been the best solution. Placing the cooling system in the rear fuselage ment to use quite the only area of a fighter plane which is relativly empty and allows sufficient space. The drawback is, that you need an intake with a boundery layer seperation which protudes out of the fuselage and causes additional drag. Also, the outflowing warm air will cause increased friction on the belly of the aircraft. Wing intakes can avoid this and are therefor aerondynamically the best solution, but mechanical constrains make them unfeasable in most cases.

Canards are less stressed mechanically and usually don't contain a landing gear or fuel tanks (nor guns or canons...), therefor it would be much easier to integrate a cooling system in the canards instead in the main wings. Placing two (Diesel) engines on the end of the Canards as wing tip engines could also give some benefit, so the combination is better than the sum of its single components.

I did my very best to make Aero Diesels more popular and made a research project for developing a Diesel Aero engine (265 kW, 235 kg, about 190 g/kwh at cruise), but our project partners didn't really help us a lot and so we ended with a finished design (including all necessary FEM and thermodynamic simulations) and a half finished engine. Wihout fundings, chances are low it will ever be finished...

BTW the liquid cooled boxer configuration of our design would have enabled it to use an efficient cooling system below the engine for typical SEP (I made a concept study for a power egg) The Continentals and Austro Diesels usually have terrible unefficient cooling systems which lack a proper diffusor and ejector because there is no space left around them.
 
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Nicknick said:
After reading and thinking about wing root intakes, canards and my carrier aircraft idea, I thought all of this could be combined.

As to my understanding, the canards are working with a higher inclination and wing load than the main wing, so that they stall first. Combined with the low wingspan of the canards, this will cause high induced drag by wingtip vortexes. The wingtips of a canard would be therefore an ideal place for wingtip propellers which can counteract the vortexes. Unlike positioning them on the main wing, the yaw control with one engine out would be much less problematic due to the lower wingspan.

The Do 28 ( https://en.wikipedia.org/wiki/Dornier_Do_28 ) wasn’t really meant to be a three wing plane and the rotation of the propeller was identical for both sides, but it could give an impression of how it could look like (with the wings more forward and a larger span). Same is true for this here

https://www.secretprojects.co.uk/th...livery-airplane-for-us-navy.39087/post-642513

The aerodynamic best solution for engine coolers is an integration in the wing. https://www.secretprojects.co.uk/th...hey-still-be-relevant-today.35041/post-643963

As written, this is easier said than done, because there is also other stuff in the wings, like wingspars, fuel tanks, flap mechanism etc.. Due to the lower wingspan, the canards, especially in a three wing plane, will have a significant lower wing root bending moment which would make it a lot easier to place the engine coolers integrated in the canards than in the main wing. This solution would also allow a split flap which would serve two purposes, managing the amount of cooling air flow and produce lift during landing and take off. The position in the very front of the aircraft will help to reduce the nose down moment. Please excuse the crappy drawing, but I think it makes clear what I mean:
Click to expand...
For an aircraft without a stability augmentation system (as far as I'm aware, no general aviation airplanes have a stability augmentation system, although some bizjets have stickpushers), the forward surface -- canard or wing -- has to stall first, so the canard cannot have enough pitch authority to stall the main wing. This generally means that the main wing cannot have lift-increasing trailing edge flaps, as these increase wing camber and increase the wing's nose-down pitching moment: if the canard has enough authority with flaps down, it has enough authority to stall the main wing flaps up, with results likely to be disastrous. One could, I suppose, set up a linkage between the flaps and canard restricting the canard's deflection flaps-up.

Another problem for small general aviation canards is the location of internal volume: where does one put the fuel tanks? Ideally, fuel tanks are as close to the c/g as possible, which is why putting them in the wings of conventional (wing-first) aircraft is so convenient. This isn't really possible with a canard, where the wing is behind the c/g.
 
If I get you right, the stall problem is not caused by an aerodynamic slip stream of the canards, but simply due to imbalance if the canards would be using flaps and the main wing not. Synchronizing the flaps on two wings wouldn’t need a complex stability program, it could be a very simple software function on electric flaps or, as you mentioned even a mechanical system (e.g. by Bowden cables). In times of fly by wire, we should have enough trust in electric controls to do that.

I was more thinking on a three wing design like the Piaggio Avanti, with a bit larger canards which would carry the engines and a conventional tail for the controls. The main wing would be more or less in the same position as on conventional planes.
 
1635yankee said:
For an aircraft without a stability augmentation system (as far as I'm aware, no general aviation airplanes have a stability augmentation system, although some bizjets have stickpushers), the forward surface -- canard or wing -- has to stall first, so the canard cannot have enough pitch authority to stall the main wing. This generally means that the main wing cannot have lift-increasing trailing edge flaps, as these increase wing camber and increase the wing's nose-down pitching moment: if the canard has enough authority with flaps down, it has enough authority to stall the main wing flaps up, with results likely to be disastrous. One could, I suppose, set up a linkage between the flaps and canard restricting the canard's deflection flaps-up.

Another problem for small general aviation canards is the location of internal volume: where does one put the fuel tanks? Ideally, fuel tanks are as close to the c/g as possible, which is why putting them in the wings of conventional (wing-first) aircraft is so convenient. This isn't really possible with a canard, where the wing is behind the c/g.
Click to expand...
Rutan solved the problem of where to store fuel by adding large, sharply-swept wing root strakes to his Vari-Eze, Long-Eze and Defiant light canards. Their strake-mounted internal fuel tanks were adjacent to the rear seat passenger, hence near the center-of-gravity.
Locating fuel tanks in wing-strakes also reduces risks - from fuel leaks - during crashes.
 
riggerrob said:
Rutan solved the problem of where to store fuel by adding large, sharply-swept wing root strakes to his Vari-Eze, Long-Eze and Defiant light canards. Their strake-mounted internal fuel tanks were adjacent to the rear seat passenger, hence near the center-of-gravity.
Locating fuel tanks in wing-strakes also reduces risks - from fuel leaks - during crashes.
Click to expand...
Also means you don't have any weirdness with fuel piping in the wings. You see, the wings on an EZ are bolted on, held in place with 2 bolts each in conical bushings. But if you build the whole fuselage first, you can run the engine immediately, without having to haul the plane to an airport.
 
I'm reminded there was a light canard 'hauler' prototyped, name currently eludes me. Ex-RAF guy's name was long and unusual...
Aha !!
en.wikipedia.org

Lockspeiser LDA-01 - Wikipedia

en.wikipedia.org en.wikipedia.org
I'd call it a canard but, as canards' area equalled half a main wing, for better parts commonality, purists would say it was 'tandem'.
Straight, bolt-on, high-set wings, fixed tricycle undercarriage.
Sub-scale prototype had single rear engine & prop, but full-sized to have two wing-mounted, allowing tail-gate hatch., with load-space specifically designed to carry a couple of wings...

Yes, intended for bush / utility work. Not quite STOL, IIRC, but certainly 'short, rough field'.

IIRC, the big 'canard' allowed a 'prompt' pull-up to nose-high attitude for 'low & slow', the fixed undercarriage protecting rear prop...

As I recall, the sub-scale prototype had admirable handling characteristics, seemed to lack any vice.
Only snag was financing...

Okay, yes, the LDA-01 straddles the canard and tandem categories, but I feel it deserves a mention...
 
Like the unfortunate Optica, a STOL twin-boom pusher with helo-bubble cockpit, it was just too different, and unlucky besides...
 
Interestingly it was said, that the plane could work with a wide range of CG positions, that’s something which is unusual for Canards. I love the Optica, but this is unfortunately completely off topic…

The name Lockspeiser is probably of German origin, I believe it was once Lochspeiser (something like “hole feeder”) and became Lockspeiser because Anglosaxens usually can’t pronounce “ch” correctly (same is true for the "ei"....).
 

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