Canards

[x-wind]

In my theory of flight class, my instructor was talking about canard style airplanes. He talked about how they are generally more efficient. The only down side to them, and the reason there not more widely used, is that they have a longer takeoff and landing distances. Additionally he said one main reason they don't get used by major air
carriers is because of the current airport setups. i.e. docking equipment.

Its impressive what Burt Rutan has done, I am just wondering why we don't see more of these planes.

[ice ice baby]

I might be worng but I thought Canards perform worse than conventional horizontal stabs under icing conditions. Canards sure look cool on a slick looking single.

[ZLIN 142C]

The main reason that a canard planform is more efficient is that the canard does double-duty as a lifting surface in addition to providing pitch control. The horizontal tail in a conventional aircraft deflects air upward to counter the natural nose-down pitching tendency, which is itself due to the C of G being ahead of the Centre of Pressure. As such, the tail contributes nothing to lifting the aircraft. The canard deals with this same pitching tendency by adding lift ahead of the C of G. Since its lift vector is acting in the same direction as the mainwing, it generates less drag doing its job.

The canard has a much higher wing loading than the mainwing, and reaches critical AOA much sooner, thus stalling first and unloading the mainwing. In theory, the mainwing should never stall, which is the main safety reason for the canard in the first place. This does have a consequence, however. The canard is a highly loaded critical lifting surface, so ice has a very immediate effect.

But probably the major reason that we don't see more aircraft with this layout has more to do with perception. To most people, a canard just doesn't look "right". That had a lot to do with the failure of the Beech Starship, a fine aircraft in my opinion that met with a fate it did not deserve. (Burn in Hell, Raytheon beancounters, for cutting them up.)

Anyway, X-Wind, this is my understanding of the subject. I happen to be a great fan of unconventional aircraft. And Burt Rutan is one of my heroes.

Cheers.

[I_Drive_Planes]

The only down side to them, and the reason there not more widely used, is that they have a longer takeoff and landing distances.

I find this difficult to believe considering the wren conversion available for the Cessna 182

http://www.260se.com/performance.html

Check those takeoff and landing numbers!

Planes

[fougapilot]

To the best of my knowledge, the reasons they have a longer takeoff and landing distances has nothing to do with the canard. You see, most canards available on the market today are kits that one must built in his basement (burn in hell Raytheon for making it so...). This amateur built market is simply tailored for the individuals who want more "bang for the bucks". So the designers concentrate on making these kits as fast as possible on the smallest engine possible. Since speed is determined by the drag a specific airframe generates, the designers decrease the drag to its absolute minimum. This includes rivet less airplanes (composite) lightweight (again composite) and a thin (high aspect ratio) wing that need all the excess speed to get off the ground. I am convinced if one really wanted, one could make a STOL canard. After all, the Wright brothers flew a canard on the beach in 1905...

As for why they are no more widely used? I agree with ZLIN. You see at the end of the day it all comes down to $$. If an airplane doesn't look "right" people wont want to fly it. If pax don’t want to fly in it, airlines wont buy it. If airlines don’t buy it, manufacturer wont make it. This is what happened to the Starship. Marvellous airplane. So few were actually sold, probably because of its un-conventional look, that it was cheaper for Raytheon to buy them ALL back 20years after they were originally sold instead of providing the technical support (parts, Airworthiness directives...). The Starship is no longer on the endangered species list, it is now extinct.

The fact is; if the original Wright canard had become the norm over the years, we would today have a canard 747 and 340 and they would be more fuel efficient for the same missions.

Long live Burt Rutan…

[ScudRunner]

I saw one of those 182 with the canards on it come through YXY last summer. Very interesting Aircraft had all sorts of VG and Fences on it. The thing was loaded to the tits and jumped into the air. Strange looking bird but id love to give her a spin to compare its performances.

[rigpiggy]

The starship died because it was fat, cost more than a 200 for roughly same performance, couldn't use the short strips. the canard on the wren unloads the wing and tail, and is is direct propwash increasing it's effectiveness. canards also have some control issues in that they tend to be attitude stable rather than airspeed. this means when you have to pay more attention. The piaggio avanti is a very elegant solution, to this problem the canard unloads the tail of most trim drag, while still leaving the horizontal stab for control and trim. the avanti also has flaps on the canard that are linked to the main flaps, this offsets trim change required with flap selection.

[Canus Chinookus]

Canard? isn't that a mentally handicapped canadian?

[fougapilot]

Canard? isn't that a mentally handicapped canadian?

Is there any other kind???

[medby]

.

[x-wind]

Thanks for the info. Im really glad you expanded this subject for me. Im going to continue researching them I find them intresting.

[ZLIN 142C]

The starship died because it was fat, cost more than a 200 for roughly same performance, couldn't use the short strips. the canard on the wren unloads the wing and tail, and is is direct propwash increasing it's effectiveness. canards also have some control issues in that they tend to be attitude stable rather than airspeed. this means when you have to pay more attention. The piaggio avanti is a very elegant solution, to this problem the canard unloads the tail of most trim drag, while still leaving the horizontal stab for control and trim. the avanti also has flaps on the canard that are linked to the main flaps, this offsets trim change required with flap selection.

Actually, the Avanti isn't technically a canard layout, since the forward surfaces are not used for pitch control. It's more accurately called a three-surface layout. This is a detail, however. You are right in that this layout unloads the horizontal stab and makes the whole arrangement far more efficient, which is one reason the Avanti performs as well as it does.

Regarding flaps, the Starship's solution to this was to have a variable-geometry canard that swung forward when the flaps were lowered. I won't debate you on the merits of the Starship - IMHO it was a fine aircraft that should not have died as it did. However, there were development issues, and the improved performance over the King Air did not materialize. But with refinement in production, I think all these things could have been resolved.

The Starship was launched too early, I believe. Look at the Avanti - it is a contempory of the Starship, but didn't go into production until recently, and only then due to the faith of Ferrari in making the investment to produce it. But the world is ready for such an aircraft now. There is an excellent article in Air&Space from a few months back on the demise of the Starship, and it explores many of the issues you mentioned as well as those I did. If you can find a back issue, I highly recommend it.

[fougapilot]

Look at the Avanti - it is a contempory of the Starship, but didn't go into production until recently, and only then due to the faith of Ferrari in making the investment to produce it.

Not entirely true, Altough we are now only seeing an uprise in Avanti sales, the airplane has been around for quite some time. It first flew in 1986 and certification was obtained in 1990. First North American deliveries were made in the early 90s. The project just didn't catch airplanes buyers eyes until Piaggio joined forces with Ferrari in 1998.

D

[ZLIN 142C]

Your information is a little more complete than mine. I stand corrected, but my impression is that the aircraft didn't really achieve production in any sort of numbers until Ferrari got involved. In any case, it's a marvelous aircraft, but it sure had a long gestation period. Nice to see it catching on now though.

[rigpiggy]

if i remember correctly they initially sold around 60 in the early 90's. when ferrari took over, they did aminor redesign "aluminum tail ", and with the increase in oil prices, the sales have increased. yes it is a tslc. but the main thing being that the canard unloads the tail reducing trim drag. this allows a smaller wing and tail further reducing drag, with the main structural components. ie wing spar, pressure bulkhead, and landing gear hardpoints on one piece they further reduced the weight. this with a laminar wing, and a basic area ruled fuselage, they are phenomenal performers

[ZLIN 142C]

They are that. Beautiful and exotic - right up there on my list of aircraft I'd like to fly. Hard to believe they achieved that shape with aluminum.

[rigpiggy]

As I understand a combination of vacuum and hydroformed. on my list along w/ the f104 and bae 146. which I'll probably never fly either

[Bede]

The reason canards have a longer takeoff distance is because a canard needs to reach a much higher speed to rotate - the canard has to lift the nose, then the main wing can start producing lift. With a tail, the tail provides downforce early in the take off roll and the wing can start producing lift earlier.

[rigpiggy]

a lot of that has to do with gear/wing geometry. ie: with the main gear so far back the they have an extended wheelbase/ more centralized cg which requires more lift to rotate the bulk of the weight . this is why the rutan designs are parked with the noseheel retracted. w/o the weight in the cockpit, they are more sensitive to tip backwards. the starship not having this option, had to compromise, which consequently raised the minimum unstick speed