Canard vs Tail Civillian

[F-14ATomcat]

canard and tail on the pegasus

 

[Nicknick]

I think the tail of the P-400t as shown is quite bizzare. When I did some googeling for it, I found several different versions, once it was a true Canard, sometimes it had three wings, sometimes no Canards at all, and the latest version on Youtube has a T-tail. Looks like, the design team couldnt agree on a final design...

 

[F-14ATomcat]

I think the tail of the P-400t as shown is quite bizzare. When I did some googeling for it, I found several different versions, once it was a true Canard, sometimes it had three wings, sometimes no Canards at all, and the latest version on Youtube has a T-tail. Looks like, the design team couldnt agree on a final design...

There are only two variants one is flying and it is the Pe-210, it is smaller and it has canards; the P-400T has a triplane configuration.

It has canards and T tail.

There was a 3rd variant but is just a model, it has never been flown and it has canards

The P-400T it has not flown, the version I posted it is supposed to fly next year.

I guess it is triplane because it is heavier and bigger than the Pe-210, I guess they decided to adapt the T tail to off set the heavier tail because it has a heavier aft fuselage.

 

[1635yankee]

The small cross section of the long easy was enabled by the pusher design.

...and tandem seats.

 

[AndersJ]

I posted pretty much the same info and text in the J7W1 Shinden thread but I think it could help to answer some questions here as well.

I don’t think anyone is denying that a canard aircraft can be made of fly.

It's just that the question that really needs to be asked is if it’s a good idea to build a propeller powered canard type of aircraft at all, as in are they better than conventional tractor type aircraft?

Below is a figure from NASA paper 2382, where they ran a full sized Burt Rutan VariEze in one of NASA’s full scale wind tunnels.

Looking at this figure, proponent of canards may say: Yeah! That’s what I’m talking about! When the lift of the canard and main wing are combined, we get a Clmax of 1.7 at circa 22 degrees angle of attack! That’s way better than on conventional airplanes!

However, if we read the fine print in that NASA report, the reference area used to derive the impressive Clmax figure of 1.7 is based on the exposed, and not (as per aerodynamic convention) the total wing area.

On a conventional tractor aircraft, the Clmax using this total wing reference area is usually around 1.35. And using the same principle on the VariEze’s figure of 1.7, this drops to 1.32.

Well you may say, that’s not a big difference is it? 1.35 versus 1.32?

But here is the catch: Look at the VariEze’s lift slope figure above again, and you can see that you can’t take the VariEze to its full potential at 22 deg aoa, since the canard stalls already at around 15 deg aoa.

Now if we read of the Clmax for the complete aircraft there, at 15 deg aoa, when the nose drops due to the canard stalling, it’s 1.4, and which I suspect is the number Burt Rutan would like us to use. However, if we instead compare apples to apples, and use the same total reference wing area for both, then the 1.4 figure for the VariEze’s Clmax drops to 1.09, which then when compared to tractor aircraft’s typical 1.35 hardly comes off as impressive.

So in summary, you can without problems design a conventional tractor aircraft to utilize the wings full potential and extract a trimmable Clmax of around 1.35 while on the VariEze this is only around 1.09.

So why is this important? Well since you usually have a landing speed requirement, the maximum trimmable Clmax determines your wing area which is intimately coupled to the drag as in smaller wing area equals less drag.

And this is not even taking into consideration the canard's problems to handle the deflection of trailing edge flaps (the absolutely best way to increase an aircraft's Clmax for landing): On a tractor the added lift due to flaps is close to the CG, i.e. easy to trim out with the tails long arm of moment. While on a canard, the added lift is far aft of the CG and the canard surface has a shorter moment of arm and is already heavily loaded as outlined for the VariEze above.

Added to this comes the canard's horrific properties when the CG is a bit further to the rear than it should be (unrecoverable deep-stall anyone?), and problems with the canard's lift under icing conditions.

In summary, I think a McDonnel Douglas engineer said it best when a journalist asked him about the best place to put a canard when he was asked this question sometime back in the seventies:

"That would be on somebody else's airplane!"

 

[Nicknick]

In the end, Canards, just like flying wings need to have more lift capability in their wings for landing, than what it otherwise would have been needed for cruise, due to the problems of installing flaps. A logic consequence is, that these airplanes are well suited for flying at high altitude with low induced drag. Unfortunately, flying wings are not ideal for pressurization because they don't have a round fuselage. Canards are better suited for pressurisation, but in case of the Cozy, the low frontal area was realized by being a pusher plane with an oval fuselage, also not ideal for pressurisation (but surly doable).

There has been one attempt to build a canard aircraft for this in my view ideal application, the failed “Raptor” aircraft (there was quite a lot of attention on Youtube for it). Unfortunately its builder had no clue of thermodynamics/turbocharging as well as mechanical engineering was to stubbing to react to any of the advices (none from me) which were given to him in the comment section. The two stage turbocharging with a way to small low pressure turbo (about the same size as the high pressure turbo) was robbing the power of the engine and the final belt drive with its airframe fixed propeller shaft and engine fixed drive shaft collapsed so he crash landed in a field.

Despite the unfortunate end, the idea of using two stage turbocharged Diesel engine which would (if done right) be well suited for very high altitudes and efficient pressurisation (due to the two stages compression) in combination with a canard plane was a very promising approach. If done right (easier said than done) it would have resulted in a fast and very efficient plane.

 

[HoHun]

Hi,

Rutan's varieze/longeze great performance advantage over conventional two seat GA aircraft comes from three factors: much smaller crossection thanks to cramped tandem seating, extremely smooth surfaces if built right thanks to no protruding rivets and few surface gaps or other excrescences and gross weights 50-75% of what a more common GA aircraft.

Good post! My question would be, has anyone ever built a comparable aircraft with conventional layout that delivered similar performance to the Varieze/Longeze? I don't know much about homebuilt aircraft ...

Regards,

Henning (HoHun)

 

[Scott Kenny]

Good post! My question would be, has anyone ever built a comparable aircraft with conventional layout that delivered similar performance to the Varieze/Longeze? I don't know much about homebuilt aircraft ...

My instructor with the EZ had a rivalry with a guy with a Lancair 2-seater with an O235 (so a bit more horsepower than the O200 in the EZ). The EZ needed to do some aerodynamic tricks to make up for the reduced horsepower. Dogtooth outer leading edge extensions, adding lower winglets in addition to the usual upper winglets. Had the USAF vets that had some composite experience do the work for him as extra credit, IIRC.