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Why Are The Vast Majority Of Canards Pushers?  
User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Posted (1 year 4 months 1 week 3 days 12 hours ago) and read 4247 times:

Just curious.

The classic modern canard right here (Rutan Long-EZ):


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In another tech/ops thread I'm involved in, another poster mentioned that the canard mounting point is a "busy" area of the plane's structure. I could see how putting an engine in there would just make things a mess.

It seems in the case of the Beech Starship, they *could* have used a tractor configuration, although the engine nacelles would have to have been longer to keep the props from hitting the swept leading edge of the wing. Then the aircraft would have benefitted from induced lift due to the prop wash. Then again, it is a product of Burt Rutan's mind.


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I'd bring up the Piaggio Advanti, but there seems to be considerable debate as to whether or not it's really a canard  


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
12 replies: All unread, jump to last
 
User currently offlineoly720man From United Kingdom, joined May 2004, 6810 posts, RR: 11
Reply 1, posted (1 year 4 months 1 week 3 days 12 hours ago) and read 4236 times:

You'd also have the canards sitting in a rotating prop wash which would do no favours (favors) to the aerodynamics.


wheat and dairy can screw up your brain
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 2, posted (1 year 4 months 1 week 3 days 10 hours ago) and read 4153 times:

I'd think a canard needs clean airflow to the canard and to the wing leading edge to be most efficient.

Which more or less requires canard prop aircraft to be pushers.

Even the jets with canards would be considered pushers.


User currently offlineprebennorholm From Denmark, joined Mar 2000, 6481 posts, RR: 54
Reply 3, posted (1 year 4 months 1 week 3 days 9 hours ago) and read 4115 times:

It's mostly a center of gravity issue.

A canard must have its center of gravity much further back than an ordinary plane. That would be hard with a heavy engine up front.

Quoting oly720man (Reply 1):
You'd also have the canards sitting in a rotating prop wash which would do no favours (favors) to the aerodynamics.

Prop wash doesn't do any favor to ordinary planes either. But for center of gravity reasons it is on even bigger disadvantage to have the weight of the engine in the tail.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 4, posted (1 year 4 months 1 week 3 days 3 hours ago) and read 3958 times:

Quoting prebennorholm (Reply 3):
Prop wash doesn't do any favor to ordinary planes either

Accelerated airflow due to propeller slipstreams creates extra lift over certain sections of airfoils    And most prop airframes take advantage of this in some form or another...



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineScooter01 From Norway, joined Nov 2006, 1205 posts, RR: 8
Reply 5, posted (1 year 4 months 1 week 2 days 23 hours ago) and read 3877 times:
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There are conversion kits available for the specially interested group of pilots that needs STOL capabilities on their Cessnas. WREN, Robertson, etc.

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Here's also a video that explains a lot of the issue:
http://www.youtube.com/watch?feature=player_embedded&v=5eSFqGyKgsw

Hope this clears up something....


Scooter01



"We all have a girl and her name is nostalgia" - Hemingway
User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 6, posted (1 year 4 months 1 week 2 days 17 hours ago) and read 3801 times:

Quoting Scooter01 (Reply 5):

Interesting. That one's new to me. Having intimate knowledge of the Cessna 182 nose area, I'm wondering how the canard interfaces structurally with the airframe. The only relatively beefy part up there is the engine mount  



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinemrocktor From United States of America, joined Jan 2005, 1668 posts, RR: 49
Reply 7, posted (1 year 4 months 1 week 2 days 12 hours ago) and read 3730 times:

Quoting prebennorholm (Reply 3):
A canard must have its center of gravity much further back than an ordinary plane. That would be hard with a heavy engine up front.

This is the answer. The more forward the CG, the higher the share of the lift being carried by the canard. Since the canard is generally already the limiting surface (since it rarely has high lift devices), you really want your CG as far back as you can get it.


User currently offlineKPWMSpotter From United States of America, joined Dec 2006, 448 posts, RR: 2
Reply 8, posted (1 year 4 months 1 week 1 day 20 hours ago) and read 3572 times:

In the designs you reference, the aircraft aren't pusher-configuration to fascilitate canard installation, the canard design was actually driven by the desire for a pusher engine configuration.

When you're powering an aircraft with a propeller, it is desirable to install the propeller in a pusher configuration. Tractor propellers are inherently destabilizing, and forward mounted engines are much harder to fair for aerodynamic efficiency. Pusher propellers are stabilizing, and allow a much more streamlined nose.

The Long-EZ configuration is just one which "works". It's aerodynamically efficient and all of the pieces are in the right place. If you shuffled the flying surfaces around to a conventional configuration (wing forward), the CG would be way too far aft. With the Starship, sure you could mount the engines the other way around, but then you would lose the stabilizing and aerodynamic benefits of a pusher propeller.

The only tractor canard aircraft I'm aware of are STOL conversions (like the Robertson STOL C182 posted above). In this case, the canards aren't true lifting surfaces, they are installed to supplement the elevators and allow more control authority at low airspeeds. In this case it's a good thing to have the canards in the prop wash, giving more control effectiveness.



I reject your reality and substitute my own...
User currently offlinenomadd22 From United States of America, joined Feb 2008, 1881 posts, RR: 0
Reply 9, posted (1 year 4 months 1 week 1 day 13 hours ago) and read 3489 times:

A lot of people don't care for the thought of debris off the wheels getting kicked up into their $3,000 props. But canards are almost stall proof. If you read the final version of the John Denver report, he had to work pretty hard at crashing his Long-Ez.


Andy Goetsch
User currently offlinedlednicer From United States of America, joined May 2005, 544 posts, RR: 7
Reply 10, posted (1 year 4 months 1 week 1 day 2 hours ago) and read 3395 times:
AIRLINERS.NET CREW
DATABASE EDITOR

There are plenty of tractor propeller canard aircraft:

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Photo © Flemming K. Fogh
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User currently offlineKPWMSpotter From United States of America, joined Dec 2006, 448 posts, RR: 2
Reply 11, posted (1 year 4 months 6 days 15 hours ago) and read 3195 times:

Quoting dlednicer (Reply 10):
There are plenty of tractor propeller canard aircraft:

Not to get bogged down in semantics, but the Quickie series and the Grizzly aren't truly canard aircraft, they are tandem wing aircraft (since the forward surface contributes a significant percentage of the total lift).

There's nothing *wrong* with installing a tractor propeller on a canard aircraft, but the configuration certainly does make it easy to install a pusher propeller (and why not install the pusher propeller when you can, it being aerodynamically superior).



I reject your reality and substitute my own...
User currently offlinedlednicer From United States of America, joined May 2005, 544 posts, RR: 7
Reply 12, posted (1 year 4 months 5 days 5 hours ago) and read 3078 times:
AIRLINERS.NET CREW
DATABASE EDITOR

I forgot three:

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