Subject: Off subject
From: Rotary Engine
Date: 6/23/2008, 5:12 PM
To: AAA Put this in the To box


Hi Paul,

    I'm not an aeronautical engineer, so I truly don't know the answer
to this question and it's bugged me for a long time, but now that you
have some interest in the canard (I think it was a Cozy you were looking
at, but I don't have the specific email now, so I'm not sure) perhaps
you'll roll this one over in the back of your mind in-between all the
other questions you consider.  Is there any practical, simple, efficient
way to put flaps on a canard airplane?
    The prevailing belief is just to "keep it simple" and land pretty
fast.  The adage "When you fly fast, you land fast" still seems an
impregnable wall, but does it have to be that way especially on
composite aircraft where damned near any structural form and light
weight is possible?  Everyone says "It's just too complicated, but is it
really?  Looking at it through rather foggy glasses, I can see that you
would dramatically increase the potential for flutter, but are the
mechanics and dynamics of it as tough as we hear for aircraft that will
always likely be in the 200 to 300 knot range for the vast majority of
designs?  If that nut could be cracked, it looks like the canard could
be a very fast heavy lifter that was also very forgiving.  Any thoughts?

Robin

Flaps cause a pitch down moment on any aircraft as they move the center
of lift aft on the wing.

The canard  Beech Star ship swept the canard back for flight
and forward for landing with flaps to counter the pitching moment.
It can be achieved if you mount the canard on rails and move it back
and fourth.

The energy in a crash is the square of the crash speed.
That is why the FAA specified 61 kts for the stalling speed
of single engine aircraft. If you crash a twin or a common run of the mill
canard consider yourself dead :) Yes.. they don't stall. They just fall out
of the sky. Anything will fall out of the sky if you get it slow enough. If
you
are too close to the ground and the canard stalls you are going
to hit real hard on the nose. If you are in a hard turn and the canard
stalls
the airplane is going to make a sharp turn towards the ground.
-- 
Paul Lamar ...No rotor no motor.

Paul,
That is exactly the way we are also countering the cg problem of side by
side seated canards. The problem with large canards, is with one light pilot
and no passenger, you don't have enough down trim, as the canard is loaded
too light. Put in a large pilot and a large front passenger, and now the
canard is overloaded and you run out of up trim. We calculated it will take
14 inches of travel on a large canard to correct this based on cg change. It
would take more to make up for flaps. The beautiful thing with this, the
screw to change the position based on cg is also the trim mechanism. You
just end up with a graph showing the correct canard position based on the
total weight of the front seat pilot and passenger.
The rear passengers and fuel sit on the cg and have little effect.
The other thing that could be done with added complexity is leading edge
slats of one type or another. These would help counteract the center of lift
change of the flaps, just at added weight and complexity.
Larry



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