shoeless(at)barefootpilot
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 Posted: Wed Aug 23, 2006 8:53 am Post subject: Tri gear vs tailwheel for short take-off, was: Is a taildra |
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ken wrote:
"I think I read on this list some time ago ( a year or more) that the nose
wheel Kitfox can take off and land a little shorter than the tailwheel
version"
Ken,
I believe this to be true. John McBean is likely the best authority on this
subject.
While I have not actually tested a tri-gear vs. tailwheel kitfox (partly
because it's difficult to find two similarly configured) I do have some
empirical evidence to support the idea that a trigear can take-off and land
shorter...
Recently, I switched tires from 600x6 to 850X6. The taller tires allow the
wing to sit at a higher angle when on the ground in the 3 pt position. This
higher angle allows my plane to take-off 75' shorter than before. (5100'
elevation airport) Test were done on two subsequent days in identical
conditions.
I have commented about this wing angle issue before. The sitting position of
the plane puts the wing at an angle that is well below the angle at which
the wing will stall on landing. Because of this, a TRUE 3 pt, full stall
landing in a kitfox (models 4 and higher are the ones I refer to here) will
cause the tailwheel to touch down first. (by a significant amount in the
kitfoxes I have flown) This angle also lengthens the take off roll. With
wing sitting at this low angle, the plane must accelerate to a higher speed
before liftoff than if the wing were at a higher angle.
Now I realize that some people will comment that their kitfox can stall and
land in 3 pt position without the tailwheel touching first (or at least not
by a significant amount) But I would counter that by suggesting that your CG
may be such that you don't have the elevator authority to really stall it
hard, especially in ground effect.
Following this logic, a tri-gear plane could rotate so that the wing is at
the optimum angle for short take-offs and landings, thus outperforming a
similar tailwheel airplane. In addition to this, a trigear plane has less
drag initially in the takeoff roll, thus allowing it to accelerate faster.
Despite this, I would never switch to a tri gear airplane because many of
the off-airport places that I land would leave a tri gear fox with it's nose
buried in the ground.
There is a nice article on STOL aircraft design on the Zenair web site:
http://www.zenithair.com/stolch801/design/design.html
Best Regards,
Cliff
S5, Erie, CO
I think I read on this list some time ago ( a year or more) that the nose
wheel Kitfox can take off and land a little shorter than the tailwheel
version because of the ability to get a little more rotation and thus a
greater angle of attack. Does anyone else remember that discussion? I made
the tailwheel decision and purchased the parts before I heard about this.
That being said I am staying with the tailwheel - logic aside. I have
tailwheel experience, I like the looks, and I like being in the fraternity
of the few pilots who fly tailwheel airplanes.
Ken Jones
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