Re: Reflex

Jay Scheevel

The reflexor was an approved mod by QAC. It was sold as a retrofit kit or as an option by QAC in the very latest kits they sold. Usage recommendations are addressed in one of the QAC newsletters, but I don’t remember which one. The range of up 6 degrees to down 2 degrees is recommended.


I have been trying to determine the significance of those numbers and establish limits for my own plane, so I can do what Jerry recommends and put limit stops on mine. To do this, I have been modeling the effect of a range of reflexor settings on my airplane’s decalage of -1.5 degrees, meaning the canard is 1.5 degrees higher angle than plans built. The factory prototype was a -1.0 degree decalage, meaning its canard was leading edge up 1 degree wrt plans. Jerry’s plane has a decalage of +1, meaning his canard angle relative to wing is 1 degree leading edge LOWER than plans. I have personally measured this on his plane.


The first graph below is how different decalages fly (angle of attack/alpha vs elevator setting). Each colored curve corresponds to a different decalage. The black contours are airspeed, so at the right side of the graph is where the at highest angle,  elevator and lowest speed (in graph is in ground effect). Jerry’s plane should follow the dark green line when no reflexor is used, so without reflexor he will arrive at the ground with his plane around 4.5 degrees. His taxi angle is 4.5 degrees, so he would land 3 point. If he reflexed trailing edge down, it would indeed slam his nose into the ground even with full elevator as he has said.  This is not the case for his landings, because he is using a highly reflexed trailing edge up when landing.


So how does reflexor change the curves in the first graph? I have been modeling this for my plane only on the second graph. With no reflexor, my plane will fly the green curve, and I will arrive at the ground with an angle of about 6.5 degrees, This is 2 degrees higher than Jerry, because my declage is about 2.5 degrees different from his. If I reflex up 6 degrees (-6 by my sign convention), I will land at angle of a little over 8 degrees, so the change in alpha at landing caused by reflex is about 0.25 degrees of alpha increase for each degree of trailing edge up deflection of reflexor.


Jerry actually lands at about 8 degrees angle, so his reflexor, according to my modeling is up about 14 degrees. This would correspond to more than 1 inch of up deflection at the trailing edge. Seems high, but Jerry can let me know if I am off base.


Anyway, as Sam H. says: “Your results may vary”. I would only add the following:  You need to know your decalage before you will know what your reflex limits should be. If you have a decalage of -1.0 like the QAC factory prototype, then you would want to use the factory recommendations of up 6 degrees to down 2 degrees.



Jay Scheevel, Tri-Q, still building




From: Q-LIST@...
Sent: Friday, March 16, 2018 4:26 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Reflex



I like to use aileron TE down for approach till touch down. This assures a good visibility of the approach and maximum main wing lift.  It is easily overcome with elevator control while near touch down and once I’m on all three wheels I dump to reflexor TE up. 


To my mind this plane is guaranteed to stay on unless I add power. 



On Mar 16, 2018, at 2:08 PM, Mike Dwyer q2pilot@... [Q-LIST] <Q-LIST@...> wrote:


The Q200 plans definitely had a reflexer altho I think it was an option?

I use the aileron up all the time but have never used aileron down.  

The down stop is a good idea.  Next time I have mine apart I'll look into that.

1300 hours in Q200.

Mike N3QP




On Fri, Mar 16, 2018 at 1:42 PM, Jerry Marstall jnmarstall@... [Q-LIST] <Q-LIST@...> wrote:


I don't remember the original plans having a reflexor




Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: "Kris l_kris_browne@... [Q-LIST]" <Q-LIST@...>
Date: 3/16/18 11:57 AM (GMT-05:00)
To: Q-LIST@...
Subject: Re: [Q-LIST] Reflex


The original plans design calls for 6 degrees up and 2 degrees down - I am not aware of any deviations from this spec.




From: Q-LIST@... <Q-LIST@...> on behalf of Dorothea Keats dkeats@... [Q-LIST] <Q-LIST@...>
Sent: March 15, 2018 3:53 PM
To: Q-LIST@...
Subject: [Q-LIST] Reflex



What is everyone using for the relexor limits.  On my Dragonfly I have
maybe 3/8ths up and down, but I feel the Q200 may be a bit more. What
would a safe starting point for the up and down movement at the trailing
edge of the aileron.?
Thanks----------------  Chris


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