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Author Topic: Elevator A/R on a Flapless Plane  (Read 817 times)

Offline Kim Mortimore

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Elevator A/R on a Flapless Plane
« on: May 24, 2010, 09:33:33 PM »

On a flapless plane, does the aspect ratio of the elevator make a difference, or is it just the total area of the elevator that matters at any given angle of deflection (holding the fuselage length constant)?  I'm thinking of desensitizing an oversensitive plane with an excessively large elevator without reducing the total tail volume by cutting the elevator longitudinally (without removing it) into 3 sections: a larger central section of functioning low A/R elevator and two smaller "tips" which will be made fixed. 

This will allow me to bring the elevator deflection up into the range I prefer: 25 to 35 degrees.  There may not be anything technically wrong with having very little deflection on a large elevator, I just prefer what seems to me like a "normal" range. 

Thanks
Kim Mortimore
Santa Clara, CA

Offline Howard Rush

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Re: Elevator A/R on a Flapless Plane
« Reply #1 on: May 24, 2010, 10:25:51 PM »
Beats me.  Are you worried that a smaller travel would accentuate any funny properties around neutral? 
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Offline Kim Mortimore

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Re: Elevator A/R on a Flapless Plane
« Reply #2 on: May 25, 2010, 01:33:18 PM »

Partly, yes.  Also, it's easier to adjust control sensitivity if there is more than one hole in the horn that gets you in the ballpark;  the feel isn't right; and personal preference.  Anyway you answered my basic question.  Thanks.
Kim Mortimore
Santa Clara, CA

Offline Tim Wescott

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Re: Elevator A/R on a Flapless Plane
« Reply #3 on: May 25, 2010, 03:10:51 PM »
Are you sure it isn't just a too far back CG?  Have you played with it?

(Tim, who always makes _sure_ the CG is too far back before he considers himself done trimming).
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Offline phil c

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Re: Elevator A/R on a Flapless Plane
« Reply #4 on: June 09, 2010, 02:45:33 PM »
On a flapless plane, does the aspect ratio of the elevator make a difference, or is it just the total area of the elevator that matters at any given angle of deflection (holding the fuselage length constant)?  I'm thinking of desensitizing an oversensitive plane with an excessively large elevator without reducing the total tail volume by cutting the elevator longitudinally (without removing it) into 3 sections: a larger central section of functioning low A/R elevator and two smaller "tips" which will be made fixed. 

This will allow me to bring the elevator deflection up into the range I prefer: 25 to 35 degrees.  There may not be anything technically wrong with having very little deflection on a large elevator, I just prefer what seems to me like a "normal" range. 

Thanks

The only limit is the hinge force needed to move the surface.  Low aspect ratio on the elevator increases that.  I ended up with a 4 in. bellcrank, 25 deg. of movement, and no more than 2-2.25 in. of elevator chord.
phil Cartier


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