Re: ATR-42/72 in icing

From: (Richard Shevell)
Organization: Stanford University, Dept. of Aero/Astro
Date:         21 Nov 94 13:18:58 
References:   1
Followups:    1
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In article <airliners.1994.1713@ohare.Chicago.COM>, David Lednicer
<> wrote:

> 	My suspicion is that as the balance horns ice, a change in 
> aileron hinge moments is produced, and hence, control load.  However, 
> being ailerons, the change is probably symmetric.  If the horns don't ice 
> symmetrically or one side sheds it ice and the other doesn't, the 
> imbalance in control loads will cause an uncommanded aileron deflection.

Dave, I think you are on to something there.  My first reaction was to
think you were in a time warp talking about balance horns.  That was a
normal design procedure in the 20's and 30's.  Even the DC-3 did not use
horns.  Aerodynamically balanced control surfaces on transports from then
on used an overhang ahead of the hinge line for balance but always
sheltered the overhang in the wake of the fixed surface.  But I found a
drawing of the ATR 72 in Jane's and they do use a horn.  I never worked
with horns but they sure look like ice catchers. In addition to changing
the hinge moment, is there not a possibility of jamming the control. Limit
your ATR-42,-72 flights to the summertime.

Richard Shevell