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ACRO E-mail Archive Thread: Pitts S1S Roll Rate


Thread: Pitts S1S Roll Rate

Message: Re: Pitts S1S Roll Rate

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From: Guido Lepore <glepore at>

Date: Wed, 12 Mar 1997 04:43:52 UTC


  I also have Falcon type symmetrical ailerons on my Sparcraft type wings.
Mine have a plywood leading edge (like the wing) but otherwise are
fabric-covered.  Three hinges, and I placed the slave strut as close to the
middle hinge as I could.  I have quite square trailing edges, about 3/8"
thick.  Great stick centering - when you let go of the stick after a
full-deflection roll it snaps back to center and almost vibrates there.
Compared to the stock aileron they go inboard one more bay.  The wings were
squared off at the last rib (the small one  part way into the bow), so the
ailerons don't go outboard any further.  However, because of the
squaring-off, they are full-sized at the outboard end instead of tapering.

Me and my wood-butcher buddies weren't as conscientious as Allan Franko and
there is quite a gap at the aileron bay.  Also, they don't bulge out the
10% into the airsteam that I would have liked.  Stick forces were high, and
I first put big spades on the bottom, and then went to four little spades:
one for each aileron.  Pulling up from 200, 4-5 G gets me about 3 vertical
rolls.  A friend of mine, Greg Howard has basically the same wing and
aileron and yet, like Allan Franko, does not need spades.  Dan Rihn once
told me that he had a garage full of ailerons and he was tired of trying
new ones.  I'm on my fourth set now:  first a S-1C, then the old friese
S-1S, then some really nifty all-aluminum (including the skin .16, all
bonded together by some helicopter techies) ones that didn't survive my
wing loss, and finally these Falcon type.  I should be tired too..... until
I saw the ones that Steve Wolf built for Norm Willis.

These are the same size as mine but have a longer chord, with the hinge
point further back (30% maybe).  At full deflection the extended "nose" of
the aileron pokes into the airstream to balance the load.  Two hinges - the
thinking being that the Pitts wing has a certain amount of flex and twist
under load that is better handled by two hinges instead of three.  Better
roll rate than mine, good neutral and stick centering, light stick forces
and NO SPADES.  Unfortunately, you shouldn't just fit these ailerons onto a
Pitts wing.  Steve was concerned about the load on the rear spar so he
redesigned the wing to have beefier spars to carry the load.  I think Shawn
Tucker uses the same design wing and ailerons.  Like Dick Rihn says,
aileron dabbling can be the road to hell - how many more sets do you want
in your garage?  BTW, Steve Wolf will make you a complete wing like this to
bolt onto an S-1S for a pretty reasonable figure.

Like Franko says though, no question of the improvement to the
competitiveness of a Pitts if you can speed up the roll rate.  You don't
have to fly as fast, so you save energy and altitude.  The roll gets wacked
of quicker on the vertical line leaving more before and after line for the
judges to appreciate, less sag of the top, etc.

Have fun,


© Dr. Günther Eichhorn
Email Guenther Eichhorn