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ACRO E-mail Archive Thread: [Acro] Re: Pitts rigging

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ACRO E-mail Archive Thread: [Acro] Re: Pitts rigging



                


Thread: [Acro] Re: Pitts rigging

Message: [Acro] Re: Pitts rigging

Follow-Up To: ACRO Email list (for List Members only)

From: "Peter Ashwood-Smith" <petera at nortelnetworks.com>

Date: Tue, 26 Aug 2003 03:11:34 UTC


Message:


Ok here is some documentation I have with my T on rigging the Pitts. I
believe it is from Aviat.

#1 Rigging is the process to get the aircraft flying wings level holding the
stick centered. Ailerons are held in trail maintaining heading with rudder.
The angle of bank is noted for correction. 45 degrees is 6 washers, 20
degrees 2 washers. Either add washers to "drooping wing" I-strut, lower aft
attach point. Or remove washers from opposite side (removal is preferred).
Note: Trailed Ailerons; inboard trailing edge of ailerons matching trailing
edge of wing.

#2 Rolling: (Not wing heavy). After rigging is correct with wings level
release control stick check roll to a known angle i.e. 45 degrees or 30
degrees etc. Time roll to the known angle. Divide angle by time in seconds.
45 degrees by 5 seconds = 9 degree aileron tab bend. This is the beginning
angle of the aileron tab. Aileron tab should be installed on the bottom of
bottom aileron opposite to roll direction. To fly aileron up, tab bend must
be bent down only.
Washers under spades are not acceptable. (Washers will break spades).
The best method of finding what needs to be corrected is to fly the aircraft
in cruise power and check the rigging first. Trail the ailerons and maintain
heading with rudder. The angle of bank will be stable at some angle. Listed
above are a couple of angles and the correction for each.

#3 Stall Break: After rig adjustment has been corrected and plane flies
level with ailerons in trail the next is to check the stall. Deceleration
rate is 1mph per second. Pay special attention to what is done with the
rudders. Check for wing drop at stall. Some stall adjustment can be
corrected at the time of a rig change. The bottom wing is the final stall
wing. A wing drop of about 20 degrees at stall is a 1 washer adjustment.
Preferred location is to install a washer on the top rear I-strut on the
side stall break occurs (to decrease angle of attack). At this time verify
each flight rig, correct if necessary.

Note: No more than 6-AN960 washers at any location are permitted. Washers in
front I-strut position are not recommended.

... Further in the rigging instructions they talk about trailing the
ailerons upper and lower so that they are perfectly matched to the trailing
edge of the wing.

Anyway I guess a quick summary is that you only put washers in the upper or
lower rear I struts. The upper I strut washers are used to decrease angle of
attack on the upper wing and fix stall break problems. The lower I strut
washers are used to correct roll.

There are three other pages on wire tension and how to get a flat upper wing
etc. 

Part of the problem seems to be that as you add and remove washers, the
tensions change and you then have to go back and adjust the tensions to keep
the top wing flat, the proper lower wing dihedral, and proper aileron
trail.... So I guess you have to cycle your way through the process a bit at
a time.

Anyway, I've never had to do this. Mike Mays did mine a few years ago and it
still flies pretty much straight as an arrow ... Unless I touch the controls
then it goes all over the place ;)

Peter

-----Original Message-----
From: Paul B. Stambaugh [mailto:pstambau at yahoo.com] 
Sent: Monday, August 25, 2003 9:36 PM
To: Ashwood-Smith, Peter [CAR:1A00:EXCH]
Subject: Re: [Acro] Re: Pitts rigging


FYI...
I too had my ailerons trainling perfectly and was
informed that the top ailerons need to stick up about
1/4" when the bottom are trailing perfectly.

P


--- Peter Ashwood-Smith <petera at nortelnetworks.com>
wrote:
>  
> Its probably a good idea to take the spades off
> before you start mucking
> about to remove them as possible causes. Also make
> sure the ailerons are
> trailing perfectly and then remove the aileron trim
> tab. Make sure the
> rudder spring tension is equal both at the pedals
> and on the Maule or
> whatever tail wheel i.e. lift the tail wheel off the
> ground make sure the
> rudder is perfectly straight.
>  
> 10 washers sounds like a lot. I believe Aviat says
> no more than 6 Washers in
> any one place, at least for the S-1T. Sparcraft
> wings may have different
> limits on the amount of twist you can safely
> introduce with washers.
>  
> There was a good article on rigging a Pitts in a
> very recent Sport
> Aerobatics magazine. Aviat also has a good sheet on
> the process and the IAC
> technical tips volumes cover it also.
>  
> Cheers,
>  
> Peter
>  
> ----- Original Message -----
> 
> From: Andy Hawes <mailto:ahawes117503 at comcast.net>
> To: Acro Exploder <mailto:acro at gf24.de>  
> Sent: Saturday, August 23, 2003 12:03 AM
> Subject: [Acro] Pitts rigging
> 
> Hello fellow Pitts riggers  --
>  
> I am trying to take care of a fairly decent left
> roll tendency in my Pitts
> S1S.  I need about a quarter inch aileron deflection
> to stop the roll and
> keep the plane level.  I have just tried washing out
> the upper right wing
> with two washers just under the wing in between the
> rear right wing spar and
> the I strut.  This doesn't appear to have helped at
> all.  Maybe just a
> little.
>  
> The left wing leading edge already has several (10)
> washers between the top
> of the I strut and the bottom of the wing.
>  
> I know I need either less lift on the right side, or
> more lift on the left.
> The left appears to be pretty maxed out, with the
> right side now holding 6
> washers in the rear -- hopefully providing more wash
> out?  I'm not sure
> "wash out" is the right term here, less angle of
> attack perhaps?
>  
> Is there anyone who has any suggestions here?  Any
> past email threads or
> articles I might be able to look at?
>  
> Thanks very much,
>  
> Andy Hawes
> 
> 


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