left-right play in SGS 1-26 stick?

[son_of_flubber]

I could not find anything relevant on the 1-26 Association's website, and my Google-foo fails me.

I recently flew a rental SGS 1-26C and I'm wondering if anyone can offer information regarding left-right play in the stick. Is this normal, dangerous, fixable?

Measuring at the top of the stick in centered position, the stick freely moves .5-.75" left or right before effecting any change to the aileron position. Total free movement from left to right is 1-1.5". I assume that when holding the stick centered in flight, that the aileron deflects from wind before I feel any feedback at the stick (I have not tested this on the ground). No difficulty encountered flying the plane.

There is no slack travel forwards-backwards on the stick.

The feel reminds me of driving a worn out old car when the steering wheel turns a few degrees before the wheels steer.

Can this be easily fixed? Is it the sum of the looseness in the entire chain of parts controlling the aileron or is it just a stretched control cable?

[Bob Kuykendall]

On Jul 16, 8:47*pm, son_of_flubber > wrote:

> ...Can this be easily fixed? *Is it the sum of the looseness in the entire
> chain of parts controlling the aileron or is it just a stretched control cable?

It is likely to be, as you suggest, the sum of many loose joints. It
is unlikely to be a stretched cable, though it might be a stretched or
bent pulley or bellcrank bracket.

My bet is that the single greatest contributor is the pitch pivot at
the base of the control stick. I think you will find that the holes
for the pivot bolt are elongated, and allow the stick to move a great
deal before engaging the torque tube that runs under the pilot seat.

Thanks, Bob K.

[aerodyne]

>
> My bet is that the single greatest contributor is the pitch pivot at
> the base of the control stick. I think you will find that the holes
> for the pivot bolt are elongated, and allow the stick to move a great
> deal before engaging the torque tube that runs under the pilot seat.
>
> Thanks, Bob K.

I agree with Bob. I believe there is a service bulletin (Not an AD)
to fix this. See the K&L site.

aerodyne

[son_of_flubber]

On Tuesday, July 17, 2012 10:25:27 AM UTC-4, aerodyne wrote:
> >
> > My bet is that the single greatest contributor is the pitch pivot at
> > the base of the control stick. I think you will find that the holes
> > for the pivot bolt are elongated, and allow the stick to move a great
> > deal before engaging the torque tube that runs under the pilot seat.
> >
> > Thanks, Bob K.
>
> I agree with Bob. I believe there is a service bulletin (Not an AD)
> to fix this. See the K&L site.
>

This is a C, the service bulletin is for 1-26 D and E. It concerns the wrong bolt being installed in some ships.

It does state that the expected side-to-side movement is 1/8" not the 1/2" that I observe.

The wierd thing is that the play is only right-left, the elevator control linkage has no play. If the cause is an elongation of a hole, I wonder why the wear is in only one axis.

[Bob Kuykendall]

On Jul 17, 11:23*am, son_of_flubber > wrote:

> ...The wierd thing is that the play is only right-left, the elevator
> control linkage has no play. *If the cause is an elongation of a
> hole, I wonder why the wear is in only one axis.

If you look at how the mechanism works, you'll see that it is not
weird at all. The torque tube decouples pitch and roll inputs so their
levels of free play can be completely different. Pitch inputs move a
short push-pull tube which actuates a walking beam connected to the
two elevator cables. Roll inputs rotate the torque tube under the
seat, which moves a vertical push-pull tube behind the spar; that push-
pull tube actuates a bellcrank that connects to the aileron push-pull
tubes in each wing.

Thanks, Bob K.

[aerodyne]

The service bulletin instructs to contact the factory if play exceeds
1/8".

IIRC, there is a standard repair involving bushings. Call K&L for
disposition.

aerodyne