L-23 Loose Horizontal Stabilizer

[Chris Snyder]

We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything:

https://www.screencast.com/t/iiOd0TSi8zpX

[Tango Eight]

On Tuesday, September 10, 2019 at 1:11:32 PM UTC-4, Chris Snyder wrote:
> We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything:
>
> https://www.screencast.com/t/iiOd0TSi8zpX

Our L-23 would not go together with the pins looking like that. With everything shiny clean and well greased, it is a real chore to wiggle the elevator drive home. There is no play, anywhere, and certainly none that could be noticed from the cockpit.

I think I'd go have a very close look at that elevator and how assembled.....

best,
Evan Ludeman

[Chris Snyder]

On Tuesday, September 10, 2019 at 1:47:25 PM UTC-4, Tango Eight wrote:
> On Tuesday, September 10, 2019 at 1:11:32 PM UTC-4, Chris Snyder wrote:
> > We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything:
> >
> > https://www.screencast.com/t/iiOd0TSi8zpX
>
> Our L-23 would not go together with the pins looking like that. With everything shiny clean and well greased, it is a real chore to wiggle the elevator drive home. There is no play, anywhere, and certainly none that could be noticed from the cockpit.
>
> I think I'd go have a very close look at that elevator and how assembled.....
>
> best,
> Evan Ludeman

That was a "stock photo" I found from an assembly manual, but good to know.

[Bob Kuykendall]

On Tuesday, September 10, 2019 at 10:11:32 AM UTC-7, Chris Snyder wrote:
> We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything...

You should probably take any looseness in the elevator drive or horizontal stabilizer attachment quite seriously.

Can you describe the play more precisely? Is the play in the elevator actuation, or in the horizontal stab attachment?

--Bob K.

[Charles Longley]

I have a lot of experience on L-23 loose horizontal stabs. The first thing I would check is the fit of the pins. The maintenance manual will tell you the exact maximum number. You’ll need to measure the OD on the pins and the ID on the rocker assembly. Stock pins are pretty easy to find, oversized not so much. If you have to oversize you’ll need to ream the rocker assembly.

Clean and plenty of grease when the horizontal gets put on.

[Chris Snyder]

On Tuesday, September 10, 2019 at 2:30:54 PM UTC-4, Bob Kuykendall wrote:
> On Tuesday, September 10, 2019 at 10:11:32 AM UTC-7, Chris Snyder wrote:
> > We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything...
>
> You should probably take any looseness in the elevator drive or horizontal stabilizer attachment quite seriously.
>
> Can you describe the play more precisely? Is the play in the elevator actuation, or in the horizontal stab attachment?
>
> --Bob K.

Word from Blanik America is the MM provides the tolerance for how much movement is acceptable, so we're going to measure that tonight. The play is in the stab attachment. Apparently there are a few sources that can cause this.

[Chris Snyder]

On Tuesday, September 10, 2019 at 2:40:38 PM UTC-4, Charles Longley wrote:
> I have a lot of experience on L-23 loose horizontal stabs. The first thing I would check is the fit of the pins. The maintenance manual will tell you the exact maximum number. You’ll need to measure the OD on the pins and the ID on the rocker assembly. Stock pins are pretty easy to find, oversized not so much. If you have to oversize you’ll need to ream the rocker assembly.
>
> Clean and plenty of grease when the horizontal gets put on.

Thanks for the tip. We'll measure these specs too.

[Frank Whiteley]

On Tuesday, September 10, 2019 at 1:10:45 PM UTC-6, Chris Snyder wrote:
> On Tuesday, September 10, 2019 at 2:30:54 PM UTC-4, Bob Kuykendall wrote:
> > On Tuesday, September 10, 2019 at 10:11:32 AM UTC-7, Chris Snyder wrote:
> > > We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything...
> >
> > You should probably take any looseness in the elevator drive or horizontal stabilizer attachment quite seriously.
> >
> > Can you describe the play more precisely? Is the play in the elevator actuation, or in the horizontal stab attachment?
> >
> > --Bob K.
>
> Word from Blanik America is the MM provides the tolerance for how much movement is acceptable, so we're going to measure that tonight. The play is in the stab attachment. Apparently there are a few sources that can cause this.

Our former L-23 developed play in the horizontal that exceeded the limits. The yoke and pins had to be replaced. The yoke was ordered and arrived without new pins, so they had to be ordered separately. Be sure to order both together if that's the source of the play. Not sure about today, but IIRC it took 4-5 months to get the yoke. The pins, not so long.

Frank Whiteley

[Chris Snyder]

On Tuesday, September 10, 2019 at 6:02:40 PM UTC-4, Frank Whiteley wrote:
> On Tuesday, September 10, 2019 at 1:10:45 PM UTC-6, Chris Snyder wrote:
> > On Tuesday, September 10, 2019 at 2:30:54 PM UTC-4, Bob Kuykendall wrote:
> > > On Tuesday, September 10, 2019 at 10:11:32 AM UTC-7, Chris Snyder wrote:
> > > > We just noticed some play on our club L-23. It was detected in the stick while on tow with a forward CG. Does anyone have experience with a horizontal stab being loose on an L-23? The elevator auto-hookups have large pins, but it seems like there's no way to really tighten anything...
> > >
> > > You should probably take any looseness in the elevator drive or horizontal stabilizer attachment quite seriously.
> > >
> > > Can you describe the play more precisely? Is the play in the elevator actuation, or in the horizontal stab attachment?
> > >
> > > --Bob K.
> >
> > Word from Blanik America is the MM provides the tolerance for how much movement is acceptable, so we're going to measure that tonight. The play is in the stab attachment. Apparently there are a few sources that can cause this.
>
> Our former L-23 developed play in the horizontal that exceeded the limits.. The yoke and pins had to be replaced. The yoke was ordered and arrived without new pins, so they had to be ordered separately. Be sure to order both together if that's the source of the play. Not sure about today, but IIRC it took 4-5 months to get the yoke. The pins, not so long.
>
> Frank Whiteley

Okay, that's good to know. Thankfully our stab measurement was within the specs, so we're good for now.

Thanks everyone for all of the help!