Grob G-103 Wing Pin Collar Found Disengaged

[George Haeh]

The glider was rigged, hookups checked by another person and flew three flights - off the winch.

The next morning's Daily Inspection found a collar was disengaged.

After some wriggling and pushing we got the collar reengaged.

We've flown this glider for a few years without this happening.

We will be checking every flight for a while.

Have any other G-103 pilots seen this?

[[email protected]]

As I recall, there is a spring that keeps it in the locked position. Best to lock all 4 collars then pull forward on wing tips and re-tighten the forward sleeves, then pull aft on wing tips and re-tighten the aft sleeves. Check all springs inside collars.
JJ

[JohnO[_2_]]

On Tuesday, 4 June 2019 07:03:21 UTC+10, George Haeh wrote:
> The glider was rigged, hookups checked by another person and flew three flights - off the winch.
>
> The next morning's Daily Inspection found a collar was disengaged.
>
> After some wriggling and pushing we got the collar reengaged.
>
> We've flown this glider for a few years without this happening.
>
> We will be checking every flight for a while.
>
> Have any other G-103 pilots seen this?

Yes I have seen the the collar rotate a little after some flying on a few of that type. The retaining system of balls inside the collar do not disengage however the spiral lock to make the system firm backs off. There is a spring in the system to keep some pressure in the lock system.

[[email protected]]

Also, make sure all the balls are in the sleeves. Do this with the wings off, put your finger in the lift fittings and lock the sleeve which will force the balls down. You will be able to feel if a ball is missing. I have found a missing ball on annual inspection.
JJ

[Papa3[_2_]]

Yes we have. I co-own a Grob 103 and taught in several others. Also owned a G102 many years ago. In my experience, I've seen this happen with cyclic fore/aft loading for example if the ship is tied out in windy conditions with some slop in the tiedowns. Also, if folks pull excessively from the wings to maneuver on the ground. As JJ mentions, it's usually possible to get all of the fittings more-or-less equal by loading fore then aft and turning the appropriate collars. There should be some friction in all 4 collars that prevents the pin/collar (there are two different sub-models) from turning without some reasonable force. If one (or more collars) can be turned with minimal force when the other 3 are engaged there is a problem. Either the through-tube is biased toward one side or one of the collars is damaged. See:

http://www.ltb-lindner.com/g-103-ad-sb.html?file=tl_files/ltb_lindner/pdf/G%20103%20LTA%20%26%20TM%20Englisch/315-58%20Wing-fuselage-conection.pdf
http://www.ltb-lindner.com/service-letter.html?file=tl_files/ltb_lindner/pdf/technische%20Infos/SL-11%20%20Wing%20locking%20assemblies.pdf

[[email protected]]

Part of every preflight. Or else.

[George Haeh]

Last winter Lindner issued us a new Flight Manual specifically for our serial.

After your helpful hints, I checked the new manual and found it now contains instructions to pull the wingtips back and forth while hand tightening the collars.

RTFNM