What could cause extremely high effort to release a Tost CG hook on aTwin Astir?

Check for the seat pan binding the cable. Look for witness marks on the
under side of the seat pan.

Good luck!

On 5/31/2015 8:12 PM, Bill D wrote:
On Sunday, May 31, 2015 at 7:58:26 PM UTC-6, Frank Whiteley wrote:
On Sunday, May 31, 2015 at 7:02:37 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 6:58:47 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 6:43:19 PM UTC-6, Bill T wrote:
I believe I remeber a Kestral that had a "stiff release" issue. He removed the seat pan and discovered that the pan was depressing with his weight in it and binding the cable. But you said you have removed the seat pans and checked all of the cables.

My second guess would have been that there was a worn spot or nick in the "jaws" of the TOST release that might be catching on the ring under strain. But you said the TOST was fairly new. Is the TOST ring in fairly good shape and not one of the imposters that were on the market a few years back?

It would be great if you could have a cable under load at GS=0 to visually watch the release mechanism, but that is not a safe venture without a lot of precautions in set up.

BillT
Both the CG hook and the ring pair are brand new. My only guess (AKA pure speculation) is an improper (and unrecorded) repair left the whole forward fuselage weak so it is deforming under winch launch loads causing the yellow-ball to CG hook cable system to bind. FWIW, I do not suspect the hook itself.

Bill D
FWIW, CS-22 regs say a CG hook operating force can't exceed 140N (31.5 Lbs-F) I'm guessing this one takes 200 Lbs-F or more.
Has this changed since winch testing and training started, or remained consistent?

Frank W
No change.

--
Dan Marotta

On Sunday, May 31, 2015 at 8:22:40 PM UTC-6, Dan Marotta wrote:
Check for the seat pan binding the cable.* Look for witness marks on
the under side of the seat pan.



Good luck!




On 5/31/2015 8:12 PM, Bill D wrote:



On Sunday, May 31, 2015 at 7:58:26 PM UTC-6, Frank Whiteley wrote:


On Sunday, May 31, 2015 at 7:02:37 PM UTC-6, Bill D wrote:


On Sunday, May 31, 2015 at 6:58:47 PM UTC-6, Bill D wrote:


On Sunday, May 31, 2015 at 6:43:19 PM UTC-6, Bill T wrote:


I believe I remeber a Kestral that had a "stiff release" issue. He removed the seat pan and discovered that the pan was depressing with his weight in it and binding the cable. But you said you have removed the seat pans and checked all of the cables.

My second guess would have been that there was a worn spot or nick in the "jaws" of the TOST release that might be catching on the ring under strain.. But you said the TOST was fairly new. Is the TOST ring in fairly good shape and not one of the imposters that were on the market a few years back?

It would be great if you could have a cable under load at GS=0 to visually watch the release mechanism, but that is not a safe venture without a lot of precautions in set up.

BillT


Both the CG hook and the ring pair are brand new. My only guess (AKA pure speculation) is an improper (and unrecorded) repair left the whole forward fuselage weak so it is deforming under winch launch loads causing the yellow-ball to CG hook cable system to bind. FWIW, I do not suspect the hook itself.

Bill D


FWIW, CS-22 regs say a CG hook operating force can't exceed 140N (31.5 Lbs-F) I'm guessing this one takes 200 Lbs-F or more.


Has this changed since winch testing and training started, or remained consistent?

Frank W


No change.





--

Dan Marotta

The cable runs are well below the bottom of the seats so it's unlikely they could rub the seat.

On Sunday, May 31, 2015 at 8:05:14 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 7:46:35 PM UTC-6, Frank Whiteley wrote:
On Sunday, May 31, 2015 at 7:02:37 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 6:58:47 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 6:43:19 PM UTC-6, Bill T wrote:
I believe I remeber a Kestral that had a "stiff release" issue. He removed the seat pan and discovered that the pan was depressing with his weight in it and binding the cable. But you said you have removed the seat pans and checked all of the cables.

My second guess would have been that there was a worn spot or nick in the "jaws" of the TOST release that might be catching on the ring under strain. But you said the TOST was fairly new. Is the TOST ring in fairly good shape and not one of the imposters that were on the market a few years back?

It would be great if you could have a cable under load at GS=0 to visually watch the release mechanism, but that is not a safe venture without a lot of precautions in set up.

BillT

Both the CG hook and the ring pair are brand new. My only guess (AKA pure speculation) is an improper (and unrecorded) repair left the whole forward fuselage weak so it is deforming under winch launch loads causing the yellow-ball to CG hook cable system to bind. FWIW, I do not suspect the hook itself.

Bill D

FWIW, CS-22 regs say a CG hook operating force can't exceed 140N (31.5 Lbs-F) I'm guessing this one takes 200 Lbs-F or more.

New hook, correct hook? Correctly installed? Cracked plates? Is replacement of plates logged? Sounds like hook could be rotating under tension but you can't duplicate on ground. Cracked or broken mount plates could perhaps cause this. See these SB's
http://www.ltb-lindner.com/g-103-ad-...ofG%20hook.pdf
http://www.ltb-lindner.com/g-103-ad-...ofG%20hook.pdf

Aircraft log show compliance with both AD's on Apr 6, 2013

But hook was installed since that date? I would verify hook type and visual against the drawings in the above.

Test from front seat also.

Is it a two tow-hook system? Many G-103's removed the CG hook and replaced it with a dummy block. Was the re-installation proper? Look for an obstruction resulting in the nose hook reaching full open and not leaving CG hook sufficient movement to open. Check by removing CG cable (at hook), then actuating release system. Look for improper CG hook, improper installation, not enough cable movement at CG hook.
Hope this helps,
JJ

On Sunday, May 31, 2015 at 7:12:52 PM UTC-7, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.

I'd suggest anchoring the glider, and using a come-along to tension a rope on the hook to some modest value, say ~150 lbs, and actuate the release. That will at least give you an idea of the relationship between tow rope force and actuation force. It will also show you if anything is distorting under tow force.

On Sunday, May 31, 2015 at 10:06:54 PM UTC-6, Frank Whiteley wrote:
On Sunday, May 31, 2015 at 8:05:14 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 7:46:35 PM UTC-6, Frank Whiteley wrote:
On Sunday, May 31, 2015 at 7:02:37 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 6:58:47 PM UTC-6, Bill D wrote:
On Sunday, May 31, 2015 at 6:43:19 PM UTC-6, Bill T wrote:
I believe I remeber a Kestral that had a "stiff release" issue. He removed the seat pan and discovered that the pan was depressing with his weight in it and binding the cable. But you said you have removed the seat pans and checked all of the cables.

My second guess would have been that there was a worn spot or nick in the "jaws" of the TOST release that might be catching on the ring under strain. But you said the TOST was fairly new. Is the TOST ring in fairly good shape and not one of the imposters that were on the market a few years back?

It would be great if you could have a cable under load at GS=0 to visually watch the release mechanism, but that is not a safe venture without a lot of precautions in set up.

BillT

Both the CG hook and the ring pair are brand new. My only guess (AKA pure speculation) is an improper (and unrecorded) repair left the whole forward fuselage weak so it is deforming under winch launch loads causing the yellow-ball to CG hook cable system to bind. FWIW, I do not suspect the hook itself.

Bill D

FWIW, CS-22 regs say a CG hook operating force can't exceed 140N (31.5 Lbs-F) I'm guessing this one takes 200 Lbs-F or more.

New hook, correct hook? Correctly installed? Cracked plates? Is replacement of plates logged? Sounds like hook could be rotating under tension but you can't duplicate on ground. Cracked or broken mount plates could perhaps cause this. See these SB's
http://www.ltb-lindner.com/g-103-ad-...ofG%20hook.pdf
http://www.ltb-lindner.com/g-103-ad-...ofG%20hook.pdf

Aircraft log show compliance with both AD's on Apr 6, 2013

But hook was installed since that date? I would verify hook type and visual against the drawings in the above.

Test from front seat also.

I was told it was but it's sure worth checking.

On Monday, June 1, 2015 at 7:26:07 AM UTC-6, JJ Sinclair wrote:
Is it a two tow-hook system?

Yes



Many G-103's removed the CG hook and replaced it with a dummy block. Was the re-installation proper?

I can't determine that from the maintenance log but it's worth checking.



Look for an obstruction resulting in the nose hook reaching full open and not leaving CG hook sufficient movement to open.

That was my first thought too but I've been lectured that the Twin Astir works differently.

Check by removing CG cable (at hook), then actuating release system. Look for improper CG hook, improper installation, not enough cable movement at CG hook.


Hope this helps,

It helps a lot JJ

On Monday, June 1, 2015 at 8:25:42 AM UTC-6, Bob Kuykendall wrote:
On Sunday, May 31, 2015 at 7:12:52 PM UTC-7, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.

I'd suggest anchoring the glider, and using a come-along to tension a rope on the hook to some modest value, say ~150 lbs, and actuate the release. That will at least give you an idea of the relationship between tow rope force and actuation force. It will also show you if anything is distorting under tow force.

We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.

On Monday, June 1, 2015 at 3:33:14 PM UTC+1, Bill D wrote:
On Monday, June 1, 2015 at 8:25:42 AM UTC-6, Bob Kuykendall wrote:
On Sunday, May 31, 2015 at 7:12:52 PM UTC-7, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.

I'd suggest anchoring the glider, and using a come-along to tension a rope on the hook to some modest value, say ~150 lbs, and actuate the release.. That will at least give you an idea of the relationship between tow rope force and actuation force. It will also show you if anything is distorting under tow force.

We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.

Lay the fuselage on its side??

Perhaps a pulley mounted to a 2 x 12 of sufficient length that the
glider sits on the board to hold it down. Position the glider on the
board to get the desired angle and put a couple of people in the
cockpit. Use a spring scale and come along to set the desired tension.

snip

We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.

--
Dan Marotta