Replacing TOST release at 10K activations

Those of you with TOST hooks, how do you track the number of times the release is activated? As I understand it, the mechanism has to be rebuilt when it's been exercised 10,000 times due to the main spring getting worn out.

Pretty sure it's in the manual.
(Not sure if it's manual for hook or glider!)

For a club glider assumption is 4 activations per launch, once to hook on
to tow to launchpoint, once to release when at launchpoint, once at start
of launch, once at top of launch.

So hook should be overhauled every 2500 launches or so.

Overhaul of our hooks normally costs 150-200 Euro, so about 0.16 Euro a
launch (2-hooks)

If you don't tow the glider around on the hooks you may be able to make a
case for only 2 activations per launch so saving yourself the vast sum of
0.08 per launch

KN


At 16:23 28 January 2014, 150flivver wrote:
Those of you with TOST hooks, how do you track the number of times the
release is activated? As I understand it, the mechanism has to be
rebuilt
when it's been exercised 10,000 times due to the main spring getting worn
out.

Another reason why I don't "check" the release before takeoff. I checked it
when I opened and closed it during hookup and will check it again at the top
of the launch. Checking it again before takeoff will probably be the last
time it functions properly and it will fail during the launch and I'll have
to land on tow (because the tug's release will also fail that day). At
today's rate, that's a savings of $1.09/launch!


"Kevin Neave" wrote in message
...
Pretty sure it's in the manual.
(Not sure if it's manual for hook or glider!)

For a club glider assumption is 4 activations per launch, once to hook on
to tow to launchpoint, once to release when at launchpoint, once at start
of launch, once at top of launch.

So hook should be overhauled every 2500 launches or so.

Overhaul of our hooks normally costs 150-200 Euro, so about 0.16 Euro a
launch (2-hooks)

If you don't tow the glider around on the hooks you may be able to make a
case for only 2 activations per launch so saving yourself the vast sum of
0.08 per launch

KN


At 16:23 28 January 2014, 150flivver wrote:
Those of you with TOST hooks, how do you track the number of times the
release is activated? As I understand it, the mechanism has to be
rebuilt
when it's been exercised 10,000 times due to the main spring getting worn
out.

On Tuesday, January 28, 2014 9:23:47 AM UTC-7, 150flivver wrote:
Those of you with TOST hooks, how do you track the number of times the release is activated? As I understand it, the mechanism has to be rebuilt when it's been exercised 10,000 times due to the main spring getting worn out..

Most Flight Manuals will defer to the Manufacturers recommendation for a particular component (Look at your seatbelts). You understand correctly that it is 10,000 actuation,s or 2000 launches (which most of us will never get to) . The manufacturer also recommends the release be sent in every 4 years.. There is also an Advisory Circular that addresses this. Many of the well known glider maintenance shops in the US like to see no more than 10 years in service before replacement. I tend to agree with this. In many ships they are a pain to get to and do not get cleaned or lubed very often. Also, there is some preload on the main spring so frequent service/replacement is not a bad call. I just bought a late model ship with less than 200 flights on it and I am in the process of replacing all the life limit parts. The release (CG only) was packed with dirt and corroded. While exchanging the release I also had access to the forward gear pivot which is another area that is not usually serviced due to the difficult access. Keep track of your cycles but also take a good look at the release every chance you get.

We've used Tost's previous recommendation to overhaul at 2,000 launches as
a guide and have put this in our maintenance program. We've had a spring
failure on a release that inadvertently did 2,300 launches.

On Tuesday, January 28, 2014 9:16:06 AM UTC-8, Dan Marotta wrote:
...Checking it again before takeoff will probably be the last
time it functions properly and it will fail during the launch and I'll have
to land on tow ...

Dan, the vast majority of Tost E85 nose hook failures are caused by failure of the torsion spring that keeps the hook closed. The result is that the hook will open just fine, it just won't close properly.

Thanks, Bob K.

So, what's the real test, Bob? Would simply giving it a good tug after
hookup disclose a failure? Or would it simply not close over the ring, once
installed by the wing runner? I have only a CG hook - wouldn't it suffer
the same failure mode?


"Bob Kuykendall" wrote in message
...
On Tuesday, January 28, 2014 9:16:06 AM UTC-8, Dan Marotta wrote:
...Checking it again before takeoff will probably be the last
time it functions properly and it will fail during the launch and I'll
have
to land on tow ...

Dan, the vast majority of Tost E85 nose hook failures are caused by
failure of the torsion spring that keeps the hook closed. The result is
that the hook will open just fine, it just won't close properly.

Thanks, Bob K.

On Wednesday, January 29, 2014 3:36:56 PM UTC-8, Dan Marotta wrote:

So, what's the real test, Bob? Would simply giving it a good tug after
hookup disclose a failure? Or would it simply not close over the ring, once
installed by the wing runner? I have only a CG hook - wouldn't it suffer
the same failure mode?

I'm sorry, I don't know the answer to that one.

The one failure I was directly involved with was where one side of the spring had broken, but the other side was intact. The result was that the hook appeared to function correctly, but it sprung open as soon as the towplane powered up. JJ can probably tell you more about this.

Bob K.

In article 150flivver writes:
Those of you with TOST hooks, how do you track the number of times the
release is activated? As I understand it, the mechanism has to be rebuilt
when it's been exercised 10,000 times due to the main spring getting worn
out.

Somewhat in jest, one is tempted to ask if hooking the release handle out
when you release, so it stays pulled until you are ready to hook up next time
would save the operating cycle of the spring.

I doubt it, but it does seem like a rather severely limited lifetime. They
should be using better parts to make their releases last longer - a lot longer.

If I thought that a component in my car (say a spring in the brake system)
had that sort of limited lifetime, I would have bought a different car.

Alan

On Wednesday, January 29, 2014 6:17:11 PM UTC-7, Bob Kuykendall wrote:
On Wednesday, January 29, 2014 3:36:56 PM UTC-8, Dan Marotta wrote:



So, what's the real test, Bob? Would simply giving it a good tug after

hookup disclose a failure? Or would it simply not close over the ring, once

installed by the wing runner? I have only a CG hook - wouldn't it suffer

the same failure mode?



I'm sorry, I don't know the answer to that one.



The one failure I was directly involved with was where one side of the spring had broken, but the other side was intact. The result was that the hook appeared to function correctly, but it sprung open as soon as the towplane powered up. JJ can probably tell you more about this.



Bob K.

Same thing on CG hook, at least with two up. Pull on rope was not enough for the release to open. On another CG hook, release failure, but this was attributed to wear on one of the shafts. CG hooks get a lot of dirt, water (in come regions), and probably an annual cleaning.

Frank W.