Actual Rope Break

At 23:20 01 June 2014, Kevin Christner wrote:
I had my first "rope break" ever today. I was approximately 200-250ft
abov=
e the ground. Emergency procedures were not a problem.

The Tost released for some reason. Its a nose hook so the back release
mec=
hanism could not have been the culprit. Further testing with the wheel
bre=
ak on the ground revealed no problems so I took another tow and had no
prob=
lems. The ring may not have been engaged properly (doubtful) or the
slack
=
I got in the rope was just too much when it tightened back up (probable
but=
the release still should have held).

In any case has anyone else ever experienced an actual emergency
unplanned
=
release? In 14 years of flying I have never heard of one. Good thing we
d=
o practice this. =20



I fly at a mainly winch launch site but perhaps fortunately originally
learnt to fly at an aero-tow site. A few years ago whilst we had a tug on
site I was giving a first ride in a Duo to a prospective syndicate partner
behind a Super Cub. As we drew level with the winch, at the far end of the
field with perhaps 300 yards of grass before a fairly high hedge, I saw the
unusual sight of the tow rope snaking towards me. I guess our height was
between 150-300 feet. I opted for a 360 degree turn and land on the grass
behind the winch. To his credit my passenger never made a sound till after
we stopped and yes he did buy a share!- The problem? The tug pilot had his
map hanging on the release cord and found it restricted his view so pulled
it off pulling the release in the process! He did buy me a beer that
evening.

Congratulations on a successful outcome Bill!

My only rope break was on my FAA check ride with an inspector in the back seat.

A turbulent tow where the line went slack. A boot full of rudder pre-tension wasn't enough apparently as *snap* a the tow rope became a flicking serpent in front of me. Approx 400ft AGL with limited options in my 12 o'clock I made a turn back and judged I was high. Deviated right of centreline to fly a short base leg to wash off excess altitude before landing. Gained a few points with the examiner that day as he had only just 're-qualifed' on gliders that morning.

In hindsight? I should have been more aggressive in the post-slack yaw to soften the blow a little more. I also feel I could have released the tow rope over the field to allow the FBO to recover the rings instead of 'systematically', soon after PTT.

As a poster in the bunkhouse says, you don't rise to the occasion, you sink to the level of your training. Thanks TK.

On Monday, 2 June 2014 23:41:10 UTC+8, wrote:
Congratulations on a successful outcome Bill!

*ahem*

Kevin

On Monday, June 2, 2014 9:41:10 AM UTC-6, wrote:
Congratulations on a successful outcome Bill!



My only rope break was on my FAA check ride with an inspector in the back seat.



A turbulent tow where the line went slack. A boot full of rudder pre-tension wasn't enough apparently as *snap* a the tow rope became a flicking serpent in front of me. Approx 400ft AGL with limited options in my 12 o'clock I made a turn back and judged I was high. Deviated right of centreline to fly a short base leg to wash off excess altitude before landing. Gained a few points with the examiner that day as he had only just 're-qualifed' on gliders that morning.



In hindsight? I should have been more aggressive in the post-slack yaw to soften the blow a little more. I also feel I could have released the tow rope over the field to allow the FBO to recover the rings instead of 'systematically', soon after PTT.



As a poster in the bunkhouse says, you don't rise to the occasion, you sink to the level of your training. Thanks TK.

My first uncommanded Tost release was on a winch launch at about 10' AGL so I just landed straight ahead on the runway. This was a no-sweat event and I didn't know it was an uncommanded release until the crew told me.

The second was on aero tow just as I decided to release in a good thermal. This was more startling since it seemed like the glider had acquired some intelligence of its own.

The others were during CAP Cadet orientation rides where the Cadet attaching the rope may not have checked the security of the ring in the hook (Our fault since we hadn't trained them to do it). These incidents persuaded us to check the Tost ring pair more carefully for wear and to insist the person attaching the rope checks to insure the ring is free to rattle in the hook.

It's possible for a pilot to detect an improperly inserted ring pair since the yellow knob won't retract all the way if the ring is just "captured" by the "beak". I've learned the hard way to pay attention to how the release knob feels as the hook closes.

I didn't have and actual rope break but had a PTT in 1997. I had about 110 hrs in gliders and was flying an ASW 15B. It was my second flight in that particular glider. The release occured at about 500 ft AGL and I was able to make and abbreviated circuit and land back at the take off Runway 14 at Dansville, NY. Thanks to excellent trainig at the Finger Lkkes Soaring Club, it was not unexpected or very dramatic. The PTT was due to an improper tow ring that someone had put on the tow rope. It was not a Tost Ring Set. I learned to look carefully at the tow ring set before hook up. This resulted in a cleanup of all the improper tow rings in the club. Lets see, 17 years ago, am I due for another one soon? I'm ready!

Chuck Zabinski
N839CZ

On Sunday, June 1, 2014 5:20:14 PM UTC-6, Kevin Christner wrote:
I had my first "rope break" ever today. I was approximately 200-250ft above the ground. Emergency procedures were not a problem.



The Tost released for some reason. Its a nose hook so the back release mechanism could not have been the culprit. Further testing with the wheel break on the ground revealed no problems so I took another tow and had no problems. The ring may not have been engaged properly (doubtful) or the slack I got in the rope was just too much when it tightened back up (probable but the release still should have held).



In any case has anyone else ever experienced an actual emergency unplanned release? In 14 years of flying I have never heard of one. Good thing we do practice this.



2C

I think it's worth inserting in this thread that the Germans suffer essentially zero aero tow PT3 accidents. The US could do the same by strictly observing FAR 91.309, FAR 91.9 and OSHA CFR 1915.112 on rope working strength where life is at risk as well as the Tost specifications on ring pair wear limits. The US and German regulations are essentially the same.

It works like this. Start by using a weak link at the glider as required by the glider flight manual (FAR 91.9) and a weak link 25% stronger at the tug (FAR 91.309) then use a rope 8x as strong as the strongest weak link (CFR 1915.112).

AFAIK, the strongest aero tow weak link called out in a glider manual is 2,436 Lbs-F (LAK-20) so CFR 1915.112 would require a rope with at least 19,500 Lb-F breaking strength. 3/8" Amsteel Blue from Sampson Rope would just meet this requirement. http://www.samsonrope.com/Pages/Prod...?ProductID=872

This rope would be much more expensive than what is commonly used now but it would last much longer - and the lives it would save would be priceless. Rope breaks would be a thing of the past.

A possible argument against Amsteel Blue is its very light weight so rope slack might float above the glider risking entanglement. This could be overcome by using a urethane rope coating as is used on helicopter slings to make the rope heavier and far more abrasion resistant. With a urethane coating, the rope should last decades.

I know someone will point out that a Schweizer hook is limited to 1,200 Lbs-F so it's impossible to comply with 91.9 and 91.309 using this hook. Yep, that's what it means. It IS possible to comply using the Tost tow plane hook.

On Monday, June 2, 2014 4:08:14 PM UTC-5, Bill D wrote:
"I know someone will point out that a Schweizer hook is limited to 1,200 Lbs-F so it's impossible to comply with 91.9 and 91.309 using this hook. Yep, that's what it means. It IS possible to comply using the Tost tow plane hook."

Only flaw in that logic, Bill, is that the HOOK may be approved for that load, but the AIRPLANE it is attached to may NOT be approved for that load. Sort of like how on that old TV show "The Six Million Dollar Man", he could pick up the multi-thousand pound rock with his bionic arm, but they ignored the fact that his still human spine couldn't take the load and he would have been crushed.

I agree with you 100% that there are better things out there than Schweizer tow hitches. But, you can't suddenly legally pull 2000 lbs on the back end of your Cessna or Piper just because your tow hitch is now good for that much load. You have to know where the weakest link is, and either not exceed its limit, or you must increase the strength of it.

As to reliability, I have never known a Schwiezer release to let go of the still intact ring because the ring was worn. I have known of worn Schweizer releases releasing without pilot command, just like a Tost can do if the ring is worn, possibly beyond its allowed limits. So, neither one is perfect. If you have a choice as to which you want to use, make your decision and be willing to listen to the opinions of others.

Interesting that this thread is called "Actual Rope Break" when the rope in question doesn't appear to have broken? :-) We now return to our regularly scheduled programming...

Steve Leonard

On Tuesday, June 3, 2014 8:01:50 AM UTC-6, Steve Leonard wrote:
On Monday, June 2, 2014 4:08:14 PM UTC-5, Bill D wrote:

"I know someone will point out that a Schweizer hook is limited to 1,200 Lbs-F so it's impossible to comply with 91.9 and 91.309 using this hook. Yep, that's what it means. It IS possible to comply using the Tost tow plane hook."



Only flaw in that logic, Bill, is that the HOOK may be approved for that load, but the AIRPLANE it is attached to may NOT be approved for that load. Sort of like how on that old TV show "The Six Million Dollar Man", he could pick up the multi-thousand pound rock with his bionic arm, but they ignored the fact that his still human spine couldn't take the load and he would have been crushed.



I agree with you 100% that there are better things out there than Schweizer tow hitches. But, you can't suddenly legally pull 2000 lbs on the back end of your Cessna or Piper just because your tow hitch is now good for that much load. You have to know where the weakest link is, and either not exceed its limit, or you must increase the strength of it.



As to reliability, I have never known a Schwiezer release to let go of the still intact ring because the ring was worn. I have known of worn Schweizer releases releasing without pilot command, just like a Tost can do if the ring is worn, possibly beyond its allowed limits. So, neither one is perfect. If you have a choice as to which you want to use, make your decision and be willing to listen to the opinions of others.



Interesting that this thread is called "Actual Rope Break" when the rope in question doesn't appear to have broken? :-) We now return to our regularly scheduled programming...



Steve Leonard

Steve, you have a point. My defense is that the installation of a Tost tow plane hook requires an STC which, one presumes, would take aircraft structure into consideration. The Tost Hook itself is approved for 2,570 Lbs-F. If the aircraft structure is weaker, the STC should state a lower limit.

Most composite 2-seater flight manuals (Grob 103, ASK-21 etc...) call out a 600 daN blue weak link for aero tow so the tow plane link would be a red 750 daN link (1,686 Lbs-F) That's more than a Schweizer hook could take but much less than the Tost.

On Tuesday, June 3, 2014 8:01:50 AM UTC-6, Steve Leonard wrote:
On Monday, June 2, 2014 4:08:14 PM UTC-5, Bill D wrote:

"I know someone will point out that a Schweizer hook is limited to 1,200 Lbs-F so it's impossible to comply with 91.9 and 91.309 using this hook. Yep, that's what it means. It IS possible to comply using the Tost tow plane hook."



Only flaw in that logic, Bill, is that the HOOK may be approved for that load, but the AIRPLANE it is attached to may NOT be approved for that load. Sort of like how on that old TV show "The Six Million Dollar Man", he could pick up the multi-thousand pound rock with his bionic arm, but they ignored the fact that his still human spine couldn't take the load and he would have been crushed.



I agree with you 100% that there are better things out there than Schweizer tow hitches. But, you can't suddenly legally pull 2000 lbs on the back end of your Cessna or Piper just because your tow hitch is now good for that much load. You have to know where the weakest link is, and either not exceed its limit, or you must increase the strength of it.



As to reliability, I have never known a Schwiezer release to let go of the still intact ring because the ring was worn. I have known of worn Schweizer releases releasing without pilot command, just like a Tost can do if the ring is worn, possibly beyond its allowed limits. So, neither one is perfect. If you have a choice as to which you want to use, make your decision and be willing to listen to the opinions of others.



Interesting that this thread is called "Actual Rope Break" when the rope in question doesn't appear to have broken? :-) We now return to our regularly scheduled programming...



Steve Leonard

Thinking about this a bit more, a bigger problem is tow planes which are only approved for use with the Schweizer hook. Ex: Cessna 182's. Technically, they are only legal when towing gliders with a 965 Lb-F (439 daN) or less weak link which would exclude composite 2-seaters. FAR 91.9 trumps FAR 91.309 if the glider's Approved flight Manual contains an aero tow weak link specification.

On Sunday, June 1, 2014 7:20:14 PM UTC-4, Kevin Christner wrote:
I had my first "rope break" ever today. I was approximately 200-250ft above the ground. Emergency procedures were not a problem.



The Tost released for some reason. Its a nose hook so the back release mechanism could not have been the culprit. Further testing with the wheel break on the ground revealed no problems so I took another tow and had no problems. The ring may not have been engaged properly (doubtful) or the slack I got in the rope was just too much when it tightened back up (probable but the release still should have held).



In any case has anyone else ever experienced an actual emergency unplanned release? In 14 years of flying I have never heard of one. Good thing we do practice this.



2C

Kevin,

I had my first (and hopefully only) one with full water ballast 200 ft, windy conditions at Perry a couple of years ago. I was the first glider on the grid, and managed to get it back down safely, without running into the other 61 gliders on the grid! The line crew immediately turned me around and launched again, even before I had a chance to clean out my underwear ;-).

Frank (TA)