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Glider release failure?



 
 
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  #1  
Old May 14th 20, 08:35 PM posted to rec.aviation.soaring
Duster[_3_]
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Default Glider release failure?

Has anyone heard of or experienced a case where the pull of the glider's release handle during flight failed to result in the rope dropping off the release mechanism? Last summer two of us were under tow when turbulence threw us too high above the tug (or sink drove the tug too low) @~2,000ft agl. One of us remarked that "We need to release", and we each pulled the handles.. I pulled mine again at least twice and I distinctly remember the cable moving a few cm each time. We turned away from the tug, but after a few seconds I thought I heard a loud bang accompanied by a slight, transient vibration, but no nose movement. Pulled the handle several more times. First I'm thinking we hit the towplane, but then I saw him below and ahead of us with about 4-6' of rope trailing off his Tost release, then radioed him to report the rope break. An inspection did not reveal any evidence that the rope had gotten hung up on the gear doors, wing or empennage. Testing the release gave the normal rope drop after a few mm's of pull, even under heavy tension. The other pilot didn't hear the "break", but the flight logger did record it as a spike of noise on the trace. Any hypotheses on this one?

Perhaps in a related incident, the 2017 Pawnee fatality accident report where there was intra-cockpit video, the glider pilot reported that (after an admitted distraction) he got high on tow, noticed some rope slack, pulled the dive brakes and released the rope. The GoPro showed almost full deployment of the spoilers, first a short movement of the release cable, followed by a "snapping sound", followed by a longer slack in the cable. The report also revealed a short length of rope hanging from the Pawnee (with a high tension break). The NTSB could only conclude that the tug pilot had, for some unknown reason, lost control. Other factors were suggested. The similarity between that incident and ours was that each glider pilot pulled the release handle, assumed the rope fell away but ended up with a rope break. That's my reading of the report, but I may have missed something.
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  #2  
Old May 14th 20, 09:01 PM posted to rec.aviation.soaring
[email protected]
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Default Glider release failure?

glider pilot pulled the release handle, assumed the rope fell away

Why not look to make sure the tow has the whole rope?
It keeps him in site and only takes a second of so.

If there is any doubt that the glider is reliably releasing, then seems like inspecting both the release and logs to see if it is due for rebuild.




  #3  
Old May 15th 20, 01:03 AM posted to rec.aviation.soaring
[email protected]
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Default Glider release failure?

On Thursday, May 14, 2020 at 3:35:18 PM UTC-4, Duster wrote:
Has anyone heard of or experienced a case where the pull of the glider's release handle during flight failed to result in the rope dropping off the release mechanism? Last summer two of us were under tow when turbulence threw us too high above the tug (or sink drove the tug too low) @~2,000ft agl. One of us remarked that "We need to release", and we each pulled the handles. I pulled mine again at least twice and I distinctly remember the cable moving a few cm each time. We turned away from the tug, but after a few seconds I thought I heard a loud bang accompanied by a slight, transient vibration, but no nose movement. Pulled the handle several more times. First I'm thinking we hit the towplane, but then I saw him below and ahead of us with about 4-6' of rope trailing off his Tost release, then radioed him to report the rope break. An inspection did not reveal any evidence that the rope had gotten hung up on the gear doors, wing or empennage. Testing the release gave the normal rope drop after a few mm's of pull, even under heavy tension. The other pilot didn't hear the "break", but the flight logger did record it as a spike of noise on the trace. Any hypotheses on this one?

Perhaps in a related incident, the 2017 Pawnee fatality accident report where there was intra-cockpit video, the glider pilot reported that (after an admitted distraction) he got high on tow, noticed some rope slack, pulled the dive brakes and released the rope. The GoPro showed almost full deployment of the spoilers, first a short movement of the release cable, followed by a "snapping sound", followed by a longer slack in the cable. The report also revealed a short length of rope hanging from the Pawnee (with a high tension break). The NTSB could only conclude that the tug pilot had, for some unknown reason, lost control. Other factors were suggested. The similarity between that incident and ours was that each glider pilot pulled the release handle, assumed the rope fell away but ended up with a rope break. That's my reading of the report, but I may have missed something.


We have seen a couple cases where the ring got hung on the release arm due to slack.
Arms on ships that have low ground clearance have been known to get deformed or have a burr such that this can happen. We just reworked the skid on our 1-34 to get more ground clearance due to this.
It is rare but it can happen.
UH
  #4  
Old May 15th 20, 01:06 AM posted to rec.aviation.soaring
[email protected]
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Default Glider release failure?

On Thursday, May 14, 2020 at 8:03:08 PM UTC-4, wrote:
On Thursday, May 14, 2020 at 3:35:18 PM UTC-4, Duster wrote:
Has anyone heard of or experienced a case where the pull of the glider's release handle during flight failed to result in the rope dropping off the release mechanism? Last summer two of us were under tow when turbulence threw us too high above the tug (or sink drove the tug too low) @~2,000ft agl. One of us remarked that "We need to release", and we each pulled the handles. I pulled mine again at least twice and I distinctly remember the cable moving a few cm each time. We turned away from the tug, but after a few seconds I thought I heard a loud bang accompanied by a slight, transient vibration, but no nose movement. Pulled the handle several more times. First I'm thinking we hit the towplane, but then I saw him below and ahead of us with about 4-6' of rope trailing off his Tost release, then radioed him to report the rope break. An inspection did not reveal any evidence that the rope had gotten hung up on the gear doors, wing or empennage. Testing the release gave the normal rope drop after a few mm's of pull, even under heavy tension. The other pilot didn't hear the "break", but the flight logger did record it as a spike of noise on the trace. Any hypotheses on this one?

Perhaps in a related incident, the 2017 Pawnee fatality accident report where there was intra-cockpit video, the glider pilot reported that (after an admitted distraction) he got high on tow, noticed some rope slack, pulled the dive brakes and released the rope. The GoPro showed almost full deployment of the spoilers, first a short movement of the release cable, followed by a "snapping sound", followed by a longer slack in the cable. The report also revealed a short length of rope hanging from the Pawnee (with a high tension break). The NTSB could only conclude that the tug pilot had, for some unknown reason, lost control. Other factors were suggested. The similarity between that incident and ours was that each glider pilot pulled the release handle, assumed the rope fell away but ended up with a rope break. That's my reading of the report, but I may have missed something.


We have seen a couple cases where the ring got hung on the release arm due to slack.
Arms on ships that have low ground clearance have been known to get deformed or have a burr such that this can happen. We just reworked the skid on our 1-34 to get more ground clearance due to this.
It is rare but it can happen.
UH


I also should have mentioned that a tight tow hook may not open without rope tension, You could pull the release with slack, hook sticks, and release arm closes on hook again.
Good practice would be to hold the release until the rope is confirmed gone..
I'll shut up now.
UH
  #5  
Old May 15th 20, 04:35 AM posted to rec.aviation.soaring
son_of_flubber
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Default Glider release failure?

On Thursday, May 14, 2020 at 3:35:18 PM UTC-4, Duster wrote:
Has anyone heard of or experienced a case where the pull of the glider's release handle during flight failed to result in the rope dropping off the release mechanism?


Does the glider have a Tost release?
  #6  
Old May 15th 20, 04:59 AM posted to rec.aviation.soaring
Marton KSz
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Default Glider release failure?

Witnessed this happening with an SZD-9 Bocian, not being able to release after having been winched to 1000ft. The pilot yanked the release while trying to descend, circling in place. He then asked the passenger in the front seat to pull the release, eventually they got rid of the rope at around 500ft.
  #7  
Old May 15th 20, 05:51 AM posted to rec.aviation.soaring
Frank Whiteley
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Default Glider release failure?

On Thursday, May 14, 2020 at 1:35:18 PM UTC-6, Duster wrote:
Has anyone heard of or experienced a case where the pull of the glider's release handle during flight failed to result in the rope dropping off the release mechanism? Last summer two of us were under tow when turbulence threw us too high above the tug (or sink drove the tug too low) @~2,000ft agl. One of us remarked that "We need to release", and we each pulled the handles. I pulled mine again at least twice and I distinctly remember the cable moving a few cm each time. We turned away from the tug, but after a few seconds I thought I heard a loud bang accompanied by a slight, transient vibration, but no nose movement. Pulled the handle several more times. First I'm thinking we hit the towplane, but then I saw him below and ahead of us with about 4-6' of rope trailing off his Tost release, then radioed him to report the rope break. An inspection did not reveal any evidence that the rope had gotten hung up on the gear doors, wing or empennage. Testing the release gave the normal rope drop after a few mm's of pull, even under heavy tension. The other pilot didn't hear the "break", but the flight logger did record it as a spike of noise on the trace. Any hypotheses on this one?

Perhaps in a related incident, the 2017 Pawnee fatality accident report where there was intra-cockpit video, the glider pilot reported that (after an admitted distraction) he got high on tow, noticed some rope slack, pulled the dive brakes and released the rope. The GoPro showed almost full deployment of the spoilers, first a short movement of the release cable, followed by a "snapping sound", followed by a longer slack in the cable. The report also revealed a short length of rope hanging from the Pawnee (with a high tension break). The NTSB could only conclude that the tug pilot had, for some unknown reason, lost control. Other factors were suggested. The similarity between that incident and ours was that each glider pilot pulled the release handle, assumed the rope fell away but ended up with a rope break. That's my reading of the report, but I may have missed something.


Yes, Open Cirrus CG hook failed to release for several pulls. Tow pilot did not respond to positioning far left and wing rocking nor to radio calls. Eventually released after several pulls from the left position with some slack in the rope. Hook was removed and replaced before next flight after showing excessive play on shaft. Until that aero tow, most launches were from winch while I owned the glider.

Frank Whiteley
  #8  
Old May 15th 20, 11:34 AM posted to rec.aviation.soaring
Hartley Falbaum[_2_]
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Default Glider release failure?

On Thursday, May 14, 2020 at 3:35:18 PM UTC-4, Duster wrote:
Has anyone heard of or experienced a case where the pull of the glider's release handle during flight failed to result in the rope dropping off the release mechanism? Last summer two of us were under tow when turbulence threw us too high above the tug (or sink drove the tug too low) @~2,000ft agl. One of us remarked that "We need to release", and we each pulled the handles. I pulled mine again at least twice and I distinctly remember the cable moving a few cm each time. We turned away from the tug, but after a few seconds I thought I heard a loud bang accompanied by a slight, transient vibration, but no nose movement. Pulled the handle several more times. First I'm thinking we hit the towplane, but then I saw him below and ahead of us with about 4-6' of rope trailing off his Tost release, then radioed him to report the rope break. An inspection did not reveal any evidence that the rope had gotten hung up on the gear doors, wing or empennage. Testing the release gave the normal rope drop after a few mm's of pull, even under heavy tension. The other pilot didn't hear the "break", but the flight logger did record it as a spike of noise on the trace. Any hypotheses on this one?

Perhaps in a related incident, the 2017 Pawnee fatality accident report where there was intra-cockpit video, the glider pilot reported that (after an admitted distraction) he got high on tow, noticed some rope slack, pulled the dive brakes and released the rope. The GoPro showed almost full deployment of the spoilers, first a short movement of the release cable, followed by a "snapping sound", followed by a longer slack in the cable. The report also revealed a short length of rope hanging from the Pawnee (with a high tension break). The NTSB could only conclude that the tug pilot had, for some unknown reason, lost control. Other factors were suggested. The similarity between that incident and ours was that each glider pilot pulled the release handle, assumed the rope fell away but ended up with a rope break. That's my reading of the report, but I may have missed something.


Our Club had a similar sounding event a couple of years ago. Our Pawnee has the TOST reel system. The glider was a ASK 21. The glider pilot was a long retired airline pilot, recently returned to flying. he was solo in the '21, got distracted, and way out of position. He pulled the release, but no release. He did not recall (or maybe know) the Pawnee had the ability to cut the rope. He decided he had to break the rope and tried. He couldn't. The Tug pilot, a multi-thousand hour duster veteran, was about to dump him, when the rope broke. Fortunately, there was enough height and they both recovered. The release was later checked on the ground and found to be OK. Replaced anyway.
Review of ethics's TOST installation manual and other information disclosed that the TOST release force required for an out of position release may be as high as 45 lb at the handle or knob. That is a much higher force than usual.

Hartley Falbaum
  #9  
Old May 15th 20, 04:22 PM posted to rec.aviation.soaring
Tango Whisky
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Default Glider release failure?

Le vendredi 15 mai 2020 14:30:26 UTC+2, waremark a √©crit¬*:
I was at the field when a glider could not release. The combination descended back to the airfield with the rope still attached at both ends and landed safely. I understand that if you want to descend with the rope attached the best way to control the descent is with the glider pilot carefully using the airbrakes.


If you want to land on tow, you descend with full airbrakes into the low tow position and keep the airbrakes fully open. The tow pilot is in charge of the approach/descent. It is essential that on short final, he remembers that there is a glider 5 or 7 meters below him...
That's how we teach this here in Switzerland. It's a quite useless exercise, but it's fun ;-)

  #10  
Old May 15th 20, 05:46 PM posted to rec.aviation.soaring
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Default Glider release failure?

UH: Absolutely relevant, and the suggestion to hold the release open (or cycling once, then hold open) is a good one, particularly if you can't see the rope to confirm as was in our case.
 




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