Slip slidin' away.

The right hand rudder cable on Angel Paula’s JS-1 was cut through; the rudder then went full left. There is no quick obvious way to get control of the rudder when that happens. The glider was about 3,000 ft. AGL then.

The cable was cut by the sharp end of the S tube through which the cable passes. The end of the S tube is normally flared out, or bell shaped. Some manufacturers also run a plastic tube through the S tube and have the cable routed in the plastic. The JS-1 that Angel bailed out of and a sister ship owned by Barton Tate, also at Moriarty, had S tubes with no plastic tube and no flare on the end. The end was apparently cut with some kind of rotary cutter, probably an abrasive disk and the sharp end that resulted was not dressed smooth. I have cut steel tube this way and the end is so sharp you can almost shave with it. It will cut your flesh quite easily.

That sharp end is at the bottom of the tube where the cable exits and goes forward to an anchor point on a bulkhead. Each time the rudder pedal was pressed forward the sharp end of the steel tube cut into the cable. The cable is made of many small diameter wires bundled together. The sharp end of the steel tube simply cut, over many applications of right pedal, the cable one small strand at a time. Soon there were not enough strands to withstand the tension loads and the remaining strands, probably already nicked a bit, broke under that load. The tension spring on the LH rudder pedal then pulled the rudder to full left deflection.

The rudder did not lock out nor did the cable break, it was cut. The breaking strength of stainless steel 7x19 aircraft cable is 1760 lbs, galvanized is 2,000 lbs. The forward anchor point of the cable would fail before the cable reached its breaking point. The pictures of the wreckage show the forward anchor point to be intact. The glider hit almost level, almost no forward movement; the cable did not break during impact. Pictures do show the cut cable.

Jonkers so much admitted the correctness of this description when they sent Barton Tate new rudder pedals with a plastic tube in the S tube. After Angel’s accident Barton sat in his glider and cycled the rudder pedals from stop to stop, his already frayed cable was cut through even further.
This was a sobering moment for Barton.

I have designed and built and flown a rudder pedal assembly, Genesis prototype and production units, I know the critical design points. Those pedals have proven to be trouble free, they have a flared end and a plastic tube. I have pictures of Angle’s cut cable and Barton’s almost severed cable. I have felt the sharp end of the S tube. There is no other scenario that is viable.

Robert Mudd
Composite Aircraft Repair LLC
Moriarty, New Mexico USA

On Saturday, August 31, 2013 2:46:04 PM UTC-4, wrote:

The cable was cut by the sharp end of the S tube through which the cable passes.
..
..
..
The [ed. S-tube] end was apparently cut with some kind of rotary cutter, probably an abrasive disk and the sharp end that resulted was not dressed smooth.

The sheer incompetence and/or disregard for human life that this implies is appalling.

I agree. This makes me wonder what else was overlooked.

Ramy

On Tuesday, September 3, 2013 6:11:15 PM UTC+2, Ramy wrote:
I agree. This makes me wonder what else was overlooked.



Ramy

That's quite a wild statement! Maybe you want to think that through?

Excellent explanation, Robert. Thanks for clarifying this. Fred

Jonkers so much admitted the correctness of this description when they sent Barton Tate new rudder pedals with a plastic tube in the S tube.

So did Jonkers compensate him for the loss of his very expensive glider or is Angel suing them to get it back? Nice that he survived.

Uncle Fuzzy: Instead of just wondering about the integrity of the 30+ year old cables why not put a new set in? It's not that complicated or expensive a job. With lots of gliders there is a calendar or flight hour limit on the cables anyways.

I recall Derek Piggott writing that the DG-100 rudder locks over and that the Janus does too so a Janus flight was a good way of experiencing the effect with an instructor if you had purchased or were considering purchasing a 100.

My 15B slips very steeply and effectively and behaves well in a full slip but the incident with the JS-1 also had me wondering about what would happen if a cable broke. When I disconnected the left cable at the turnbuckle aft of the pedals in the process of replacing my cables I noticed that the rudder was only deflected about ten degrees by the spring on the side that was still hooked up. Of course this doesn't tell me what it would do with a 50 knot or more airflow over it. Since I frequently fly barefoot I suppose I could do a test in flight by simply grabbing one pedal with my toes and pulling it backwards putting slack in the cable while not touching the other pedal.

On Wednesday, September 4, 2013 1:17:24 AM UTC-7, wrote:
Uncle Fuzzy: Instead of just wondering about the integrity of the 30+ year old cables why not put a new set in? It's not that complicated or expensive a job. With lots of gliders there is a calendar or flight hour limit on the cables anyways.



I recall Derek Piggott writing that the DG-100 rudder locks over and that the Janus does too so a Janus flight was a good way of experiencing the effect with an instructor if you had purchased or were considering purchasing a 100.



My 15B slips very steeply and effectively and behaves well in a full slip but the incident with the JS-1 also had me wondering about what would happen if a cable broke. When I disconnected the left cable at the turnbuckle aft of the pedals in the process of replacing my cables I noticed that the rudder was only deflected about ten degrees by the spring on the side that was still hooked up. Of course this doesn't tell me what it would do with a 50 knot or more airflow over it. Since I frequently fly barefoot I suppose I could do a test in flight by simply grabbing one pedal with my toes and pulling it backwards putting slack in the cable while not touching the other pedal.

The cables are fine. I just like to 'what if' when I have the time, and this was one of those times. I found I can make it go generally where I want, with or without rudder input, with or without aileron input, but I do need ONE of them. Kinda' OBE now that my only 'rating' is "Ballast" (maybe 'honorable ballast'

snip...Since I frequently fly barefoot ...

Not in New Mexico, I'd wager!


wrote in message
...
Uncle Fuzzy: Instead of just wondering about the integrity of the 30+ year
old cables why not put a new set in? It's not that complicated or expensive
a job. With lots of gliders there is a calendar or flight hour limit on the
cables anyways.

I recall Derek Piggott writing that the DG-100 rudder locks over and that
the Janus does too so a Janus flight was a good way of experiencing the
effect with an instructor if you had purchased or were considering
purchasing a 100.

My 15B slips very steeply and effectively and behaves well in a full slip
but the incident with the JS-1 also had me wondering about what would happen
if a cable broke. When I disconnected the left cable at the turnbuckle aft
of the pedals in the process of replacing my cables I noticed that the
rudder was only deflected about ten degrees by the spring on the side that
was still hooked up. Of course this doesn't tell me what it would do with a
50 knot or more airflow over it. Since I frequently fly barefoot I suppose I
could do a test in flight by simply grabbing one pedal with my toes and
pulling it backwards putting slack in the cable while not touching the other
pedal.

On Wednesday, September 4, 2013 7:54:47 AM UTC-6, Dan Marotta wrote:
snip...Since I frequently fly barefoot ...



Not in New Mexico, I'd wager!





wrote in message

...

Uncle Fuzzy: Instead of just wondering about the integrity of the 30+ year

old cables why not put a new set in? It's not that complicated or expensive

a job. With lots of gliders there is a calendar or flight hour limit on the

cables anyways.



I recall Derek Piggott writing that the DG-100 rudder locks over and that

the Janus does too so a Janus flight was a good way of experiencing the

effect with an instructor if you had purchased or were considering

purchasing a 100.



My 15B slips very steeply and effectively and behaves well in a full slip

but the incident with the JS-1 also had me wondering about what would happen

if a cable broke. When I disconnected the left cable at the turnbuckle aft

of the pedals in the process of replacing my cables I noticed that the

rudder was only deflected about ten degrees by the spring on the side that

was still hooked up. Of course this doesn't tell me what it would do with a

50 knot or more airflow over it. Since I frequently fly barefoot I suppose I

could do a test in flight by simply grabbing one pedal with my toes and

pulling it backwards putting slack in the cable while not touching the other

pedal.

No barefooting at our glider port in Colorado, nor sandals. The little ball cactus are buggers and it's not rare to have someone hooking up the CG hook during winch launching kneel on one. They hide in the buffalo grass. It's been about five years since a visiting CAP member managed to get bit by a rattler, but he was tempting fate also.

Frank Whiteley