Glider accident while filming commercial in 2011. NTSB Report updated

http://www.gliding.co.uk/bgainfo/saf...hlaunching.htm

It's winch launching, not auto towing, but relevant. Some might find it
useful
and interesting.

the video is heart wrenching. my condolences to friends and family.

I was thinking, the flight is not unlike the second half of a very low pass which has been known to cause another accident in the recent past. Unfortunately done at far too slow of a speed of just 70mph for such a low altitude "pass". Just not enough energy for the pull up and maneuvering back around for landing.

On Friday, June 21, 2013 4:28:39 PM UTC-6, wrote:
the video is heart wrenching. my condolences to friends and family.



I was thinking, the flight is not unlike the second half of a very low pass which has been known to cause another accident in the recent past. Unfortunately done at far too slow of a speed of just 70mph for such a low altitude "pass". Just not enough energy for the pull up and maneuvering back around for landing.

Excellent observation.

On Friday, June 21, 2013 11:14:22 AM UTC-6, Frank Whiteley wrote:
On Thursday, June 20, 2013 1:53:31 PM UTC-6, Steve Leonard wrote:

http://www.ntsb.gov/aviationquery/br...FA010 &akey=1







Happened to be looking through the NTSB Database and saw that they updated the report about a month ago.



Some have said there's nothing new in this report. Indeed there remain some missing details, but there is also a new fact that I don't recall from the prior reports and my inquiries, including discussion with the observer in the back of the launch vehicle.



If the facts are correct, anyone involved in ground launching should have zeroed in on the rope. Nylon rope is very elastic compared to premium UHMWPE ropes, that is, nylon has some 16% elongation at 15% of breaking strength. UHMWPE rope elongation at 30% of breaking strength is under 1%.



Working limits of premium UHMWPE and steel wire ropes are 1/5 to 1/6 of breaking strength. During winch launching we tend to operate beyond these working limits regularly by loading to 1/4 to 1/3 of breaking strength with premium UHMWPE ropes, and presumably as high as 3/5 with the regular UHMWPE and steel wire ropes. For all practical purposes, there is minimal elongation.



Nylon rope's typical working limit is 1/12 of breaking strength. 5/16" nylon rope, as described in the report is rated from about 1490lbs to 3300lbs breaking strength depending on construction and processing. Most constructions are rated in the 1500lb to 2200lb BS range, which would indicate that a DG1000 could easily reach and exceed 1/1 with most nylon ropes and reach 2/3 with the best ropes assuming a black TOST weak link was used. Repeated [over]load cycles will accelerate fatigue and this rope would have been loaded near breaking strength repeatedly over the course of several launches. One can only imagine the elongation near the breaking point. Perhaps they started with a 200ft rope which was stretched to 234ft when it broke. 17% elongation. Breakage without any signs of appreciable wear would be expected within a very few launches. I'm not aware of any glider operations using nylon rope for ground launching. Steel, poly-types, and dacron, yes, but not nylon.



There is a large field off the end of runway 7. If the pilot thought he had enough height to attempt to circle to a landing, he definitely had this field as an option. The remainder of the conjecture would seem that he commenced a turn before resuming flying speed after the break.



Frank Whiteley

Frank, that's all true but it's in the nature of ropes to break. Good ropes break less often than crappy ropes but they still break - that's just how it is. The trick is to never put oneself in a a position where a rope break causes an accident. Good pilots EXPECT the rope to break on every launch and have a plan to deal with it.

The NTSB supplemental data with the witness video clearly shows the pilot did not lower the nose, made no attempt to recover airspeed and (likely) started a turn leading to a stall and spin to impact. Nor does the video show any evidence the pilot made an attempt to stop the spin departure once it had begun.

Google Earth shows a 1400' plowed field off the departure end of runway 7. If this field was useable, the rope break was survivable provided the pilot promptly lowered the nose, recovered airspeed and landed ahead in the field.

To people unfamiliar with winch launching or auto tow the climb angle looks
very steep, and certainly is compared to an aero tow.
234 feet is very short for an auto tow rope and you would not expect the
glider to get more than 200 ft from that.
I have completed 10,000 winch launches and of those about 2000 have been
practice launch failures, about 100 for real. I have done about 200 auto
tow launches where the most common cause of lack of power is lifting the
driving wheels of the tow truck off the ground at the top of the launch.
Folowing a launch failure (rope break/loss of power)nearly all pilots take
the initial recovery automatically, moving the stick forward to adopt a
nose down attitude. This will always introduce negative G which in effect
reduces the wing loading on the glider meaning the stall speed is much
lower than is normally the case. If an attempt to turn is made at this
stage, as the effect of the negative G goes away, a stall may occur and if
aileron is applied and there is any bank a spin is most likely. A DG 1000
is one of the GRP gliders that will spin readily. A full recovery from a
spin at 200 ft is not possible.
This is why we teach the recovery as move the stick forward to adopt at
least the approach attitude AND wait until approach speed is gained. Then
make the decision as to whether you are going to land ahead or turn.

On Friday, June 21, 2013 4:21:55 PM UTC-6, Don Johnstone wrote:

This is why we teach the recovery as move the stick forward to adopt at
least the approach attitude AND wait until approach speed is gained. Then make the decision as to whether you are going to land ahead or turn.
________________________
The math says you will do better to push the nose lower than the approach attitude both in recovering airspeed sooner and retaining as much altitude as possible.

Without the benefit of an angle of attack indicator, the greatest safety margin is to push the nose as far below the horizon as it was above at failure and hold it there until at least the "Yellow Triangle" airspeed is in hand. This "rule of thumb" prevents diving the glider into the runway from a low failure and provides a good margin at higher altitudes.

With an AOA indicator, if you chose, you could gently reload the wings at the top of the trajectory using an AOA equivalent to best L/D which results in the least loss of height. Since angle of attack determines whether the wing will stall, the airspeed at the beginning of the reload can safely be below the normal 1G stalling speed.

Speaking of AOA indicators and stick buzzers, does anyone think one might have saved this pilots life?

On Friday, June 21, 2013 1:49:25 PM UTC-6, Bill D wrote:
On Friday, June 21, 2013 11:14:22 AM UTC-6, Frank Whiteley wrote:

On Thursday, June 20, 2013 1:53:31 PM UTC-6, Steve Leonard wrote:



http://www.ntsb.gov/aviationquery/br...FA010 &akey=1















Happened to be looking through the NTSB Database and saw that they updated the report about a month ago.







Some have said there's nothing new in this report. Indeed there remain some missing details, but there is also a new fact that I don't recall from the prior reports and my inquiries, including discussion with the observer in the back of the launch vehicle.







If the facts are correct, anyone involved in ground launching should have zeroed in on the rope. Nylon rope is very elastic compared to premium UHMWPE ropes, that is, nylon has some 16% elongation at 15% of breaking strength. UHMWPE rope elongation at 30% of breaking strength is under 1%.







Working limits of premium UHMWPE and steel wire ropes are 1/5 to 1/6 of breaking strength. During winch launching we tend to operate beyond these working limits regularly by loading to 1/4 to 1/3 of breaking strength with premium UHMWPE ropes, and presumably as high as 3/5 with the regular UHMWPE and steel wire ropes. For all practical purposes, there is minimal elongation.







Nylon rope's typical working limit is 1/12 of breaking strength. 5/16" nylon rope, as described in the report is rated from about 1490lbs to 3300lbs breaking strength depending on construction and processing. Most constructions are rated in the 1500lb to 2200lb BS range, which would indicate that a DG1000 could easily reach and exceed 1/1 with most nylon ropes and reach 2/3 with the best ropes assuming a black TOST weak link was used. Repeated [over]load cycles will accelerate fatigue and this rope would have been loaded near breaking strength repeatedly over the course of several launches. One can only imagine the elongation near the breaking point. Perhaps they started with a 200ft rope which was stretched to 234ft when it broke. 17% elongation. Breakage without any signs of appreciable wear would be expected within a very few launches. I'm not aware of any glider operations using nylon rope for ground launching. Steel, poly-types, and dacron, yes, but not nylon.







There is a large field off the end of runway 7. If the pilot thought he had enough height to attempt to circle to a landing, he definitely had this field as an option. The remainder of the conjecture would seem that he commenced a turn before resuming flying speed after the break.







Frank Whiteley



Frank, that's all true but it's in the nature of ropes to break. Good ropes break less often than crappy ropes but they still break - that's just how it is. The trick is to never put oneself in a a position where a rope break causes an accident. Good pilots EXPECT the rope to break on every launch and have a plan to deal with it.



The NTSB supplemental data with the witness video clearly shows the pilot did not lower the nose, made no attempt to recover airspeed and (likely) started a turn leading to a stall and spin to impact. Nor does the video show any evidence the pilot made an attempt to stop the spin departure once it had begun.



Google Earth shows a 1400' plowed field off the departure end of runway 7.. If this field was useable, the rope break was survivable provided the pilot promptly lowered the nose, recovered airspeed and landed ahead in the field.

Hard to say from the report images whether the rope had any worry marks, but there are some discolorations in the break area. It appears to be reasonable quality rope, but nylon just is not the right media and is very low working limit for it's breaking strength and diameter. The recoil of the rope in the video is pretty interesting as the bulk of the rope bunches up in a clump only a few fuselage lengths behind the glider. If the rope had previously recoiled toward the release on the car during earlier launches, it's possible it was compromised by impacting the car or release hardware (hence the marks). One witness described seeing 6-8 inches of rope remaining at the car end.

Unfortunately the short out of focus view obscures any chance of seeing control deflections and possible pilot intent.

Ropes may be expected to break, but choice of rope makes a big difference.

Frank Whiteley

At 00:28 22 June 2013, Frank Whiteley wrote:


Hard to say from the report images whether the rope had any worry marks,
bu=
t there are some discolorations in the break area. It appears to be
reason=
able quality rope, but nylon just is not the right media and is very low
wo=
rking limit for it's breaking strength and diameter. The recoil of the
rop=
e in the video is pretty interesting as the bulk of the rope bunches up
in
=
a clump only a few fuselage lengths behind the glider. If the rope had
pre=
viously recoiled toward the release on the car during earlier launches,
it'=
s possible it was compromised by impacting the car or release hardware
(hen=
ce the marks). One witness described seeing 6-8 inches of rope remaining
a=
t the car end.



Ropes may be expected to break, but choice of rope makes a big
difference.

Frank Whiteley

We use skyrope, which is nylon rope on our winch and the failure rate is
much less than with wire rope

On Saturday, June 22, 2013 4:02:59 AM UTC-6, Don Johnstone wrote:
At 00:28 22 June 2013, Frank Whiteley wrote:





Hard to say from the report images whether the rope had any worry marks,

bu=

t there are some discolorations in the break area. It appears to be

reason=

able quality rope, but nylon just is not the right media and is very low

wo=

rking limit for it's breaking strength and diameter. The recoil of the

rop=

e in the video is pretty interesting as the bulk of the rope bunches up

in

=

a clump only a few fuselage lengths behind the glider. If the rope had

pre=

viously recoiled toward the release on the car during earlier launches,

it'=

s possible it was compromised by impacting the car or release hardware

(hen=

ce the marks). One witness described seeing 6-8 inches of rope remaining

a=

t the car end.







Ropes may be expected to break, but choice of rope makes a big

difference.



Frank Whiteley



We use skyrope, which is nylon rope on our winch and the failure rate is

much less than with wire rope



The technical specifications would be more helpful than the hyberbole
http://www.skylaunchuk.com/proddetai...prod=CC-9-1200

Can you point to something more useful about this product?

Frank

On 6/21/2013 1:14 PM, Frank Whiteley wrote:
Some have said there's nothing new in this report.
Indeed there remain some missing details, but there
is also a new fact that I don't recall from the prior reports and
my inquiries, including discussion with the observer in the back of
the launch vehicle.

If the facts are correct, anyone involved in ground launching should have zeroed in on the rope.

And on that previously taped-over damage to the wing leading edge! In
my (very limited) experience with leading edge damage, that's possibly
sufficient to cause a wicked wing drop in a deep stall. So it could
have contributed to the accident, even though the NTSB report didn't
seem to give it much significance.

There is no way that glider was legally airworthy with that unrepaired
wing damage.

See the examination report with pictures he
http://dms.ntsb.gov/pubdms/search/do...9&mkey=8205 9


Or:http://preview.tinyurl.com/m6ul7gq