Glider accident while filming commercial in 2011. NTSB Report updated

Le jeudi 20 juin 2013 21:53:31 UTC+2, Steve Leonard a écrit*:
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.

It looks like they tried to more or less duplicate an old commercial by Michelin, where you saw an ASK-21 being auto-towed on a frozen lake. The glider went brutally up on a very short rope and released almost immediately. Then the car came to a braking halt just in front of an obstacle, while the glider was flying away. It was to illustrate the grip of a "Drice" winter tire... I can't find it on the web anymore. Some small stills are visible if you google "Michelin Drice" for images, but the links are dead.

No mention of the pilot's previous experience with winch / autotow
launching

KN

At 05:30 21 June 2013, wrote:
Le jeudi 20 juin 2013 21:53:31 UTC+2, Steve Leonard a =E9crit=A0:

http://www.ntsb.gov/aviationquery/br...13X31821&ntsb=
no=3DWPR12FA010&akey=3D1
=20
=20
=20
Happened to be looking through the NTSB Database and saw that they
update=
d the report about a month ago.

It looks like they tried to more or less duplicate an old commercial by
Mic=
helin, where you saw an ASK-21 being auto-towed on a frozen lake. The
glide=
r went brutally up on a very short rope and released almost immediately.
Th=
en the car came to a braking halt just in front of an obstacle, while the
g=
lider was flying away. It was to illustrate the grip of a "Drice" winter
ti=
re... I can't find it on the web anymore. Some small stills are visible
if
=
you google "Michelin Drice" for images, but the links are dead.

Sad event and scary stuff.

Can anyone comment if the "steep nose high attitude" was intentional? Were the previous launches straight line low hops which would seem to be safer? Low hops would keep both the glider and the (very important) automobile in the same camera frame. Could something have occurred in the cockpit which forced a dramatic change in pitch attitude?

Which, to me, points back to the length of the rope (234ft) and the tow car driver stating that "The pilot planned to become airborne and then circle back to the airport to land.". Really? Circle back using a 234ft launch rope? He would have only gotten, what, 100feet high? I would seriously doubt that this experienced of a glider pilot (CFIG) would have announced that he could "circle back" even if he thought he would get 200-300 ft sling shot like launch. If not then it flies in the face of what the driver said.

- John "Speculation" D.

I wish we could see the videos.

Boggs

On Friday, June 21, 2013 8:16:25 AM UTC-6, JohnDeRosa wrote:
Can anyone comment if the "steep nose high attitude" was intentional? Were the previous launches straight line low hops which would seem to be safer? Low hops would keep both the glider and the (very important) automobile in the same camera frame. Could something have occurred in the cockpit which forced a dramatic change in pitch attitude?



Which, to me, points back to the length of the rope (234ft) and the tow car driver stating that "The pilot planned to become airborne and then circle back to the airport to land.". Really? Circle back using a 234ft launch rope? He would have only gotten, what, 100feet high? I would seriously doubt that this experienced of a glider pilot (CFIG) would have announced that he could "circle back" even if he thought he would get 200-300 ft sling shot like launch. If not then it flies in the face of what the driver said.



- John "Speculation" D.

Cle Elum Runway 7/25
Dimensions: 2552 x 40 ft.

With a runway this short, a pilot would have to climb very steeply to get any height at all. I'll guess the Caddy towing a DG1000 would need at least 1000' to reach 70mph and another 500' or so to stop. Add 234' of rope length and that leaves less than 700' of runway for the glider to climb - maybe much less.

OTOH, runways this short are used for winch launch. You could expect at least 1000' AGL launches. But then, the Caddy wouldn't have a leading role.

On Friday, June 21, 2013 7:16:25 AM UTC-7, JohnDeRosa wrote:
Can anyone comment if the "steep nose high attitude" was intentional?

I don't think anyone can say exactly what was intentional, other than the deceased pilot.

I have heard - secondhand - that during the planning of the commercial they had wanted a shot from in front of the SUV looking back at it, with the glider rising suddenly & dramatically above it. Whether that was part of the final plans or whether they were trying to film that scene at the time of the accident is anyone's guess.

Frank - One thing to remember is that we do not _know_ if the pilot initiated the turn, or if it merely appeared so as the first phase of spin entry (i.e. a wing-drop). It is entirely possible the pilot was intending to land straight ahead but experienced an asymmetric stall (again, could've been the cross-wind, or a gust, or mechanical turbulence, or lack of coordinated controls, or whatever - we just don't know). I also don't think the satellite photo/maps show clearly if there are bushes or a fence between the runway and the large field - it is possible the pilot had better information about that than we do.

--Noel

Le vendredi 21 juin 2013 07:30:21 UTC+2, a écrit*:
Le jeudi 20 juin 2013 21:53:31 UTC+2, Steve Leonard a écrit*:

It looks like they tried to more or less duplicate an old commercial by Michelin, where you saw an ASK-21 being auto-towed on a frozen lake. The glider went brutally up on a very short rope and released almost immediately. Then the car came to a braking halt just in front of an obstacle, while the glider was flying away. It was to illustrate the grip of a "Drice" winter tire... I can't find it on the web anymore. Some small stills are visible if you google "Michelin Drice" for images, but the links are dead.

I put a copy of the Michelin ad on YouTube, for comparison purpose: http://youtu.be/Rcc2yKQFW5Q

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.

There are additional documents located in the NTSB Docket including witness statements from the driver, photographs of the broken towrope and a video of the accident scenario.

http://dms.ntsb.gov/pubdms/search/hi...KEN=7351 7888




On Friday, June 21, 2013 12:14:22 PM UTC-5, 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