Glider accident while filming commercial in 2011. NTSB Report updated

On Thursday, June 20, 2013 8:07:12 PM UTC-4, Bill D wrote:
There are a bunch of troubling things in this report. I have a lot of ground launch (auto tow) time, but it's a bit dated, so maybe I've forgotten. IIRC, our target speeds were on the order of 50MPH or 55MPH in zero wind, not 70. This was with a Grob and 2-33, but I can't imagine that 70 is right.



---------------------------



From the DG1000 flight manual:

"Recommended winch launch airspeed 110-130 km/h (60-70 kts.)."



Theoretically, the best airspeed for winch launch is that which give the angle of attack for best L/D. With the extra wing loading due to the rope pull, it would certainly be in the 60 - 70 knot range.

Right... but IIRC, the vehicle speed is less (significantly?) than the airpseed when the glider is in the aggressive climb portion of the flight profile. If I read the report correctly, it suggests the tow vehicle was briefed for 70. I have to go dig up the diagram, but the airspeed is the additive of some climb vector involving the secant or arc-tangent or some other function on my old Ti-35 that I no longer remember how to use, no? Like I said, it's been 25 years since I was doing 3-5 ground launches per day, so I could easily be off base.

With the increased interest in ground launch, I do think it's useful to revisit some of the old rules of thumb that used to be well known. Sure, we need the SOP and manuals (which are still out there), but it seems to me that it's good to review the underlying physics every now and then.

I do lots of winch launching but have never even seen an auto-tow. The report says the rope length was 234 foot. Is that normal or even possible? Using a winch, at my club we get 800 to 1200 foot of launch height from 2,100 feet of winch cable - so launch height is a bit more than one third of the cable length. How on earth could you get to a safe launch height from a 234 foot rope?

Forgive me for teaching granny to suck eggs, but some readers may not have had training or experience in this. As a general comment on ground launch failures, firstly it is vital not to rotate too rapidly and not to be too steep too low. However, once in the full climb at a safe height, if a launch failure occurs, it is vital to lower the nose of the glider rapidly well below a normal glide attitude. If the nose is lowered only to a normal glide attitude after a launch failure in a steep climb, the speed may well have reduced below a safe flying speed, with the potential as here for a stall/spin. It is common to teach a rule of thumb that the nose should be lowered as far below the horizon as it was above the horizon before the launch failure.

Mark Burton, London Gliding Club, UK


On Friday, 21 June 2013 01:53:19 UTC+1, Papa3 wrote:
On Thursday, June 20, 2013 8:07:12 PM UTC-4, Bill D wrote:

There are a bunch of troubling things in this report. I have a lot of ground launch (auto tow) time, but it's a bit dated, so maybe I've forgotten. IIRC, our target speeds were on the order of 50MPH or 55MPH in zero wind, not 70. This was with a Grob and 2-33, but I can't imagine that 70 is right.







---------------------------







From the DG1000 flight manual:



"Recommended winch launch airspeed 110-130 km/h (60-70 kts.)."







Theoretically, the best airspeed for winch launch is that which give the angle of attack for best L/D. With the extra wing loading due to the rope pull, it would certainly be in the 60 - 70 knot range.



Right... but IIRC, the vehicle speed is less (significantly?) than the airpseed when the glider is in the aggressive climb portion of the flight profile. If I read the report correctly, it suggests the tow vehicle was briefed for 70. I have to go dig up the diagram, but the airspeed is the additive of some climb vector involving the secant or arc-tangent or some other function on my old Ti-35 that I no longer remember how to use, no? Like I said, it's been 25 years since I was doing 3-5 ground launches per day, so I could easily be off base.



With the increased interest in ground launch, I do think it's useful to revisit some of the old rules of thumb that used to be well known. Sure, we need the SOP and manuals (which are still out there), but it seems to me that it's good to review the underlying physics every now and then.

On Thursday, June 20, 2013 7:10:16 PM UTC-6, waremark wrote:
I do lots of winch launching but have never even seen an auto-tow. The report says the rope length was 234 foot. Is that normal or even possible?

It's not normal or generally advisable but it's possible. With a rope that short, the launch must be planned so the landing is straight ahead or at least with a minimal heading change.

At the end of a day, I've used two aero tow ropes tied together to auto tow to about 300' AGL then glide across the airport infield to land on the ramp.

Disregard... looks like the whole setup was non-standard, so a lot of the usual rules of thumb go out the door. I hadn't noticed the very short rope for example...

On Thursday, June 20, 2013 8:53:19 PM UTC-4, Papa3 wrote:
On Thursday, June 20, 2013 8:07:12 PM UTC-4, Bill D wrote:

There are a bunch of troubling things in this report. I have a lot of ground launch (auto tow) time, but it's a bit dated, so maybe I've forgotten. IIRC, our target speeds were on the order of 50MPH or 55MPH in zero wind, not 70. This was with a Grob and 2-33, but I can't imagine that 70 is right.







---------------------------







From the DG1000 flight manual:



"Recommended winch launch airspeed 110-130 km/h (60-70 kts.)."







Theoretically, the best airspeed for winch launch is that which give the angle of attack for best L/D. With the extra wing loading due to the rope pull, it would certainly be in the 60 - 70 knot range.



Right... but IIRC, the vehicle speed is less (significantly?) than the airpseed when the glider is in the aggressive climb portion of the flight profile. If I read the report correctly, it suggests the tow vehicle was briefed for 70. I have to go dig up the diagram, but the airspeed is the additive of some climb vector involving the secant or arc-tangent or some other function on my old Ti-35 that I no longer remember how to use, no? Like I said, it's been 25 years since I was doing 3-5 ground launches per day, so I could easily be off base.



With the increased interest in ground launch, I do think it's useful to revisit some of the old rules of thumb that used to be well known. Sure, we need the SOP and manuals (which are still out there), but it seems to me that it's good to review the underlying physics every now and then.

On Thursday, June 20, 2013 8:00:14 PM UTC-6, Papa3 wrote:
Disregard... looks like the whole setup was non-standard, so a lot of the usual rules of thumb go out the door. I hadn't noticed the very short rope for example...

With the increased interest in ground launch, I do think it's useful to revisit some of the old rules of thumb that used to be well known. Sure, we need the SOP and manuals (which are still out there), but it seems to me that it's good to review the underlying physics every now and then.



I would suggest reading George Moores papers on winch launch. George has taken the whole subject of ground launch into the 21st century with a very deep and detailed mathematical analysis. His fresh view of the subject is very welcome. His papers can be read in the files section of the Yahoo group winchengineer and winchdesign.

If you'd like to take a look at my training materials, they can be downloaded as PDF's.

Winch pilot training guide: https://dl.dropboxusercontent.com/u/...20Rev%2017.pdf

Winch training slide show: https://dl.dropboxusercontent.com/u/...20Training.pdf

Airfield operations: https://dl.dropboxusercontent.com/u/...operations.pdf

I just started reviewing your training guide, Bill, and I must say,
"Excellent!" It's time to go fly my glider but I've saved the links and
will review all of your stuff for this evening for the refresher benefit,
though I probably won't be doing another ground launch until next "weekend"
at Roach Dry Lake.

I learned to fly off a winch back in the late 80s at Alice Springs, NT,
Australia (Bond Springs, actually) in a Twin Lark with about a mile of
cable, IIRC. Very exciting stuff and we got away every time!

When Black Forest purchased a winch from the AF Academy, Joe Berger and I
removed the small-block Chevy engine and transmission, extended the frame,
and installed a big-block 454 from a truck donated by Dave Rolley. It was
great fun and we used it during the Women's Soaring Seminar at Westcliffe
back in '92 (I think it was - I'll have to dig out my t-shirt to be
sure...). We also used the winch in the test flying of the first PW-5 to
arrive in those parts. IIRC, the FAA required that all maneuvers intended
to be flown had to be done during the test flying and the owner, being a new
pilot asked Tom Serkowski and I to do the flying. What fun we had!

Unfortunately, there was very little support for the winch and it fell into
disrepair. I recently heard that it had been sold.


"Bill D" wrote in message
...
On Thursday, June 20, 2013 8:00:14 PM UTC-6, Papa3 wrote:
Disregard... looks like the whole setup was non-standard, so a lot of the
usual rules of thumb go out the door. I hadn't noticed the very short
rope for example...

With the increased interest in ground launch, I do think it's useful to
revisit some of the old rules of thumb that used to be well known.
Sure, we need the SOP and manuals (which are still out there), but it
seems to me that it's good to review the underlying physics every now
and then.



I would suggest reading George Moores papers on winch launch. George has
taken the whole subject of ground launch into the 21st century with a very
deep and detailed mathematical analysis. His fresh view of the subject is
very welcome. His papers can be read in the files section of the Yahoo
group winchengineer and winchdesign.

If you'd like to take a look at my training materials, they can be
downloaded as PDF's.

Winch pilot training guide:
https://dl.dropboxusercontent.com/u/...20Rev%2017.pdf

Winch training slide show:
https://dl.dropboxusercontent.com/u/...20Training.pdf

Airfield operations:
https://dl.dropboxusercontent.com/u/...operations.pdf

On Friday, June 21, 2013 9:49:00 AM UTC-6, Dan Marotta wrote:
I just started reviewing your training guide, Bill, and I must say,

"Excellent!"

Thanks for the kind word. My only objective is to promote safe winch launch.

I'm positive that if it's done right, winch launch is far safer than aero tow. Germans suffer one accident on average every 180,000 winch launches while we suffer one every 24,000 aero tows. I know there are cultural differences but, presumably, we're pretty good at aero tow and they're at least as good at winch launch so the comparison is probably valid.

It's natural for familiar things like aero tow to seem safe and unfamiliar things like winch launch to look unsafe but the numbers tell a different story.

In article Bill D writes:

I'm positive that if it's done right, winch launch is far safer than aero t=
ow. Germans suffer one accident on average every 180,000 winch launches wh=
ile we suffer one every 24,000 aero tows. I know there are cultural differ=
ences but, presumably, we're pretty good at aero tow and they're at least a=
s good at winch launch so the comparison is probably valid.

But, what is the severity of these accidents? An article (referenced below)
lists 18 fatal+36 serious injury out of 380 winch launch accidents (14.2 percent).
Aerotow had 1 fatal+2 serious injury out of 103 launch accidents (2.9 percent).

See http://www.soaringsafety.org/ssf-06/articles.html - the articles from
November 2006 report a higher rate of winch accidents than aerotow, and a 7.2
times ratio of winch fatalities vs aerotow once adjusted for number of tows of
each type.

The Feb 2008 column revisits it with few additional numbers.

It's natural for familiar things like aero tow to seem safe and unfamiliar =
things like winch launch to look unsafe but the numbers tell a different st=
ory.

The numbers I found in the November 2006 article appear to favor
aerotow for safety, both in accidents per launch, and in severity of
the accident once it has happened.

Alan

On Saturday, June 22, 2013 1:41:41 AM UTC-6, Alan wrote:
In article Bill D writes:



I'm positive that if it's done right, winch launch is far safer than aero t=

ow. Germans suffer one accident on average every 180,000 winch launches wh=

ile we suffer one every 24,000 aero tows. I know there are cultural differ=

ences but, presumably, we're pretty good at aero tow and they're at least a=

s good at winch launch so the comparison is probably valid.



But, what is the severity of these accidents?

The severity is exactly the same for both aero tow and winch. The German LBU accident statistics are available on-line just as the NTSB data is. I suggest you verify them yourself.

I have no idea where the SSF got their numbers but it may have been the UK since no translations are required. 2011 data shows the UK suffers one accident every 16,000 launches while Germany suffers one every 180,000. German numbers are roughly comparable to the rest of continental Europe. The SSF needs to take another, wider look.

I would venture a guess that we (in the USA) are trained for the most part
in aero tow and are very accustomed to it. Winch launching is a novelty
here whereas in Europe it's much more prevalent and the pilots there are
more familiar with the winch.


"Alan" wrote in message
...
In article Bill D
writes:

I'm positive that if it's done right, winch launch is far safer than aero
t=
ow. Germans suffer one accident on average every 180,000 winch launches
wh=
ile we suffer one every 24,000 aero tows. I know there are cultural
differ=
ences but, presumably, we're pretty good at aero tow and they're at least
a=
s good at winch launch so the comparison is probably valid.

But, what is the severity of these accidents? An article (referenced
below)
lists 18 fatal+36 serious injury out of 380 winch launch accidents (14.2
percent).
Aerotow had 1 fatal+2 serious injury out of 103 launch accidents (2.9
percent).

See http://www.soaringsafety.org/ssf-06/articles.html - the articles
from
November 2006 report a higher rate of winch accidents than aerotow, and a
7.2
times ratio of winch fatalities vs aerotow once adjusted for number of
tows of
each type.

The Feb 2008 column revisits it with few additional numbers.

It's natural for familiar things like aero tow to seem safe and unfamiliar
=
things like winch launch to look unsafe but the numbers tell a different
st=
ory.

The numbers I found in the November 2006 article appear to favor
aerotow for safety, both in accidents per launch, and in severity of
the accident once it has happened.

Alan