Cle Elum crash on NTSB

On Oct 27, 9:28*pm, Steve Leonard wrote:
What else about their “intentions” were you hoping the NTSB would
state in a preliminary accident report? *Were you expecting them to
detail the entire planned flight path, launch sequence, acceleration
rate, tow car speed for the climb, film crew briefings? *Not gonna
happen with with the NTSB. *They provided some eye-witness information
which may or may not be misleading, and some facts about the airport,
the registered owner of the plane, etc. *We have been told what their
intentions were. * We have been told they were filming a commercial
for Cadillac. *We have been told they used the vehicle for the ground
launch. *We have been told they planned to tow the DG up with their
rope (which the NTSB reports as 234 feet long, made from 5/16th
nylon. *Although, I suspect it is polypropylene.), do a 180, and land
back the other direction. *As for the rest of the sequence, I was not
there, but am presenting what I believe is a plausible explanation of
how the events may have transpired.

We can assume that the rope was intact after the launch, as the NTSB
report reports the length of the rope, and makes no comments about it
being broken, or rings found in the glider, etc. *They would have
stated the rope was broken it if had been. *So, this does not appear
to be any sort of rope overload, as some were presuming.

The witnesses stated that the takeoff appeared normal. *There is
enough confusing information after this if you start putting the math
to it about distance down the runway, altitude, etc to make one
suspicious of the distance and height observations. *The witnesses
reported that the plane "pitched to a steep nose high attitude." *We
know that at some point in the climb (estimated to be 100 to 125
feet), the rope “slackend”. *Three ways the rope can "slacken". *Tow
vehicle slows down, glider pushes over, or rope disconnects. *They say
the glider continued to ascend to about 200 feet of altitude and
leveled off. *Based on what they say happened next, I believe the rope
disconnected and the pilot pushed over.

In an auto tow launch, you lift off, bring the nose up *a little, get
some altitude, then bring the nose on up. *As you near the top of the
climb, the nose comes back down to pretty close to level. *Watch any
video of a winch launch on YouTube. *Very similar, but on car tow, you
don't accelerate as rapidly. *Depending on how the launch is
conducted, you will be rotating to full climb between 100 and 200
feet. *Unfortunately, if you try for the same profile with a 234 foot
rope as you would with a 2000 foot rope (be rotating to full climb
angle at 100 feet AGL), the rope to hitch angle will likely hit the
"back release" angle at somewhere between 100 and 150 feet AGL. *So,
if you try to fly a "normal" launch profile on a short rope, you will
likely get a low altitude back release, as the pilot in this accident
probably got.

So, here you are, about 100 to 150 or so feet AGL, 35-40 degrees or so
nose up, about right on speed for the climb, and the release does its
backrelease thing. *You are surprised, but put the stick on the
forward stop as you are trained. *The plane keeps going up and keeps
slowing down as you are going over the top. *By the time you go over
the top at about 200 feet or so, and have the nose back down to normal
gliding attitude, your airspeed is pretty well gone. *Do the math to
see how much altitude you will gain in slowing from 60 to 30 knots or
so, no drag losses. *Unless you keep the stick forward to get the nose
well below the normal gliding attitude to get flying speed back (and
give up what precious little altitude you have), you will stall.
Pilot probably came across the top at about two hundred or so feet
after this, less than one g and slower than 1 g stall speed. *He then
likely attempted to initiate the turn, as things were "back to normal,
per the plan." *Meaning, he was near the far end of the runway, at
about 200 feet, ready to turn around. *Trouble is, he was below stall
speed. *Attempted to turn and entered a spin.

As to the max speed the towcar attained, I would be very surprised if
they were attempting other than a "normal" ground launch sequnce, but
with a very short rope. *"Normal" being accelerate the car to flying
speed for the plane plus safety margin (no wind, say 65 MPH or so for
the DG? *Remember, his airspeed would go up as soon as he starts to
climb, and the intention was to climb), hold that speed, drive to near
the end, and stop.

A very sad and tragic accident.

Respectfully,
Steve Leonard


What else about their “intentions” were you hoping the NTSB would
state in a preliminary accident report?

This is precisely the problem with NTSB reports, they don't provide
enough facts to make any conclusion. The final report usually come a
year later and often does not have much more information than the
preliminary reports. So so much for the requests to "wait for the NTSB
report". We waited, and now we need the facts so we can draw our own
conclusions and learn the lessons.
And I am pretty sure that some of the readers know more.

As for the plan to do a 180 to land, there is no mention of it in the
NTSB report, only from Gary's comment. I think this is the key to be
able to categorize this accident as "something went terribly wrong" vs
"someone made a terrible decision" or did not know what they were
doing. There is no much we can do to prevent the "something went
terribly wrong" type of accidnets, but there is much we can do to
prevent the later and learn the lessons. Perhaps someone reading this
will, as a result, think twice before attempting an auto tow with a
short rope on a short runway with limited straight ahead options.
Incidentally, I recently visited such an airport were they attempted
an autolaunch on a short runway, slightly uphill with no straight
ahead option, and quickly learned they will be better off finding a
tow plane.

Ramy

On Oct 28, 10:23*am, Ramy wrote:
On Oct 27, 9:28*pm, Steve Leonard wrote:



What else about their “intentions” were you hoping the NTSB would
state in a preliminary accident report? *Were you expecting them to
detail the entire planned flight path, launch sequence, acceleration
rate, tow car speed for the climb, film crew briefings? *Not gonna
happen with with the NTSB. *They provided some eye-witness information
which may or may not be misleading, and some facts about the airport,
the registered owner of the plane, etc. *We have been told what their
intentions were. * We have been told they were filming a commercial
for Cadillac. *We have been told they used the vehicle for the ground
launch. *We have been told they planned to tow the DG up with their
rope (which the NTSB reports as 234 feet long, made from 5/16th
nylon. *Although, I suspect it is polypropylene.), do a 180, and land
back the other direction. *As for the rest of the sequence, I was not
there, but am presenting what I believe is a plausible explanation of
how the events may have transpired.

We can assume that the rope was intact after the launch, as the NTSB
report reports the length of the rope, and makes no comments about it
being broken, or rings found in the glider, etc. *They would have
stated the rope was broken it if had been. *So, this does not appear
to be any sort of rope overload, as some were presuming.

The witnesses stated that the takeoff appeared normal. *There is
enough confusing information after this if you start putting the math
to it about distance down the runway, altitude, etc to make one
suspicious of the distance and height observations. *The witnesses
reported that the plane "pitched to a steep nose high attitude." *We
know that at some point in the climb (estimated to be 100 to 125
feet), the rope “slackend”. *Three ways the rope can "slacken". *Tow
vehicle slows down, glider pushes over, or rope disconnects. *They say
the glider continued to ascend to about 200 feet of altitude and
leveled off. *Based on what they say happened next, I believe the rope
disconnected and the pilot pushed over.

In an auto tow launch, you lift off, bring the nose up *a little, get
some altitude, then bring the nose on up. *As you near the top of the
climb, the nose comes back down to pretty close to level. *Watch any
video of a winch launch on YouTube. *Very similar, but on car tow, you
don't accelerate as rapidly. *Depending on how the launch is
conducted, you will be rotating to full climb between 100 and 200
feet. *Unfortunately, if you try for the same profile with a 234 foot
rope as you would with a 2000 foot rope (be rotating to full climb
angle at 100 feet AGL), the rope to hitch angle will likely hit the
"back release" angle at somewhere between 100 and 150 feet AGL. *So,
if you try to fly a "normal" launch profile on a short rope, you will
likely get a low altitude back release, as the pilot in this accident
probably got.

So, here you are, about 100 to 150 or so feet AGL, 35-40 degrees or so
nose up, about right on speed for the climb, and the release does its
backrelease thing. *You are surprised, but put the stick on the
forward stop as you are trained. *The plane keeps going up and keeps
slowing down as you are going over the top. *By the time you go over
the top at about 200 feet or so, and have the nose back down to normal
gliding attitude, your airspeed is pretty well gone. *Do the math to
see how much altitude you will gain in slowing from 60 to 30 knots or
so, no drag losses. *Unless you keep the stick forward to get the nose
well below the normal gliding attitude to get flying speed back (and
give up what precious little altitude you have), you will stall.
Pilot probably came across the top at about two hundred or so feet
after this, less than one g and slower than 1 g stall speed. *He then
likely attempted to initiate the turn, as things were "back to normal,
per the plan." *Meaning, he was near the far end of the runway, at
about 200 feet, ready to turn around. *Trouble is, he was below stall
speed. *Attempted to turn and entered a spin.

As to the max speed the towcar attained, I would be very surprised if
they were attempting other than a "normal" ground launch sequnce, but
with a very short rope. *"Normal" being accelerate the car to flying
speed for the plane plus safety margin (no wind, say 65 MPH or so for
the DG? *Remember, his airspeed would go up as soon as he starts to
climb, and the intention was to climb), hold that speed, drive to near
the end, and stop.

A very sad and tragic accident.

Respectfully,
Steve Leonard
What else about their “intentions” were you hoping the NTSB would
state in a preliminary accident report?

This is precisely the problem with NTSB reports, they don't provide
enough facts to make any conclusion. The final report usually come a
year later and often does not have much more information than the
preliminary reports. So so much for the requests to "wait for the NTSB
report". We waited, and now we need the facts so we can draw our own
conclusions and learn the lessons.
And I am pretty sure that some of the readers know more.

As for the plan to do a 180 to land, there is no mention of it in the
NTSB report, only from Gary's comment. I think this is the key to be
able to categorize this accident as "something went terribly wrong" vs
"someone made a terrible decision" or did not know what they were
doing. There is no much we can do to prevent the "something went
terribly wrong" type of accidnets, *but there is much we can do to
prevent the later and learn the lessons. Perhaps someone reading this
will, as a result, *think twice before attempting an auto tow with a
short rope on a short runway with limited straight ahead options.
Incidentally, I recently visited such an airport were they attempted
an autolaunch on a short runway, slightly uphill with no straight
ahead option, and quickly learned they will be better off finding a
tow plane.

Ramy


Ramy,
Being very close to this and in the information stream has not been a
lot of fun. The first glider I ever flew in was this DG1000 and the
pilot was this pilot, Lynn, who became my primary CFIG. I have 50
flights in the glider and soloed in it and my logbook is full of sign-
offs from Lynn who was a very careful pilot and seemed very risk
adverse. As the current president of the club he was part of (and a
CFIG for) I have been copied on most of the information and if there
is a smoking gun I am not aware of it. If this occurred because of a
defect or problem with the glider we won't know until the final NTSB
report comes out. Even when you are close to the details there is a
lot of confusion. I was told several times that the tow row was 1"
nylon 200' long, the NTSB says it was 230' and 5/16". From
eyewitnesses to the accident and to the 4 video feeds that the NTSB
has the rope broke before it released (or was released) from the
glider. Multiple accounts also describe a complete cycle prior to the
accident where the glider was launched and landed ahead of the SUV and
that this was another take. The information from the witness on the
youtube video appears to be describing the previous days shooting in
which the glider was areo-towed so it could be filmed with a
helicopter, and the idea that there was a plan to turn around and land
back I have only seen or heard about here on RAS, although there could
have been such a plan.

This weekend I was talking to a glider pilot who was there that day
and his comment was that this probably will not be an accident where
some mysterious aerodynamic factor or aircraft defect is discovered.
The lesson will most likely be found in so many examples where complex
human factors having nothing to do with aviation influenced highly
skilled and trained professionals to start cutting the margins closer
and closer. The book "Into Thin Air" comes to mind. When I first got
into gliding I was surprised by how many accidents involved high time
pilots, but it seems that at some point pilots stop being scared and
start accepting more risks. Sort of like russian roulette where you
pull the trigger 5 times and start to feel like it isn't very
dangerous after all.

Or, maybe it will turn out that something in the glider broke at the
worst possible moment. In any case, one thing I would change about
the set up going in is: Lynn should not have been the one to get all
the credit, take all the blame, make all the decisions, and fly all
the tasks. That was just too much workload. There should have been
one or two other people making the go/nogo decisions free of ego and
careless of blame or any outcome other than a living pilot at the end
of the day. There was no shortage of people with vast auto tow and
aerodynamic knowledge to choose from.

I hope this doesn't come off as trying to lecture or pontificate, but
after this year and all the accidents, maybe all it comes down to is
trying to increase the margin of safety of every part of flying.

Please fly safe,
Brian