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