On Oct 19, 7:49*am, John Cochrane
wrote:
On Oct 18, 10:53*pm, Bill D wrote:









On Oct 18, 6:28*pm, Martin Gregorie
wrote:

On Tue, 18 Oct 2011 06:28:45 -0700, Andy wrote:

As I said in my first answer "if the climb profile was flown correctly".
*Auto tow does not require an aggressive climb profile to reach maximum
altitude as long as the runway length is not limiting. Unlike winch
launching the rope length remains constant.

To me, auto-launching on a 200 ft rope sounds uncomfortably like aero-
towing on a CG hook except that now you're *trying* to get above the
'tug'. This sounds to me like a recipe for getting into the
uncontrollable sling-shot region that upsets tugs. Further, it seems to
me that if you do that to a rear-wheel drive vehicle your problems will
be compounded by a loss of acceleration due to loss of traction as the
rope tension reduces the weight on the driving wheels.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

So, putting this thread together it seems we have another plausible
scenario: the glider does a "ground tow" using a short rope, but
following a climb profile, with the plan being to release and then
land straight ahead. The rope breaks or back-releases with the glider
still pointing up at about 175 feet. *At this point it's nearly
impossible to recover. The glider stalls and spins, resulting in the
nose-down turn reported by the observers. That's a much more common
scenario than spoiler malfunction.

It would seem easy to use a 200 foot rope to just get up to speed,
getting to no more than 50 feet and then overflying the car. Using it
to get altitude, flying a regular climb profile but doing in 200 feet
what you normally do in 1000 feet, could easily lead to the surprise
rope break or back release while still climbing, as the moment to nose
over and release would come very fast and you can't see the car.

I presume those of you who have tried auto towing behind short ropes
(not me!) were basically just getting up to speed, say to do a modern
bungee launch from the top of a hill, not trying to get to the
standard 60 degrees or so maximum altitude release point.

At least it's more plausible than a plan to do a 180 turn from 200
feet!

Presumably at least the NTSB will get to see the video and we will
know what really happened.

John Cochrane

A steep climb on a short rope attached to the CG hook will likely
exceed the weak-link strength (1,000 pounds?) long before you get to
200 feet.

Mike