As difficult as it is to watch, the recent video on the OZ Report of the accident in Khazakstan is insightful. It's clear to me that the initial problems encountered by the pilot just after launch are nothing more than Pilot Induced Oscillations (PIO) caused by the pilots unfamiliarity with the glider and it's levels of stability. This is a very good example of what PIO looks like. The ever-increasing amplitude of roll oscillations are due to the pilots attempts to correct them.
The catastrophic dive that results is more questionable, however, and could be a result of a pitch stability problem with the glider. I suspect we will never know for sure. There are at least reports of the nose cone missing and a recent re-assembly after shipping the glider.
Modifying batten shapes and modified sprog or washout angles is one way to seriously affect the pitch stability of a glider. Always consult with the manufacturer before making these types of changes.
Video of fatality in Khazakstan
Joe is likely right on this, but I have a small bit of input on it. Many years ago, I watched a glider launch from a ramp on the east coast. The glider immediately did exactly what this one did. The pilot managed to get his chute out and landed safely in the trees. Lots of trees.
It turned out that the pilot had assembled his glider, then decided to make a change. He undid the (short) kinkpost on his glider to make the adjustment, then closed the glider without re-attatching the kingpost. This caused the glider to be roll unstable. Or at least more so than he was able to handle. The glider was a Pro-Air Dawn. The problem wasn't the glider, of course, but the "I already preflighted so I don't have to check" mental attitude. He had made a change, so a FULL preflight was now indicated again. It should be noted that the short internal kindpost on this glider could not be seen without opening the sail, so after the sail was closed, none of the wire assist crew could see the problem.
Preflight!!!! If you aren't sure if you have done so, then do it again. And as for the chute - When in doubt, whip it out!
It turned out that the pilot had assembled his glider, then decided to make a change. He undid the (short) kinkpost on his glider to make the adjustment, then closed the glider without re-attatching the kingpost. This caused the glider to be roll unstable. Or at least more so than he was able to handle. The glider was a Pro-Air Dawn. The problem wasn't the glider, of course, but the "I already preflighted so I don't have to check" mental attitude. He had made a change, so a FULL preflight was now indicated again. It should be noted that the short internal kindpost on this glider could not be seen without opening the sail, so after the sail was closed, none of the wire assist crew could see the problem.
Preflight!!!! If you aren't sure if you have done so, then do it again. And as for the chute - When in doubt, whip it out!
Fly High; Fly Far; Fly Safe -- George
Here's the video:
http://www.youtube.com/watch?v=RIV4aZj8aC8
Here's the Oz Report Forum thread, with many contribuitions to understanding:
http://ozreport.com/forum/viewtopic.php?t=5065
http://www.youtube.com/watch?v=RIV4aZj8aC8
Here's the Oz Report Forum thread, with many contribuitions to understanding:
http://ozreport.com/forum/viewtopic.php?t=5065