Heading change
I had another look at this data which was posted earlier:
http://www.zerohedge.com/sites/default/files/images/user5/imageroot/2015/03/rapid%20descent.jpg
It shows that the descent phase started immediately after the completion of a heading change. Also, there is a vertical speed anomaly in the data that coincides with the start of the heading change.
I have read that this turn to 26 degrees heading was part of the flight plan, is that correct? Seems like quite a coincidence that the chain of events would start at the exact same time as the turn. Can anyone speculate how they might be connected?