I have prepared a preliminary Why-Because-Analysis of the accident.
It is based mostly on information kindly provided by people on this thread, many thanks for that.
If you've never heard of this method the website about
Why-Because Analysis is highly recommended.
A
PDF file of the analysis of the case is available for download at the
Causalis publications website.
Besides studying the graph I recommend reading the annotations in the provided detailed factor list.
Comments, either private or public, are very welcome.
Bernd