Pooh Bear wrote:

....
Hence they thought they were flying at 100ft when it was actually 30 ft.
....
They were indeed unaware
of the trees due to the poor briefing material.
....

Being a hard core "look out the window and fly by horizon and feel"
pilot, I have some difficulties to understand this. I'm aware that you
can't fly an airliner by merely looking out the window, but still....

Besides, the briefing material itself wasn't poor. The VAC clearly shows
the forest:

http://www.sia.aviation-civile.gouv....D%202.LFGB.pdf

The "problem" was that the pilot expected to do his show-off over the
runway 20, which has no trees at the far end. When he recognized that
the public was lined up along the glider strip 16, he changed his plans
accordingly and overlooked that this runway was significantly shorter
(i.e. 765 instead of 1120 ft) and there was forest at both ends of the
strip. Which, as I said, I don't understand.

Stefan