On Monday, April 16, 2018 at 3:36:42 AM UTC-4, wrote:
There's one in our club and it passed the inspection. Actually I would be interested to know if any 55's except the accident glider have had the opening on top of the fin enlarged as it did. I'm amazed that even one glider had been hacked away at in that manner.

From the AAIB report: "...One other SZD-55-1 glider in the UK fleet inspected by the AAIB, also appeared to have a marginally enlarged elevator slot, of which the owners were unaware. These findings indicate the possibility that such modifications may have historically been considered acceptable among glider owners...".