Bouncing Bomb Practice Runs

Hello all

At present im trying to piece together some family history and was wondering if anyone here could help me with something. After talking with my grandparents, the general belief is that one of my relatives was killed taking part in a practice run for the bouncing bomb. It is believed that they were testing a new altimetre system, ones pre dating the system with the lamps and I was wondering if there was a way to find out if this is indeed true.

If anyone here could help I would be very much obliged.

Thank you very much

Ross