 The first updated Mk . V sets arrived in April 1942 and were fitted to the de Havilland Mosquito as they became available . A Mk . V equipped Mosquito claimed its first kill on 24 / 25 June , when a Mosquito <unk> from No. 151 Squadron shot down a Dornier Do <unk> @-@ 4 over the North Sea . In practice it was found that pilots had considerable difficulty looking up from the display at the last minute , and the system was used only experimentally . By this time the microwave units had started to arrive in small numbers , so Mk . V production was repeatedly delayed pending their arrival , and eventually cancelled . 
