 During the early years of the war, Welsh acted as a test pilot and became one of the first pilots to fly a plane off an early carrier, flying a Sopwith Schneider floatplane off , while sailing at approximately 18 knots, on 6 August 1915.He again repeated this on 3 November with the ship sailing at full speed.Welsh was shot down while flying a Sopwith Baby seaplane, landing only six miles northeast of Dunkirk on 23 April 1917, although he was unhurt in the crash.