A bit of info about the Tomahawk I during testing on its arrival in the UK, the first that underwent testing was BK853 in late 1940. This aircraft had no radios, guns, navigation lights or flame dampening exhausts, but other aspects of testing, such as radiator cooling on the ground were found to be satisfactory. Initially, based on US reports of a tendency to ground loop, testing was done from grass and concrete at Tangmere and the pilots found no difficulty in keeping it straight with the tailwheel interconnected to the rudder.
Gunnery trials were done with AK900 from February 1941 with gun harmonisation, which caused a few issues as there was considerable movement of the barrels and heating of the guns was insufficient. This problem was investigated at length at Duxford. A second aircraft, AK160 acquired for trials found that firing was acceptable but the mounting for the gunsight kept breaking and required strengthening.