The G.42 was designed by Gloster to the specification E.1/44 as a
fighter, and was of all-metal construction, except for the
wooden upper fin. It featured a mid-positioned wing, had an
exceptionally broad fuselage and an undercarriage with an
unusually wide track. It was to have four 0.79 in (20 mm)
British Hispano cannons and had provisions made to carry two
bombs or 8 rockets under the wing.
The first prototype (SM809) was completed in July 1947 but was
damaged beyond repair during road transfer to Boscombe Down,
Wiltshire, England, UK, for first flight in August 1947. Building
of the second prototype (TX145) was accelerated and the aircraft made
its first flight from Boscombe Down on March 9, 1948 piloted by
Bill Waterton.
Performance was quite good with a top speed over 600 mph (965
kmh) and a satisfactory rate of climb, but handling qualities
fell short of requirements. To improve the handling qualities
the third prototype (TX148) was fitted with a revised tail
assembly similar to the Meteor F.Mk.8, moving the tail plane
from the fuselage up mid-fin position and this proved very
effective.
The aircraft performance was quite satisfactory but had no
further development potential, so the project was abandoned
with the fourth prototype nearly completed. TX145 and TX148
were used at Farnborough, Hampshire, England, UK, for some years testing
braking-parachutes and flight control systems.