[3] The first prototype - Seagull serial PA143 - first took off on 14 July 1948 from Southampton Water, flown by test pilot Mike Lithgow.

[4] The second aircraft - PA147 - flew in September 1949, and was used for carrier trials on HMS Ark Royal later in that year,[4] during which it demonstrated the capability to carry five passengers.

The wings were fitted with slotted flaps and full length leading edge slats and could be folded for compact, ship-board stowage.

[4] In July 1950, a Seagull, flown by Les Colquhoun[7] competing in the Air League Cup Race gained the air-speed record for amphibian aircraft over a 100-kilometre (62 mi) course, by flying at an average speed of 241.9 miles per hour (389.3 km/h).

The undercarriage retracted into bays on either side of the fuselage and could be easily removed, saving 180 kilograms (400 lb) of weight when the aircraft was operating as a pure flying-boat.

[5] The Seagull was also fitted with an arrestor hook for carrier landings; mounting points for JATO rockets were located just above the wheel wells.