The horizontal surfaces were also rounded, and tailplane incidence was adjustable in flight for trim; the elevators were mounted on a common shaft.
[1][4][5][6] Although Gull variants were powered by five different engines, these were all inverted inline air-cooled types driving two-bladed propellers, making for a neatly faired installation.
The glazed cabin joined smoothly into a raised dorsal fairing, and placed the pilot in front and two passenger seats, slightly staggered behind.
[1] The early models could be fitted with one of two 130 hp (97 kW) 4-cylinder engines, the Cirrus Hermes IV, or the de Havilland Gipsy Major.
Alternatively, for racing or for pilots desiring more power, the 160 hp (119 kW) Napier Javelin III 6-cylinder engine was an option.
The sole Gull Four Mk III (G-ADOE) was used by Blackburn Aircraft as a testbed for both the Cirrus Major Mks 1 and 2 engines.
[9][10] On 4 October 1933 Charles Kingsford Smith started a flight in a Gull Four (G-ACJV), from Lympne Aerodrome to Darwin, Australia, arriving on 10 December 1933, in a record 7 days, 4 hrs, 44 min.
Percival piloted a Gull Six (G-ADEP) from Gravesend to Oran (Algeria), returning to Croydon Airport on the same day, and was later awarded the Oswald Watt Gold Medal in recognition of this flight.
[10][11] On 4 May 1936 Amy Johnson, flying a Gull Six (G-ADZO), flew from Gravesend to Wingfield aerodrome, Cape Town and back to Croydon Airport in a record 7 days 22 hr 43min.
Blackburn Aircraft continued to use its Gull Four Mk III (G-ADOE), later re-engined with a Gipsy Major engine in private ownership.