The Supermarine Seagull was a flying boat produced developed by Supermarine’s chief designer R.J. Mitchell, from the experimental Supermarine Seal II in 1920. In June 1921 the Seagull was evaluated but rejected, but was further developed as a private venture. In February 1922 this time it impressed the air ministry which placed an initial order for two aircraft for evaluation. Later production is believed to have assisted Supermarine to survive in its recession and gave Britain the superb spitfire. The Seagull was used by the British Fleet Air Arm mostly for gunnery spotting and reconnaissance. It was operated by the Royal Australian Air Force from its only seaplane carrier HMAS Albatross. When the latter asked for a catapult-capable model, the company developed the Seagull IV which ultimately became the Walrus.

Development

Note: The origin and development of Supermarine as a company can be found here as well as its legendary later chief designer, RJ Mitchell. Supermarine started as a yacht builder in 1913 as Pemberton-Billing. Its fist model, the Pemberton-Billing P.B.1, was not impressive and never flew. The company was sold to Top Sopwith to built its “bat boat” and built Short S.38 seaplanes under licence in 1915. When resold to Hubert Scott-Paine it gained it final name of “Supermarine Aviation Works Ltd” and to boost its communication, started to participate in the 1919 Schneider Trophy contest. While the company won 1922 with the Sea Lion II, its production was miserable, with only the Seal as marketed model to the RNAS.

Supermarine Seal

The Seal was a prototype designed first by R.J. Mitchell, which first flight on May 1921 as a fleet Spotting Gunnery Amphibian. It was based on the Supermarine Commercial Amphibian which achieved second place after it was entered for an Air Ministry competition in 1920. The Seal II was the first British flying boat with the propeller positioned in front of the engine. It was a 450 horsepower (340 kW) Napier Lion water-cooled model, avoiding seawater spray injection. The pilot was seated forward (nose) fuel tanks behind and second cockpit behind the wing for the MG gunner. The hull was profile like a snail and it was not going to take prize for its looks. It was not rejected by the RAF outright and when tested at the Isle of Grain was found satisfactory.

But modifications were asked for, like moving the position of the fuel tanks to the upper wing, increasing the rudder and fin for extra stability in flight and adding a 480 horsepower (360 kW) Napier Lion II. The advantage of this model as being an amphibian was not lost as it combined the advantage of being launched from an aircraft carrier deck or from shore bases, and land anywhere. The Seal could reach 112 mph (180 km/h, 97 kn) and fly over 4 hours at max 10,000 ft.

Supermarine Seagull

Mitchell modified the Seal II which went to two new prototypes to answer specification 21/21. They were ordered by the Air Ministry in early 1922 for further testings. The hull was lenghtened by 2 feet (0.61 m), tail surfaces were increased, the wings were alterned for better balance. N185 and N159 (‘Seagull’) were presented on 4 July 1921 for tests before being delivered to the RAF. One was poresent at the RAF Aerial Pageant at Hendon (June). Mitchell also designed the Fleet Spotting Gunnery Amphibian but it stayed on paper.

The single Seal II and a single Seagull were then sold to the Imperial Japanese Navy Air Service (IJNA), when discivered after a mission in Britain. They were shipped as part of the Sempill Mission to Kasuimiguara, north-east of Tokyo by November 1921 and tried and tested heavily. Meanwhile, On 4 July 1922, Seagull was selected, designated Seagull Mk I and production designation was however “Seagull Mk II” due to the modifications asked for. The two versions were similar bt for the powerplant, now upgraded to the Napier Lion III engine. It also had a reduced wingspan but larger fin. Production was scheduled under the serials N9642–N9647 (so seven in all) in 1922. 25 were built eventually for the Air Ministry and Royal Navy, made in small batches to keeep the company afloat. Supermarine was almost bankrup after building these prototypes.

In 1925, construction of the Mk III started for the Royal Australian Air Force (RAAF), placing an order in January. It was given the Napier Lion V engine and reworked radiators that were “tropicalized”. The RAAF had six Mk IIIs sent between 1926 and 1927 which corresponded the launching of HMAS Albatross, a seaplane carrier equally built to save Cockatoo Yard (Sydney) afloat. In 1928, one Seagull Mk II was rebuilt and redesignated Mk IV with Handley-Page leading edge slots, twin fins and rudders and was reveloped further when accepted into production as the Walrus, arguably most successful seaplane from Supermarine.

Design

General conception

The Supermarine Seagull was an amphibian flying boat powered with a front-mounted Napier Lion engine in a nacelle slung from the upper wing. It drove a four-blade wooden, single pitch propeller, in a tractor configuration whereas many models of seaplanes at the time were pushed to keep the engine as far from seawater as possible. Gravity feed ensured fuel arrived in the injection. Thuis was completed by a large radiator in front of the engine and deflector on either side.

The lower wing had a shoulder location, with two bays. The floats were attached to it near the wingtips, via struts in a positon that maximised buoyancy and reduced drag. The Seagull being an amphibian had a retractable undercarriage. There was no indicator of its deplopyment or retractation, relying on the pilot’s memory and training. As a true marine bird, it had folding wings so they needed to be relatively forward on the fuselage and find a partiular balance.

The fuselage received an oval cross-section with planing bottom, two steps, boat shaped with a inverted slope forward as deflector. The fuselage was divided into several watertight compartments, mixing a wooden skin, and metal from the frame. The three-man crew comprised the pilot forward of the wings and propeller behind and above his head, the observer and radio having access to an open cockpit below and aft of the wing. The observer was also MG-gunner, with a flexible mounted Lewis LMG.

The pilot was seated in “safe” distance from the propeller but also far from the other crew members, separated by the fuel tanks. Communication was difficult. There was a single retractable machine gun aft for the observer to manage. In case of jamming it was easy to access and service. The radio operator sat behind the wing followed by the rear gunner position and had the least enviable position.

Engine

The Napier Lion IIB W-12 water-cooled piston engine, 492 hp (367 kW) could power the Seagull to 98 mph (158 km/h, 85 kn) at 3,000 ft (914 m) or 92 mph (80 kn; 148 km/h) at 6,500 ft (1,981 m). Endurance was the same as the Seal, four hours and 30 minutes at cruise speed. Service ceiling was 9,150 ft (2,790 m) and time to altitude was 3,000 ft (914 m) reached in 7 minutes 43 seconds, which was not stellar. In 1936, the Seagull was not going to escape any fighter by a long shot.

37 ft 9 in (11.51 m)

Service

Seagull III

Two Seagulls entered the 1924 King’s Cup Race with the Air Ministry’s authorisation. In 1925, the Seagull Mk II tested a first catapult launch and went on testing various designs of catapult either using cordite charges or compressed air before introduction. The same year, the Admiralty advised the Royal Australian Air Force (RAA) to acquire the new seaplane carrier and replace the obsolete Fairey IIIDs planned for the new HMAS Albatross. The first RAN Seagulle arrived unassembled in April 1926 at the RAAF Base of Point Cook near Melbourne, operated by the No. 101 Flight RAAF formed in June 1926.

Later they were moved to the RAAF Base Richmond in August 1926 and worked with HMAS Moresby, in 1926-1927. They were used to make a photographic survey of the Great Barrier Reef. HMAS Albatross spared the need for land facilities. Prior to their delivery, the RAN already used seaplanes for extensive photographic survey flights and covered areas from the Great Barrier Reef to the Persian Gulf. After January 1927, three more Seagulls were purchased and these surveys were extended to New Guinea.

From February 1929 to April 1933, six Seagulls served on board HMAS Albatross, for spotting, shadowing vessels (specially those of the IJN) and reconnaissance for the fleet. They were transferred to HMAS Canberra and HMAS Australia when she entered reserve in 1932, but it was soon realized the Seagull could not stand the catapult launch and started suffering from structural failures.

Seagull IIIs were withdrawn from service or scrapped in 1936 and the Albatross was purchased by the RN two years later after an arrangement wirth the RN but served as a repair ship afterwards. The Seagull III was replaced by the far better Seagull V (Walrus). A9-6 and A9-8 were moved to technological institutes for various tests, however the use of these in civilian service is not well attested. Granted, the wood of their fuselage started to experience sagging and degradation after ten years so it was probably brief.

Gallery

Author’s illustrations: Types and liveries

Seagull III in RAN service

Additional photos

Seagull III at Richmond Austrlia, 1928 (AWM)

Seagull at the King’s cup race.

Seagulls at Bowen in Queensland

Seagull II registerd N146

Seagull III A9-9 taking off

Seagull III A9-8 at sea, met by a launch.

Seagull III in 1930 AWM.

Seagull III on HMS Albatross, just lifted off from the elevator.

Links and resources

Air Force History Branch (2021). Aircraft of The Royal Australian Air Force. New York: Big Sky Publishing.
Andrews, C. F. & Morgan, Eric B. (1981). Supermarine Aircraft since 1914. London: Putnam.
Brown, David (1971). Cain, Charles W. (ed.). Profile 224: Supermarine Walrus & Seagull Variants (PDF). Vol. 11. Windsor, UK: Profile Publications.
Shelton, John K. (2015). From Nighthawk to Spitfire: The Aircraft of R.J. Mitchell. History Press.
Thetford, Owen (1994). British Naval Aircraft Since 1912. London: Putnam.
Duval, Godfrey Richard (1966). British Flying-Boats and Amphibians 1909-1952. Fallbrook, California: Aero.
Shelton, John (2008). Schneider Trophy to Spitfire: The Design Career of R.J. Mitchell. Sparkford: Hayes Publishing.

Seal II
Seagull III A9-6
Supermarine Seagull at Southampton, in trials.
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seapower.navy.gov.au
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More CC photos
awm.gov.au coll. seagull
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The model corner

Scalemates: Seagull II in British and Japanese service, Seagull III RAN, etc.
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