The Supermarine Sea Lion was a racing version of the Sea King scout plane. Three versions were produced and were entered in the Schneider Trophy Races of 1919, 1922 and 1923, winning in 1922.
The Sea King/ Sea Lion was a biplane flying boat, powered by a pusher engine mounted between the wings. The pilot sat in an open cockpit just in front of the wings.
The first racing version was the Supermarine Sea Lion I, G-EALP, a single-bay flying power with un-staggered wings and a pusher 450hp Napier Lion IA engine between the wings. This aircraft was probably a modified version of the Sea King I, although that isn't entirely certain. This was one of several British entries for the 1919 contest, which was held at Bournemouth. Unfortunately the weather turned against the competitors. Heavy fog forced all of the aircraft to land, and when the Sea lion attempted to take off later it was damaged in a collision with a floating object. The Sea Lion I survived this collision, but when it landed again sank. The aircraft was later raised, but didn't fly again. Eventually the contest was cancelled without a winner, although the Italians were asked to hold the next contest, as they had reached the highest speed before the fog stopped play.
The Sea Lion II was originally constructed as a amphibian scout aircraft, the Supermarine Sea King II. This made its maiden flight early in 1922, but despite a good performance didn’t sell. It was chose to be the basis of the British entry for the 1922 Schneider Trophy, a privately funded team led by Hubert Scott-Pine and Commander James Bird (one of the directors of Supermarine). The aircraft was redesigned by R.J. Mitchell. It was given smaller equal-span wings and became a single-span pusher flying boat. The amphibious landing gear was removed. The aircraft was powered by a 450hp Napier Lion engine, which was loaned to the team by Napier. In its new configuration it was renamed as the Sea Lion II.
The race was held on 10-12 August, and the Sea Lion II was flown by Captain Henri C. Biard. The only competition came from the Italians, who entered the Macchi M.7, Macchi M.7 Naval and S.I.A.I Savoia S.19, all pusher biplanes.
The Sea Lion II flew the 230 miles triangular course in 1hr 36min 22sec at an average speed of 145.7mph, giving Britain her second victory in the trophy. This performance was also awarded a series of world records – for duration, longest distance and fastest times to cover 100km and 200km, although as this was the first time these records had been set this isn't quite as impressive as it seems!
The aircraft was redesigned again for the 1923 Schneider Trophy. This time Mitchell gave it two-bay wings, a longer fuselage, wingtip floats and a 525hp Lion engine. In this configuration it became the Sea Lion III.
Britain also entered the Blackburn Pellet, but this aircraft suffered from two accidents before the race, sinking after the second one. The main competition came from the first military entry into the contest – two US Navy Curtiss C.R.3 floatplanes. These were dramatically different to the flying boats that had won in previous years, and won an overwhelming victory. The contest was won by Lt David Rittenhouse, USN, at an average speed of 177.38mph. Biard, in the Sea Lion III, could only manage third, at 151.16mph.
The Sea Lion III was lost in an accident in July 1924, when a pilot who was unfamiliar with it stalled at take off and was killed.
This defeat forced Mitchell to reconsider the design of his racing aircraft, and his next Schneider racer would be the Supermarine S.4, the first in a series of racing aircraft that gave Mitchell valuable experience of designing advanced monoplane aircraft, and thus played a part in the design of the Supermarine Spitfire.
Sea Lion I
Engine: Napier Lion IA
Length: 26ft 4in
Height: 12ft 3in
Empty weight: 2,000lb
All up weight: 2,900lb
Max speed: 147mph
Endurance: 2hr 30min
Sea Lion II
Engine: Napier Lion II
Length: 24ft 9in
Height: 12ft 0in
Empty weight: 2,115lb
Loaded weight: 2,850lb
Max speed: 160mph
Endurance: 3 hours
Sea Lion III
Engine: Napier Lion III
Empty weight: 2,400lb
Maximum take-off weight: 3,275lb
Max speed: 175mph
Endurance: 3 hours