Robert Blackburn announced in March 1923 that his company, the Blackburn Aeroplane and Motor Co Ltd of Leeds, was to build an entry for the 1923 Schneider Trophy Contest, and the event was set for 28 September, with Cowes, on the Isle of Wight, as the starting and finishing point. The aircraft was to be a single-seat flying boat and the company had only worked on one flying boat before, the NAB single-seat fleet escort bomber of 1918 and that had never been completed.
Blackburn's chief test pilot, Reginald W. Kenthworthy, wanted the aircraft to be ready for test flying in August, a month before the race, so that any problems could be resolved and he could gain some handling experience on an untried prototype.
The design of the aircraft was largely determined by the use of the hull of the NAB, a streamlined structure which comprised circular wooden formers separated by stringers and planked with diagonal mahogany strips in two layers crossing each other at right angles. To this hull was added, a biplane wing structure, comprising singlebay sesquiplane wings, the lower wing being of less span and chord than the upper and having no ailerons. The wing structure was attached to the top of the hull and on the top centre section, supported by N struts, was mounted a 450 hp Napier Lion, in a close fitting, streamlined nacelle. It was the engine from the Gloster Bantel, which had won that year's Aerial Derby. Wooden wingtip floats were fitted beneath the outboard N struts of the narrow-gap wings. The open cockpit had a well r raked windscreen and there was a streamlined fairing behind the he pilot's head. A strut-braced tailplane was Positioned half-way up to the fin.
The flying boat was eventually named the Pellet and the civil registration G-EBHF was allotted to it on 23 July.
Despite efforts to complete the Pellet on time, its engine was not available until August and it was not finished until the first week of September. After some engine runs it was launched down the Brough shipway with Kenworthy in the cockpit. Unfortunately, it was caught by the Humber tide and the crosswind, dipped its starboard wingtip float and turned turtle and sank, ejecting Kenworthy into the river.
It was only three weeks before the contest, but Robert Blackburn was undeterred. The Pellet was stripped, repaired and given larger wingtip floats and the engine was returned to Napiers for cleaning. Five days before the event, the Pellet was again ready, but, as there was no time to fly it at Brough, it was sent by rail to Fairey's yard at Hamble, Southampton, for assembly and testing.
On 26 September, only two days before the contest and the day before the preliminary tests, the Pellet was relaunched, now displaying the racing number 6 on its fuselage and rudder. During the take-off run it shipped a lot of water, but took off successfully. Kenworthy then found that he needed all of his strength on the control column to prevent the Pellet diving, as it was extremely nose-heavy. To complicate matters, the wing-mounted recessed radiators proved inadequate and the cooling water boiled. With no choice but to alight, Kenworthy put the troublesome machine down on the sea just past the RAF seaplane base at Calshot and was eventually retrieved by a motor boat from S.E. Saunders Lid, which towed it to Cowes.
Working through the night, Saunders' staff fitted a large Lamblin 'crab-pot' radiator beneath the engine nacelle and bypassed the wing radiators. The original two-bladed wooden aircrew had been damaged by spray so a two-bladed metal unit was, installed. The fin chines were reinforced and adjustments were also made in an attempt to settle the problem with the centre of gravity.
By 11.48 next morning, just before the final launching time for the navigability and watertightness tests, the Pellet was ready, However, as Kenworthy began his takeoff run down the River Medina, a heavy swell turned the machine slightly to the right so that it was heading straight for two rowing boats. Kenworthy tried to change direction: 'the machine, travelling at about 140 mph jumped and jumped', Kenworthy told a Daily Graphic reporter. It then left the water in a stalled attitude, coming down twice with great force before it tipped over to starboard. The wingtip float touched the water and the Pellet made a final leap before diving nose down and turning right over.
Kenworthy was picked up unharmed by Lord Montagu of Beaulieu in his motor boat, fainted and was revived by artificial respiration. He had been under the hull for 61 seconds. The Saunders works manager, Mr Newman, recovered the Pellet that night, but this time it was beyond repair. Robert Blackburn never built another Schneider Trophy racer.
Engine: One 450 hp Napier Lion W-12
Upper span: 34 ft
Lower span: 29 ft 6 in
Length: 28 ft 7 in
Height: 10 ft 8 in
Maximum speed (estimated): 122 mph