This aircraft is believed to be the only surviving World War II prototype to be preserved anywhere. It was the first of an initial order for 50 bomber/reconnaissance Mosquito’s to Specification. B.1/40 ordered on I March 1940 to contract No. 69990. It was moved to Hatfield by road on 3 November 1940 painted overall yellow for easy identification, and made its first flight as E0234 on 25 November. It created such a good impression with Lord Beaverbrook and other senior Government Ministers at a demonstration at Langley on 29 December that the go-ahead for a further 150 aircraft was given the next day.
Re-numbered W4050, the prototype reached an altitude of 22.000 ft on 17 January 1941, and was delivered to Boscombe Down on 19 February with camouflaged upper surfaces for initial service trials. Due to the rough surface of the airfield the tail wheel jammed while taxiing in on 24 February and the fuselage fractured around the starboard side access hatch. The damage was serious enough for the decision to be made to change the fuselage, the fuselage of the PR. I prototype W4051 being taken from Salisbury Hall to Boscombe Down to be changed by a & Havilland working party. W4050 returned to Hatfield on 14 March, for further adjustments, returning to Boscombe Down four days later for handling trials, with the extended engine nacelles, until 23 March. On 4 May the prototype made its 100th flight, returning to Boscombe Down, the maximum level speed achieved being 392 mph at 22,000 ft an all-up weight of 16,000 lb. During further handling tests at Boscombe Down the fuselage was again damaged during a heavy landing, cracking on the port side, resulting in the irregular patch, still visible, just behind the wing trailing edge. Service tests were completed on the prototype at Boscombe on 23 May, to be continued on later aircraft.
The prototype was used by de Havilland for stall tests in a number of configurations, and in late October it was grounded for the fining of the more powerful supercharged Merlin 61 engines, flying again on 20 June 1942 attaining an altitude of 40,000 ft on its second flight. Merlin 77s were then fitted, with flight trials recommencing on 8 October, allowing a top speed of 439 mph to be reached in November, the highest speed by any Mosquito in level flight. Test flying continued at a lower rate in 1943, including a short spell with Rolls-Royce from 1st March to 10th June. The following year W4050 was grounded, to be used for apprentice training. it was shown publicly in the static park at the SBAC displays at Radlett in September 1946 and 1947 surrounded by a selection of its weapon loads, and was declared Cat.E and struck off charge on 21 June 1947. being stored on various locations at Hatfield, Chester and Panshangar. It was moved back to Salisbury Hall in early 1959. and put on public display, for the first time, on 1st May of that year.
Photo and text: de Havilland Heritage Centre
