Martin-Baker Aircraft actually began the MB 5 as the second Martin-Baker MB 3 prototype, designed to Air Ministry Specification F.18/39 for an agile, sturdy Royal Air Force fighter, able to fly faster than 400 mph. After the first MB 3 crashed in 1942, killing Val Baker, the second prototype was delayed. A modified MB 3 with a Rolls-Royce Griffon was planned as the MB 4, but a full redesign was chosen instead.
The re-designed aircraft, designated MB 5, used wings similar to the MB 3, but had an entirely new steel-tube fuselage. Power came from a Rolls-Royce Griffon 83 liquid-cooled V-12 engine, producing 2,340 hp (1,745 kW) and driving two three-bladed contra-rotating propellers. Armament was four 20 mm Hispano cannon, mounted in the wings outboard of the widely spaced retractable undercarriage.
It was built under the same contract that covered the building of the MB.3.
The first flight of the MB 5 prototype, serial R2496, took place on 23 May 1944. Performance was considered outstanding by test pilots, and the cockpit layout was praised by the Armament and Aircraft Experimental Establishment. The accessibility of the fuselage for maintenance was excellent, thanks to a system of detachable panels.
"In my opinion this is an outstanding aircraft, particularly when regarded in the light of the fact that it made its maiden flight as early as 23rd May 1944"
– Test pilot Capt. Eric Brown, 1948
Acknowledged as one of the best aerobatic pilots in the UK, S/L Janusz Żurakowski from the Aeroplane and Armament Experimental Establishment (A&AEE) at RAF Boscombe Down gave a spectacular display at the Farnborough Air Show in June 1946, with the Martin-Baker MB 5, a design he considered as a superlative piston-engined fighter, better in many ways than the Spitfire.
Serial production, had it been authorised, would have begun in time for squadron service over Germany. Instead, the RAF directed their attention towards jet-powered fighters and the MB 5 remained unordered. Perhaps one of the reasons that the MB 5 did not go into production, was because the Rolls Royce Griffon engine failed when the MB 5 was being demonstrated to Prime Minister, Sir Winston Churchill, the Chief of the Air Staff and a host of other VIPs at an important display of British and captured German aircraft at Farnborough. Another reason, stated by Michael Bowyer, is that Martin-Baker may have lacked both facilities and sufficient government support. The company's slow progress with the machine could have been due to a lack of facilities.
A partial replica is being built in Reno, Nevada, USA by John Marlin using wings from a P-51 Mustang. The website stated in 2006 that it was nearing completion, and as of 2010, an undated entry shows a photograph of the aircraft taxiing and says that it is nearing completion.
Length: 11.5 m
Wingspan: 10.7 m
Height: 4.5 m
Wing area: 24.3 m²
Empty weight: 4,188 kg
Loaded weight: 5,216 kg
Max. takeoff weight: 5,484 kg
Powerplant: Rolls-Royce Griffon 83 liquid-cooled V-12 engine, 2,340 hp (1,745 kW)
Maximum speed: 740 km/h at 6,100 m
Range: 1,770 km
Service ceiling: 12,190 m
Rate of climb:19.3 m/s
Armament: 4× 20 mm Hispano Mk.II cannon