Martin Baker MB 5 – The Ultimate Fighter That Never Was

The Martin-Baker MB 5 was developed as an advanced, extremely fast fighter aircraft to help the British war effort in 1943. It was designed as part of a series of experimental prototype aircraft by Martin Baker to meet a specification from the British Air Ministry to build a fighter that could operate in tropical conditions.

The Martin Baker company responded to the specification as a private venture and developed a series of aircraft that would eventually evolve into the MB 5.

Although one of the company’s founders and namesakes, Valentine Baker, was killed when testing one of the earlier prototypes, this spurred the company’s remaining founder James Martin to pour a great amount of effort and attention to detail into the MB 5.

The finished result was an aircraft that defied expectations and was praised by test pilots. Despite the innovative design and the highly positive reception, the MB 5 was not selected for production, in part due to Martin’s attention to detail delaying the MB 5’s release and the incoming jet age rendering piston propeller planes obsolete in the eyes of military strategists.



The origins of the MB 5 came as part of a group of experimental aircraft designed by the Martin-Baker company in the United Kingdom. Although Martin Baker would become renowned for making aviation safety equipment, most notably ejector seats, the company had sought to develop their own aircraft in the 1930s.

Their experimental designs included an autogyro for Austrian-born inventor Raoul Hafner and a fixed-wing plane with a de Havilland Gipsy engine mounted at the rear.

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Towards the end of the 1930s, Martin Baker moved towards more conventional aircraft designs with the MB 1 prototype, a fixed-wing light aircraft.

On the eve of the Second World War, the British Air Ministry issued a specification for a fighter plane that could cope with tropical conditions. The company’s two founders, Valentine Baker and James Martin, set to work on designing potential aircraft that could meet the specification.

Martin Baker began their attempts at military aircraft with the MB 2 concept. It was designed as a private venture without funding from the government or Royal Air Force.

The concept used an existing Napier Dagger power plant but attempted to incorporate design features that were unique at the time including a fuselage that was longer than the wings. Despite this, RAF proving trials deemed the MB 2 to have design limitations and was not selected for production.

Both Martin and Baker were undeterred by this and continued to work on new designs. Their next attempt was the MB 3. The MB 3 was created in response to another British Air Ministry specification for an extremely fast, agile fighter that could be a potential successor to the Hurricane and the Spitfire.

The MB 3 prototype in the early 40s. This looked very similar to a Spitfire.
The MB 3 prototype in the early 40s. This looked very similar to a Spitfire.

This drew upon the MB 1 and 2, incorporating some of their design features but adding a more powerful 2,000 horsepower Napier Sabre engine unit and armament consisting of six Hispano cannons mounted in the nose and wings

One prototype example was built in 1942 and initial tests showed promise, with the MB 3 reaching a speed of up to 420 miles per hour during its maiden flight. However, the project was tragically cut short when Valentine Baker was killed while taking the MB 3 for a test flight.

An investigation determined that Baker had hit a tree stump while trying to perform an emergency landing.

The crash prompted Martin to reorientate the company’s focus on producing safety equipment to save the lives of pilots but his ambition to make a success of the MB series was not dampened.

He initially continued with the MB 4 which was essentially a redesign of the MB 3 but intended to carry the Rolls Royce Griffon engine which Martin was able to obtain after negotiations. This design did not end up leaving the drawing board. Although the future of the MB series looked in doubt, Martin persevered.

Rolls-Royce Griffon V12
The Rolls-Royce Griffon had a significantly larger displacement than Merlin (37 litres versus 27 litres), but produced more power.

As luck would have it, the Air Ministry specification was still open and Martin continued to redesign the aircraft.

MB 5

Martin decided to design a new airframe from scratch and took a perfectionist approach, wanting to avoid any accidents which had led to the death of his colleague.

Although a more intricate design would take longer to complete, Martin paid close attention to detail in all aspects of the plane. He decided the MB 5 would use similar wings to the MB 3 but with a modified, steel tube fuselage.

The power would still be provided by a Rolls Royce Griffon V12 liquid-cooled engine unit which could produce up to 2,340 horsepower.

The MB 5 prototype taking off.
The MB 5 prototype taking off.

The engine would drive two contra (opposite) rotating propellers at the nose while the undercarriage was designed as retractable and spaced out under the wings. The wingspan itself totalled around 30 feet while the empty weight stood at 12,090 pounds.

The proposed armament consisted of four 20 mm Hispano cannons mounted in the wings.

Although Martin sought to approach the design with special care, he also wanted it to be defined by ease of maintenance and simplicity. Much of the fuselage structure was boxy and featured straight lines and simple conformation over curves or unusual shapes.


Due to Martin’s strong focus on perfecting the design, the MB 5’s production schedule fell behind its projected release date of the 1st of January, 1943.

Instead, the first prototype was unveiled the following year. It was sent for its maiden flight on the 23rd of May, 1944 under the control of pilot Bryan Greensted who worked as the chief test pilot for the propeller manufacturer Rotol.

“Jimmy” Martin in front of the MB 5
“Jimmy” Martin in front of the MB 5. Photo credit – Martin Baker.

Although things again seemed promising with the initial test, the aircraft was later taken back by Martin for more development at the Martin Baker plant and he added modifications including detachable panels around the cockpit.

The aircraft was resubmitted for proving trials in February 1946 at the RAF’s Armament Experimental Establishment at Boscombe Down. By this stage, the war had ended before the MB 5 could be put into production and active service.

Despite this, the RAF opted to continue tests on the aircraft and it was handed back to Greensted once Martin’s modifications were complete. Greensted praised the MB 5 and lauded it as a “super ship to fly” that “earns the respect of everyone associated with it.”

Even Eric Brown thought the aircraft was something special.
Even Eric Brown thought the MB 5 was something special.

The MB 5 was also flown by renowned Royal Navy test pilot Captain Eric Brown who summed it up as an “outstanding aircraft.” Further test runs were also met with positive feedback from pilots and the British Aeroplane and Armament Experimental Establishment who praised the cockpit layout.

Although a test run for Prime Minister Winston Churchill did not meet expectations, the MB 5 was able to prove itself during a further demonstration when it was handed to Polish flying ace Janusz Żurakowski who gave a public demonstration flight at the Farnborough Air Show in June 1946.

Żurakowski also praised the MB 5 and even described it as superior in some respects to the Spitfire.

The test reports summarised the MB 5 as having excellent stability, especially when firing its cannons, while also having agile and responsive manoeuvrability. These were traits considered difficult to pull off at the same time and indicated the MB 5 would have made a powerful dogfighter if it was to enter military service.

Test pilots and engineers assessed that the top speed was around 460 miles per hour when flying at 20,000 feet. It also had an initial climb rate of 3,800 feet per minute and a service ceiling of around 40,000 feet. Its range was calculated to be within the region of 1,000 miles.

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At the end of testing, the MB 5 had shown great potential and improvement on Martin Baker’s previous designs with the attention to detail, the plane’s late development as a result of perfection also worked against it.

The aftermath of the war heralded the incoming jet age for future military aircraft designs. Germany had already produced the Messerschmitt Me 262, followed by Britain with the Gloster Meteor and then America with the Lockheed P-80 Shooting Star.

The Korean War also saw dogfights between jet aircraft, although some NATO pilots complained that their jet planes were actually too fast to combat with North Korean propeller aircraft.

Unfortunately no one really knows what happened to the MB 5 prototype.
Unfortunately, no one really knows what happened to the MB 5 prototype.

An agile propeller aircraft like the MB 5 may have proved ideal for such an engagement, but Martin Baker was not offered further financial support to expand their facilities and pursue mass production.

The sole prototype had its engine removed before it was sent to RAF Wattisham, Suffolk in the late 1940s for use as a training aircraft. Some sources claim the MB5 was destroyed on a gunnery range as part of a target practice exercise. Other aviation historians have argued it was dismantled and then burnt.

Although its fate is debated, the MB 5 perhaps represented one of the greatest aviation potentials that never was.

The Martin Baker company did not heavily invest in further aircraft production after MB 5, but established itself as a famous manufacturer of ejector seats, cementing Martin’s reputation for his focus on pilot safety.

Replica Revival

Although the original MB 5 airframe was lost, a replica of the plane was built by John Marlin of Reno, Nevada.

The MB 5 replica in 2006
The MB 5 replica in 2006. Photo credit – Ericg CC BY-SA 2.5.

Marlin began work on the replica in 2001 but had to source the wings from a P-51 Mustang due to the loss of the original wings. He reportedly began putting the replica through the ground and taxing tests in 2006.

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The replica was described as being six feet shorter than the original plane and was listed as being for sale in 2017, although doubts were raised as to whether it was able to fly.

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  • Crew: 1
  • Length: 37 ft 9 in (11.51 m)
  • Wingspan: 35 ft (11 m)
  • Height: 12 ft 6 in (3.81 m) including propeller
  • Empty weight: 9,233 lb (4,188 kg)
  • Gross weight: 11,500 lb (5,216 kg)
  • Max takeoff weight: 12,090 lb (5,484 kg)
  • Powerplant: 1 × Rolls-Royce Griffon 83 V-12 liquid-cooled piston engine, 2,035 hp (1,517 kW)
  • Maximum speed: 460 mph (740 km/h, 400 kn) at 20,000 ft (6,100 m)
  • Range: 1,100 mi (1,800 km, 960 nmi)
  • Service ceiling: 40,000 ft (12,000 m)
  • Rate of climb: 3,800 ft/min (19.3 m/s)