Metropolitan-Vickers F.2

The Metropolitan-Vickers F.2 is an early turbojet engine and the first British design to be based on an axial-flow compressor. It was an extremely advanced design for the era, Whittle was distraught but was convinced that he should patent the idea anyway. Five years later a group of investors persuaded him to start work on what would be the first working British jet engine.

Griffith continued development of his own concepts, eventually developing an advanced compressor design using two contra-rotating stages that improved efficiency. His partner, Hayne Constant, started discussions in 1937 with Manchester-based Metrovick, a maker of steam turbines, to produce the new machinery. By 1939 this work had developed several improved versions of the Betty compressor design, which were incorporated into the new Freda. Incidentally, Metrovick had recently merged with British Thomson-Houston, another turbine builder who were supporting Whittle's efforts.

In April 1939, Whittle gave a startling demonstration of his experimental engine, the WU, running it for 20 minutes at high power. This led to a rash of contracts to build a production quality design suitable for aircraft use. Metrovick's head of design, David Smith, decided to end development of the turboprop concepts and focus on pure-jets instead. Development had just started when Whittle started building his W.1 design, planning to install one for flight in the Gloster E.28/39 the next year.

F.1

In July 1940 the RAE signed a contract with Metrovick to build a flight-quality pure-turbojet engine based on the Freda turbine. This emerged as the F.1 concept, which was built in several forms, with the first running engine starting on the testbed in late 1941. The design cleared its special-category flight-tests in 1942, and flew for the first time on 29 June 1943 in the open bomb bay of an Avro Lancaster. Compared to the centrifugal-flow Whittle designs, the F.1 was extremely advanced, using a nine-stage axial compressor, annular combustion chamber, and a two-stage turbine. Production quality versions of the F.2 were tested on the F.9/40M (Gloster Meteor) s/n DG204/G, which made its first flight on 13 November 1943. They were installed in underslung nacelles, in a manner similar to the engines of the Messerschmitt Me 262.

The axial compressor of the F.2 was later offered to Rolls-Royce and used as the initial stage of the Rolls-Royce Clyde.

F.2/2

To address these problems, in August 1942 a minor redesign delivered the F.2/2, which changed the turbine material from Rex 75 to Nimonic 75, and lengthened the combustion chamber by . Thrust was improved to static, but the problems with overheating remained.

F.2/3

Another attempt to solve the overheating problems resulted in the more highly modified F.2/3 during 1943. This version replaced the original annular combustion chamber with can-type burners like those on the Whittle designs. This appears to have solved the problems, raising the thrust to in the process. However, by this time it was decided to move on to a much more powerful version of the engine.

F.2/4 Beryl

Development of the F.2 continued on a version using a ten-stage compressor for additional airflow driven by a single stage turbine. Apart from the first stage nozzle guide vanes, the LP turbine was completely statorless, with four consecutive rotor stages. Rotors one and three drove the front fan clockwise (viewed from the front), whereas the rear fan was driven anticlockwise by rotors two and four. Although the front fan had inlet guide vanes, there were no vanes between the contra-rotating fan rotors or, downstream, any exit guide vanes. The core and bypass streams exhausted through separate coaxial propelling nozzles.

The project was generally successful, raising static thrust from around ( in 1947). Furthermore, specific fuel consumption fell from , which was the true aim of the project. The weight increase for all the extra turbomachinery and ducting was significant, however. A bonus was a marked decrease in noise levels which resulted from the slower, cold air from the fan mixing with the fast, hot exhaust from the gas generator.

Although the F.3 progressed nicely, development was curtailed by the pressures of war. When the war ended the F.2/2 was no longer current, so some of the ideas were applied to the more up-to-date F.2/4 to produce the Metropolitan-Vickers F.5 propfan.

F.5

Following on where the F.3 left off, the F.5 was a version of the F.2/4 with an open rotor (unducted) thrust augmenter added to the end of the jet pipe, somewhat remote from the HP turbine The 5 ft 6 in diameter fixed pitch propellers, which contra-rotated, were driven by a four-stage statorless LP turbine unit, similar to that of the F.3. Static thrust increased from the 3,500lbf of the F.2/2 to in excess of , with a corresponding reduction in specific fuel consumption. Relative to the parent turbojet, the weight increase for this prop fan configuration was about 26%, compared to 53% for the F.3 turbofan. Development was cancelled when they sold their gas turbine business to Armstrong Siddeley in 1946.

F.9 Sapphire

Development of the F.2 ended in 1944. Development of the basic concept continued, however, eventually leading to the considerably larger F.9 Sapphire. However, in 1947, Metrovick left jet engine production and their design team moved to Armstrong Siddeley. The Sapphire matured into a successful design, initially besting the thrust of its Rolls-Royce contemporary, the Avon. Design features of the Metrovick line were worked into Armstrong Siddeley's own line of axial compressor turboprops, although Armstrong Siddeley dropped Metrovick's use of gemstone names for their engines in favour of continuing with animal names, in particular snakes.

An example of the prototype engine can be found in the Science Museum Flight Gallery in London.

Engines on display

A Metrovick Beryl is on display at the Rolls-Royce Heritage Trust (Derby).

Specifications (F.2/2)

thumb|On display at the Rolls-Royce Heritage Trust (Derby)

References

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External links

"Metro-Vick Gas Turbine" a 1946 Flight article
"Metrovick F.5" a 1947 Flight article on the F.5 propfan

F.1