Gloster E.28/39 (W4041/G) [@ Science Museum]
In September 1939, the Air Ministry issued a specification to Gloster for an aircraft to test one of Frank Whittle's turbojet designs in flight. Working closely with Whittle, Gloster's chief designer George Carter laid out a small low-wing aircraft of conventional configuration. The jet intake was in the nose and the tail was mounted above the exhaust. The Air Ministry signed a contract for two prototypes on 3rd February 1940 and the first of these, W4041/G, was completed by April 1941.
W4041/G was delivered to Hucclecote for ground tests beginning on 7th April, using a non-flight worthy version of the Power Jets W.1 engine. Rover was unable to deliver the W.1 production engine before Gloster's experimental airframe was ready. Whittle then cobbled together an engine built from various test parts and called it the W.1X, which ran for the first time on 14th December 1940. This engine powered the Gloster E.28/39 for taxi testing when it took to the air for a short hop on 7th April 1941. With these satisfactorily completed the aircraft was fitted with a new W.1 turbojet, giving 3.8 kN (850 lbf) of thrust, and on 15th May 1941 at 7:40pm Gloster's chief test pilot, Flt Lt Gerry Sayer, flew W4041/G under jet power for the first time from RAF Cranwell in Lincolnshire. The flight lasted seventeen minutes and was a complete success. Within days W4041/G was reaching 600 km/hr (370 mph) at 7600 meters, exceeding the performance of the contemporary Spitfires. Tests continued with increasingly refined versions of the engine over the following months.
The WU (Whittle Unit) was the first turbojet to run on the 12th April 1937. The photograph [right] shows the WU in its third and final form. Designed for test-bed running only it led to the development of the W.1. Many difficulties were uncounted during development, notably unreliable combustion. In addition, limited finance required the continual use of original parts from the first version of the engine. The WU featured a double sided centrifugal compressor, ten reverse-flow combustion chambers and a single stage turbine.
Gloster E.28/39 (W4041/G) [@ Science Museum]
The second prototype joined the test programme on 1st March 1943 and was initially powered by a Rover W.2B engine. The aircraft was destroyed on 30th July in a crash resulting from an aileron failure, however, W4041/G continued flight tests until 1944. Experience with the E.28/39 paved the way for Britain's first jet fighter aircraft, the Gloster Meteor. The E.28/39 specification had actually required the aircraft to carry two Browning .303 machine guns in each wing but these were never fitted.
The Gloster E.28/39 (also referred to as the "Gloster Whittle", "Gloster Pioneer", or "Gloster G.40") was Britain's first successful jet aircraft and first flew on 15th May 1941 at RAF Cranwell. W4041/G could carry only 82 gal of fuel, limiting the test flights to 30-40 minutes, but flights of up to 42,000 ft were made and Mach 0.82 was reached in a dive. In 1946 this first prototype, W4041/G, was placed in the Science Museum.
The engine shown above was the actual engine that powered E.28/39 on the maiden flight of 15th May 1941. The W.1 was designed by Frank Whittle and his team at Power Jets Ltd and was based upon he final form of the WU. It had a double sided centrifugal compressor, ten reverse flow interconnected combustion chambers and a single stage turbine. Thomson-Houston, a British company, constructed the engine under the direction of Whittle.
The Whittle W.2/700 "centrifugal flow" power plant and an example of a "axial flow" design (Bristol-Siddeley Viper)
The Whittle W.1 had a "centrifugal flow" configuration meaning that its compressor was based on an impeller design, rather like a pump, and not a series of fans as used in the more modern "axial flow" turbojets. Centrifugal flow engines would eventually prove to be a dead end as far as high-speed jet aircraft were concerned, though turboprop and turboshaft engines still use the configuration. However, at the outset of the jet age, the centrifugal flow engine was perfectly effective and in fact much easier to get into service than the axial flow engine.
The Whittle W.2 reverse flow combustion system incorporated into the design of the Gloster E.28/39
The company formed by Whittle, Power Jets Ltd at Lutterworth in Leicestershire, designed and produced the W.1 engine. The W.2 [photographs - above] was the second generation Whittle engine and typical of Whittle designs it had the “reverse flow” combustion system in which the hot air was piped back to the middle of the engine in order to "fold" it and reduce its length. It was eventually developed to give nearly three times the thrust of the W.1 without occupying more space. In May 1940 Power Jets designed the W.2Y engine. Of similar design to the W.2 but with a straight through” airflow it resulted in a longer engine and driveshaft but with a somewhat simpler layout. In 1941 Rover set up a new laboratory for Whittle's team along with a production line at their disused Barnoldswick factory to produce the W.2B to Whittles original W.2 “reverse flow” design. The first flight-test of the engine itself took place on 9th August 1942 attached to a Vickers Wellington. An eventual total of 167 engines started rolling off the production line in October 1943, first known as the W.2B/23 [photograph - below, right], then the RB.23 (for Rolls Barnoldswick), and eventually in 1943 as the Rolls Royce Welland. The W.2/500 [photograph - below, middle] and the W.2/700 [photograph - below, right] were the final developments of the W.2 engine.
Meanwhile Rover had set up a parallel team with their own engineers, led by Adrian Lombard, at Waterloo Mill, Clitheroe to produce a production quality design of the W.2Y to be known as the W.2B/26. Whittle was annoyed by this course of events feeling in the interests of the war effort that all work should concentrate on developing the proven W.2 “reverse flow” variant. The W.2B/26 prototype ran in March 1942 and served as a direct basis for the Rolls Royce Derwent I [photographs - below] engine (1943).
The Barnoldswick factory was too small for full-scale production so a new factory was set up in Newcastle-under-Lyme with the W.2B/26 or Derwent I opening the new production line. By this time the Derwent’s straight-through design had proven itself to be both more reliable and somewhat more powerful than the Welland’s design. This allowed the production lines at Barnoldswick to shut down in late 1944 and the facility turned back into a pure research.
In January 1941 de Havilland, with the aid of Frank Halford, commenced work on the H.1 or "Goblin" engine. The Goblin first ran on 13th April 1942, and within two months it was running at full design thrust. It first flew on 5th March 1943 in DG206/G, the first Gloster Meteor to fly, and on 20th September in the de Havilland Vampire. Compared to the Whittle designs, the Goblin engine used a single-sided compressor with the inlet at the front and a "straight through" layout with the flame cans exhausting straight onto the turbine. This made the H series engines somewhat simpler than Whittle's designs, notably allowing one of the main bearings to be removed. Nevertheless it was a fairly compact design even without the Whittle-style "folding". In July 1943 a Goblin was sent to the United States where it was selected to become the primary engine of the F.80. This engine was fitted to the prototype and first flew on 8th January 1944. The engine was later accidentally destroyed in testing and replaced by the Goblin from the prototype Vampire. Allis-Chalmers was selected to produce the engine in the US as the J.36 but it ran into lengthy delays. Instead General Electric was forced to give the I.40, their greatly improved 4,000 lbf version of the Rolls Royce Derwent to Allison Engines to become the Allison J.33.
The Goblin was followed by the H.2 or "Ghost" engine, four of which powered the de Havilland Comet 1 series whose first prototype flew on 27th July 1949 and the de Havilland Venom which flew for the first time on 2nd September 1949. About the same size and weight as the Goblin, the Ghost was about half again as powerful. The photographs below shows a Ghost with an attached burner unit. It was developed and built under licence for the Royal Swedish Air Force by Svenska Fygmotor A.B. as the RM 2B. The engine powered the SAAB J29 Tunnan which was Sweden’s and Europe’s first post WW2 swept wing fighter to enter service (the Messerschmitt Me 262 being the first swept wing fighter) and flew for the first time in 1951.
The first British engine to use an axial-flow compressor was the RAE/Metrovick F.2, [photograph - left] which ran on its test bed in November 1941 and was first flown on an Avro Lancaster test-bed on 29th June 1943. It was the work of A.A. Griffith and Hayne Constant, both of the Royal Aircraft Establishment. On 13th November 1943 production quality versions were installed on a Gloster Meteor F.9. As expected, the engines were more powerful than the Whittle design, first delivering 1,800 lbf (8 kN) but soon scaling up to well over 2,000 lbf. Although offering excellent performance, it was considered too unreliable for use during the war and never entered production. Although Metrovick stopped the development of the F.2 in 1944, Armstrong Siddeley continued its development into the F.9 Sapphire. The Sapphire became a successful design, bettering its Rolls Royce counterpart - the Avon, and was used as the power-plant in the Handley Page Victor. Meanwhile the Germans concentrated on the Junkers Jumo 004B [photograph - below] axial-flow turbojet engine for the aerodynamically advanced Messerschmitt ME262V-3 which made its first flight on 18th July 1942 and became operational in October 1944. The Jumo 004B was closer to the style of modern jet engines, but its reliability was not as good as the Welland due largely to England's better metallurgy and Rolls Royce's considerable experience in the related field of superchargers; it was also heavier and used more fuel than the Whittle engine.
Development work commenced in May 1944 to modify a Derwent 2 with an extra turbine stage driving a reduction gearbox and a Rotol 7 ft 11in five-bladed propeller to form the first production turboprop engine, the Rolls Royce Trent (RB.50). Most of the turboprop’s engine power is used to drive the propeller and the propellers used are very similar to the propellers used in piston engines (with the exception that turboprops usually use a constant velocity propeller). Two Trent engines were fitted to the Gloster Meteor EE227, the sole "Trent-Meteor", which became the first turboprop powered aircraft to fly on the 20th September 1945. Rolls Royce continued the development of the Derwent and extended their range of centrifugal-flow type engines, including the Nene (1944) [photographs - below]
and the Dart (1947) [photographs - below]. The Dart became one of the most reliable turboprop engines ever built, with production continuing for more than fifty years.
Similar to other manufacturers Rolls Royce switched in the 1950s to the axial compressor with their Avon range. Developed for the Canberra bomber, the Avon went on to become one of the most successful post WW2 engine designs. Rolls Royce began designing the axial-flow Avon in 1945, however, the early versions had major design problems which proved extremely difficult to overcome. After a major re-design in 1950, a new and very different Avon emerged which led to the 200 series [photograph below left, Avon 203 and photograph below right, Avon 525]. When production finally ended in 1974, 10,433 had been built for aircraft propulsion. The Avon was used in a wide variety of aircraft variants, both military and civilian e.g. the Hawker Hunter, the Supermarine Swift, the Comet, the Vickers Valiant, English Electric Lightning, de Havilland Sea Vixen . . . as well as the record breaking Fairey FD.2. The Avon was also by the Industrial and Marine Divisions of Rolls Royce e.g. for generating electricity and gas and oil pumping. In fact more have sold for these uses than any other gas turbine.
Designed from 1948 to power the Handley Page Victor bomber, the Rolls Royce Conway [photographs - below] was also used to power some Boeing 707s, DC8s and all VC10 and Super VC10 airliners. In May 1960 the Conway became the world's first bypass jet engine to enter service. In a bypass engine not all of the air taken in is fully compressed, some is compressed to produce thrust like a propeller. This is more efficient, saves fuel and reduces noise.
Today jet engines mainly use axial compressors for both military and civil applications (e.g. the Rolls Royce RB.211 [photograph - above right] which is the power-plant for many Boeing 747s and Airbus variants though the centrifugal compressor does find widespread application for small engines, most significantly for helicopters.