UK Jet Development 1943
Aircraft
Gloster G.40 E.28/37 Pioneer
Developed as a flying testbed for the Whittle W.1 gas turbine.
Dimensions; 29/ 25.3/ 9.3/ 146.5 sq ft; 1x 860lb thrust Power Jets W.1; max speed 390-410mph; service ceiling 32,000ft and loaded weight 3,750lb.
The first prototype W4041 was first flown 15 May 1941 with an 860lb W.1 engine. It was refitted with a 1,160lb W.1A in Feb 1942.
The second E.28/37, W4046, was fitted with a 1,200lb W.2 engine, and made its maiden flight in February 1943. It was then refitted with a 1,526lb thrust trial RB.23 Welland in May 1943. Unfortunately, this aircraft had a short life as it crashed and was destroyed due to aileron jamming on 30 July 1943.
The third prototype, W4047, was fitted with a 1,600lb RB.23 Welland, and was first flown on 20 September 1943. To replace the lost second prototype, W4047 was refitted with a 1,700lb rated engine during December 1943.
Gloster G.41
George Carter’s original study was approved in November 1940 and on 7th February 1941 eight prototypes were ordered (DG202-210). At the final design conference an order was made for 150 production aircraft plus the 8 prototypes. Given the likely delays with the chosen Power Jets W.2 turbojet it was also planned to use the 2,500lb Halford H.2, with this engine the max sea level speed was estimated at 470mph and with its full planned thrust near 3,000lbs speeds over 500mph were envisioned. Rampage was assigned as a security codename, Millet would be the security code for the actual test flights.
Much progress was made during 1943 as the prototypes began to be completed. DG206 made the first flight on 5 March 1943 powered by two de Havilland H-1 Goblin engines. DG202 and DG205 flew with RB.23 Welland (as the Power Jets W.2 had become) test engines on 12 June and 24 July respectively. DG203 first flew on 13 September powered by two 2,100lb Armstrong Siddeley ASX axial-flow turbojets, followed by DG204 in November with 2,000lb RB.26 Derwent turbojets. Thus the G.41 was in effect testing all the current generation of turbojets and undertaking much needed engine development work. By the end of 1943 the Gloster line was tooling up for the first batch of twenty production machines, now names Meteor, although not all of the prototypes had flown by then.
De Havilland DH.100
As Frank Halford’s H-1 engine began to mature on the test bench an aircraft was planned by de Havilland to test it and also form the basis of a fighter. The first design was the DH.99, an all-metal twin-boom fighter armed with six 20mm cannon and with a maximum weight of 8,470lbs. estimated performance was 445mph at sea level, 4,590ft/min rate of climb at sea level and an operational ceiling of 45,400ft. The Air Ministry gave the go-ahead in July 1941. The design was refined as the DH.100 with a mixed wooden-metal airframe. Two prototypes were ordered under Spec E.6/41, LZ548 and LZ551.
The first prototype made its maiden flight at Hatfield on 20 September 1943 followed by LZ551 two months later. A major problem, though eventually overcome, discovered during flight tests was snaking during high-speed runs which was cured by altering the fin shape and tail arrangement. In 1943 a hundred production fighters were ordered as the Vampire. The first production Vampire should fly in mid-1944.
New Specifications
N.11/43: Issued during 1943 to Gloster for development of navalised G.41 powered by two Rolls-Royce 750shp + 1,250lbs thrust RB.50 propeller-turbines as a carrier-based fighter-bomber.
The Admiralty having investigated the turbojet was eager not to be left behind the RAF. Analysis suggested that turbojets would be difficult to operate from carriers and that their poor fuel economy would limit their range. Rolls-Royce was working on a more economical propeller-turbine and it was felt that this powerplant might be more suitable. Arrangements with the Air Ministry saw one of the early production G.41 airframes being earmarked as an engine testbed for the new RB.50, but any production aircraft would be at least three years away from entry into service.
E.24/43: Issued to Miles for undisclosed high-speed aircraft project.
Miles M.52
Specification E.24/43 for a jet-powered research plane to reach supersonic speeds was classified as Top Secret when it was drawn up. The contract, awarded to Miles Aircraft Ltd. in October 1943, was for an aeroplane capable of flying over 1,000 mph (1,600 km/h) in level flight and climb to 36,000 feet (11,000 m) in 1.5 minutes. The specification was intended counter French research, being carried out by the Leduc ramjet-powered aircraft, and to form the basis of the RAEs own High Speed Programme. No existing jet-powered aircraft in Britain had the kind of aerodynamic features to enable a serious study to be undertaken. Their round noses, thick wings and hinged elevators, gave them critical Mach numbers well below the speed of sound, and were less suitable for research into high subsonic speeds (in dives). The Supermarine Spitfire with its thin elliptical wings proved to be about the best aircraft for these early tests. RAE tests with the Spitfire in 1943 had proved that drag was the main factor to be addressed in high speed aircraft.
A huge number of advanced features are incorporated into the M.52 design, calling on the RAE’s knowledge of supersonic aerodynamics. With no other sources of information Miles turned to design data for stabilising projectiles. The design features a conical nose and sharp wing leading edges, as it was known that round-nosed projectiles could not be stabilised at supersonic speeds. The design uses very thin wings of biconvex section, proposed by Jakob Ackeret, for low drag. These wings are so thin that they are known to test pilots as 'Gillette' wings, named after the famous razor. The wingtips are clipped to keep them clear of the conical shock wave generated by the nose. The fuselage has the minimum cross-section possible around the engine with saddle fuel tanks over the engine. Another radical innovation is a power operated stabiliser, also known as the all-moving tail. Conventional control surfaces become ineffective at the high subsonic speeds due to the aerodynamic forces caused by the formation of shockwaves at the hinge and the rearward movement of the centre of pressure, which together can override the control forces applied mechanically by the pilot. The fuselage is cylindrical and constructed of high tensile steel with alloy covering. The pilot is housed in a small cockpit inside the shock cone in the nose, and in an emergency the entire nose can separated from the aircraft using explosive bolts. The M.52's design underwent many changes during development due to the uncertain nature of the task. The overseeing committee was concerned that the biconvex wing would not give sufficient altitude for testing the aircraft in a dive. The thin wing could be made thicker if required, or a section added to increase the span. As the project progressed an increase in total weight led to concerns that power would be insufficient and rocket assistance or extra fuel tanks were considered, as was high altitude air-launching from a bomber.
A Miles M.3B Falcon Six is planned to be fitted with a full size wooden model of the M.52 wing, test instrumentation and a new undercarriage to fly in late-1944.
Engines
Rolls-Royce RB.23 Welland
The RB.23 Welland is Britain's first production jet engine. It was designed by Frank Whittle's team at Power Jets Limited. Stanley Hooker joined the team from Rolls' supercharger division and added his experience in turbocompressor design. The RB.23 is a larger version of Whittle's original flying design, the Whittle Supercharger Type W.1, which flew in 1941 in the Gloster E. 28/37 experimental aircraft. The engine uses a single double-sided centrifugal compressor with the compressed air being taken off at several ports around the extreme outer edge of the compressor disk. It uses Whittle's reverse flow design, in which the flame cans (combustion chambers) are placed around the turbine to produce a shorter engine. This requires the heated air to flow forward before reversing its direction to pass through the single-stage axial-flow turbine. The impeller is 19 inches (480 mm) in diameter and there are ten flame cans. Air is bled from the compressor and fed into the inner portion of the turbine for cooling. The entire engine weighs about 850 lb (390 kg).
The first examples produced had serious problems with surging, in which the speed of the engine would suddenly increase out of control. Maurice Wilks eventually delivered a solution, by adding a set of 20-vane diffusers to the exhaust area. Also there were serious problems with the turbines failing due to heat. J.P. Herriot of the Air Inspection Department (A.I.D.) provided improved turbine materials, and then the engine achieved a 25-hour test at 1,250lbs thrust in November 1942. A flight-test took place on 9 August, 1942, fitted in the tail of a Vickers Wellington bomber. A flight-quality Welland was fitted to a Gloster G.40 and was flown by John Grierson on 1 March 1943. The ratings improved to 1,526lbs, and passed a run at 1,600lbs on 7 May, 1943. The prototype F.9/40 was later fitted with 1,700lbs engines and was flown by Michael Daunt on 24 July, 1943. The early production Wellands are rated at 1,700lbs with 180 hours between overhauls. Rolls-Royce has built a new factory at Barnoldswick to build its jet engines on behalf of Power Jets and its own products, hence the new RB designation.
Diameter: 43 in (1,098 mm)
Dry weight: 850 lb (386 kg)
Maximum thrust: 1,700lbs
Rolls-Royce RB.26 Derwent
The Rolls-Royce Derwent is essentially an improved version of the Rolls-Royce Welland. It was designed by a Rolls-Royce team and they dispensed with Whittle's reverse flow design, and instead designed an axial-flow design. This layout makes the engine longer but makes the gas flow simpler and improves reliability. Adding improved fuel and oil systems, the Derwent I entered production rated at 2,000lbs thrust. A 2,400lb thrust improved version entered bench testing in later 1943.
Length: 84 in (2,135 mm)
Diameter: 41.5 in (1,055 mm)
Dry weight: 975 lb (443 kg)
Compressor: Single-stage dual-entry centrifugal compressor with two-sided impeller
Combustors: 10 flow combustors with igniter plugs in chambers 3 and 10
Turbine: Single-stage axial flow with 54 blades
Oil system: 2.75 gal (12.5 L) capacity, circulation rate 215 gal/hr (976 L/hr), maximum inverted flying time 15 s
Maximum thrust:
120lbs (0.5 kN) at 6,000 rpm at idle.
2,000lbs (8.9 kN) at 16,500 rpm for take-off
1,550lbs (6.9 kN) at 15,000 rpm for cruise
Overall pressure ratio: 3.9:1
Fuel consumption:
470 lb/hr (215 kg/hr) at idle
1,820 lb/hr (830 kg/hr) at cruise power
2,360 lb/hr (1,070 kg/hr) at maximum power
Oil consumption: 0.125 gal/hr (0.57 L/hr)
Thrust-to-weight ratio: 2.1:1 (20.1 N/kg)
Rolls-Royce RB.50
The Rolls-Royce RB.50 is the company’s first propeller-turbine engine. The RB.50 is essentially a Derwent II turbojet engine with an additional turbine stage driving a reduction gearbox (designed by A. A. Rubbra) connected to a five-bladed Rotol propeller. The RB.50 ran for 633 hours on test during 1943, flight testing aboard a G.41 Meteor is planned for late 1944. The planned rating is 750shp + 1,250lbs residual thrust.
De Havlland H-1 Goblin
H-1 Goblin I 2,700lbs 1943
The de Havilland Goblin, originally the Halford H-1, is a turbojet engine designed by Frank Halford. The Goblin was the second British jet engine to fly, and the first to pass type tests and receive a Gas Turbine class type rating. Design of the engine was carried out by Frank Halford at his London consulting firm from April 1941. It is based on the basic design pioneered by Frank Whittle, using a centrifugal compressor providing compressed air to sixteen individual flame cans, from which the exhaust powered a single-stage axial turbine. Compared to Whittle designs, the H-1 uses 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 engine somewhat simpler than Whittle's designs, allowing one of the main bearings to be removed. The H-1 first ran on 13 April 1942, and quickly matured to produce its full design thrust within two months. It first flew on 5 March 1943 in the Gloster Meteor, and on 20 September in the de Havilland Vampire.
It was at this time that de Havilland purchased Halford's consultancy company and he became chairman of the de Havilland Engine Company. The H-1 was named Goblin.
Length: 107 in (2,718 mm)
Diameter: 50 in (1,270 mm)
Dry weight: 1,550 lb (703 kg)
Compressor: Single sided, centrifugal flow
Combustors: 16 chambers
Turbine: Single stage
Maximum thrust: 3,000lbs at 10,200 rpm
Overall pressure ratio: 3.3:1
Turbine inlet temperature: 790 °C
Fuel consumption: 3,720 lb/hr (465 imp.gal/hr) (1,687 kg/hr - 2,114 L/hr)
Specific fuel consumption: 1.3 lbs/lb/hr
Thrust-to-weight ratio: 1.9 lbs/lb
Armstrong Siddeley ASX
An axial flow jet engine that first ran in April 1943. The ASX is unique in layout. The inlet to the 14-stage compressor is placed near the middle of the engine, the air flowing forward as it is compressed. From there it feeds into 11 flame cans arranged around the outside of the compressor, flowing back past the inlet, and finally through the turbine. This layout allows the compressor and combustion areas to be folded together to make the engine shorter. The ASX should be flight tested, by fitting one into the bomb bay of a modified Avro Lancaster, in 1944.
Length: 13 ft 11 in (4,240 mm)
Diameter: 42 in (1,068 mm)
Dry weight: 1,900 lb (865 kg)
Compressor: Axial flow, 14-stage
Combustors: 11 chambers, Nimonic 75 steel.
Turbine: Two stage, axial flow
Maximum thrust: 2,600lbs at 8,000 rpm
Specific fuel consumption: 1.03 lb/lbf/hr
Thrust-to-weight ratio: 0.73:1
Thursday, April 18th 2024, 4:07am
Go to the top of the page
