General Electric I-A

I-A
Type	Turbojet
National origin	United States
Manufacturer	General Electric
First run	April 18, 1942^[1]
Developed from	Power Jets W.2B/23
Developed into	General Electric J31

The General Electric I-A was the first working jet engine manufactured in the United States, achieving its first run on April 18, 1942.

The engine was the result of receiving an imported Power Jets W.1X that was flown to the US from Britain in 1941, and the I-A itself was based on the design of the improved Power Jets W.2B, the plans of which were also received. Like these designs, the I-A engine was also of centrifugal design and was built by the General Electric (GE) company.

The I-A engine led directly to the first production US jet engine, the General Electric J31 which powered the first US jet aircraft, the Bell XP-59A.

Design and development

Front view of the preserved Power Jets W.1 at the Science Museum (London) The almost identical W.1X is preserved at the Smithsonian Institution, Washington DC

During the late 1930s/early 1940s, a small company in England, known as Power Jets, had been developing, through a series of prototypes, a gas turbine engine to provide aircraft jet propulsion. Power Jets had been started by a Frank Whittle, who had thought of the concept of a jet engine whilst he was a young flight cadet at RAF Cranwell.^[2] He applied for a patent for the engine in January, 1930, although he eventually allowed the patent to lapse.

Power Jets Ltd was formed in March 1936. Manufacture of key engine components was undertaken by the British Thomson-Houston Company (BTH), starting in June 1936. Testing of the first engine, the WU, to demonstrate the concept, commenced on April 12, 1937. Because of a shortage of funds at Power Jets, engine components were in short supply, so development proceeded at a very slow pace.

However, in the summer of 1939, shortly before war was declared, the Air Ministry suddenly realised that the jet engine was likely to become a viable means of propulsion. As a result, Power Jets received a contract for a flight engine on July 12, 1939. Shortly afterwards, a contract was placed with Gloster Aircraft Company to produce an experimental aircraft to demonstrate the engine.

In May 1941, the first British jet aircraft, Gloster E.28/39, made its maiden flight. It was powered by the 860 lbf thrust Power Jets W.1. Prior to this first flight another engine known as the W.1X had been used in the prototype aircraft for taxiing trials. This particular one-off engine had been assembled from a collection of spare parts and was not considered flightworthy.

After a visit to England mid-1941, General Henry H. Arnold was so impressed by flight demonstrations of the Gloster E.28/39 he had witnessed that he arranged for the Whittle W.1X turbojet engine to be flown in October 1941 to the U.S in the bomb bay of a USAAC Consolidated B-24 Liberator,^[3] along with drawings for the more powerful W.2B/23 engine and a small team of Power Jets engineers,^[4] so that the US could develop its own jet engine. As a result, General Electric received a contract from U.S Army Air Corps to build a turbojet based on the W.2B/23.^[5] General Electric's extensive experience in turbocharger production made them the natural choice for producing such engine.^[6] With utmost secrecy, in October 1941 a small dedicated GE team at Lynn, Massachusetts, began the intensive development of the first US jet engine. GE initially referred to their engine as the Type I.^[7] Engine component production was undertaken fairly openly, but the project reference "Type I Supercharger" was used to disguise the true application of the parts.^[8]

The aerodynamic design and many mechanical features of the Type I were identical to that of the W.2B/23. However, there were some major differences, principally with the design of the wheelcase, which was brought into line with the US practice of mounting engine accessories on the engine itself.^[9]

In November 1941, well before the Type I would become available for testing, General Electric started ground running of the Power Jets W.1X engine.^[10] This was the first jet engine to run on US soil, but more importantly GE gained valuable experience of testing a turbojet engine.

The production General Electric J31. The rear of the engine is at left of the picture.

On April 18, 1942, twenty-eight weeks after stateside work began, GE’s engineers successfully ran the first Type I engine. True, the unit stalled before full engine speed was obtained, but this reflected British experience with the W.2B.

With their vast experience of developing turbochargers, General Electric turned their expertise to improving the Type I. A modified version, the Type I-A, incorporating partitions in the blower casing to separate the air flow into each of the individual combustion chambers at the suggestion of Whittle,^[11] began testing in May 18, 1942, and developed a thrust of 1,250 lbf, at an overall pressure ratio of 3:1.

P-59A Airacomet with the short-lived red outlined National markings (June 1943 to September 1943).

On October 1, 1942, a Bell XP-59A aircraft, powered by two 1,250 lbf thrust I-A turbojet engines, made its first flight at the Muroc Army Air Field in California. Further engine developments produced a 1,400 lbf thrust engine, known as the I-14, which was used to propel the service test YP-59A aircraft.

Ultimately, General Electric found they could produce a thrust of 1,610 lbf from a package the same size and weight as the I-A, which they called the I-16.^[12] Later, when the Bell P-59 went into production, the aircraft was fitted with General Electric J31’s, which was the USAAF designation for the I-16.

Meanwhile, Power Jets continued to develop the W.2B, initially with the help of the Rover Company. On April 1, 1943, Rolls-Royce took responsibility for developing the engine, and it went into small-scale production as the 1,600 lbf thrust Rolls-Royce Welland I in October, 1943. The Gloster Meteor I fighter, which entered RAF service in July, 1944, was powered by the Welland I.

Variants

Type I

Initial design based on W.1X. Incorporated automatic control system and forged Hastelloy B turbine blades. First run on 18th April 1942. Ran hot.

Type I-A

Revised design incorporating partitions in blower casing at suggestion of Whittle.^[13]

Engines on display

The W.1X is on display at the Smithsonian Institution, Washington DC.^[14]

Applications

Bell XP-59A

Survivors

Specifications (General Electric I-A)

General characteristics

Type: Centrifugal compressor turbojet, single shaft
Length: 70.5 in (1791mm)
Diameter: 44 in (1118mm)
Dry weight: 780lb (354kg)^[15]

Components

Compressor: Single-stage double-sided centrifugal
Combustors: 10 reverse-flow can
Turbine: Single-stage axial
Fuel type: Kerosene

Performance

Maximum thrust: 1250lbf (5.56kN)
Overall pressure ratio: 3:1
Thrust-to-weight ratio: 1.6

References

General Electric aircraft engines

Turbojets	CJ610 CJ805 GE1 GE4/J5P J31 J33 J35 J47 J73 J79 J85 J87 YJ93 J97 YJ101

Turbofans	CF6 CF34 CF700 CFE738† CFM56/F108† CJ805-23 F101 F110 F118 YF120 F136† F404/F412/RM12 F414 GE90 GEnx GP7000† HF120† LEAP† Passport TF34 TF39 RM12

Turboprops/Turboshafts	GE27 GE36 GE38-1B GE93 H80 T31 T58/CT58 T64/CT64 T407 T408 T700/CT7

Aeroderivative gas turbine engines	LM500 LM1500 LM1600 LM2500 LM6000 LMS100 LV100†

† Joint development aeroengines

United States military gas turbine aircraft engine designation system

Turbojets	J30 J31 J32 J33 J34 J35 J36 J37 XJ38 J39 J40 XJ41 J42 J43 J44 J45 J46 J47 J48 XJ49 J51 J52 J53 J54 J55 J56 J57 J58 J59 J60 J61 J63 J65 J67 J69 J71 J73 J75 J79 J81 J83 J85 J87 J89 J91 YJ93 J95 J97 J99 J100 YJ101 J102 J400 J401 J402 J403 J700

Turboprops/ Turboshafts	T30 T31 T33 T34 T35 T36 T37 T38 T39 T40 T41 T42 T43 T44 T45 T46 T47 T48 T49 T50 T51 T52 T53 T54 T55 T56 T57 T58 T60 T61 T62 T63 T64 T65 T66 T67 T68 T69 T70 T71 T72 T73 T74 T76 T78 T80 T100 T101 T400 T405 T406 T407 T408 T700 T701 T702 T703 T706 T708 T800

Turbofans	TF30 TF31 TF32 TF33 TF34 TF35 TF37 TF39 TF41 F100 F101 F102 F103 F104 F105 F106 F107 F108 F109 F110 F112 F113 F117 F118 F119 YF120 F121 F122 F124 F125 F126 F127 F128 F129 F135 F136 F137 F138 F400 F401 F402 F404 F405 F408 F412 F414 F415

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