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A Brief History of Aircraft Engine Development at General Electric

John C. Blanton * and David C. Wisler.† GE Aviation, Cincinnati OH 45215 USA

General Electric is a company best known for light bulbs, appliances, and catchy TV jingles, but the aviation industry knows GE as the world’s leading producer of aircraft jet propulsion engines. Among other industry milestones, GE produced America's first jet engine, developed the first turboprop engine, the first variable stator engine, the first turbojet engine to power flight at two times the speed of sound, and the world's first high bypass turbofan engine to enter service. GE’s roots in the aviation industry started in the early part of the 20th century with the development and large-scale production of aircraft engine turbo superchargers. Success in this endeavor, coupled with the fact that GE was not a current supplier of aircraft engines to the US military, led General Hap Arnold to select a GE team in Lynn MA to produce a US version of Sir Frank Whittle’s British jet engine that first flew in a British Gloster in May 1941. The first US jet flight, the Bell XP-59A powered by the GE I-A centrifugal turbojet, followed in October 1942. This milestone event launched GE into the aircraft engine industry, where it has for decades maintained a leading position in the often turbulent world of designing, developing, and producing jet and turboshaft propulsion systems for both military and civil applications. This paper highlights the significant events of the early GE history and the people who had a hand in them.

Introduction This paper traces the history of the General Electric Company’s involvement in the design, development,

production, and service of aircraft jet propulsion engines. A complete documentation of this history in one technical paper would be impossible, and the reader is referred to several excellent books written solely on this subject. Two of them [1, 2] served as primary sources for this paper. The purpose of this paper is to summarize the important milestones in this history, particularly in the early years, to give a perspective of how the GE Company became involved in this part of the aviation business. Only brief mention is made of events of the last 30 years or so in order to keep the focus on the more historical developments.

GE Early Aviation History The General Electric Company is one of the world’s best-recognized and most-respected corporate organizations

[3]. The company was created in 1892 with the merger of the Edison General Electric Company and the Thomson-Houston Company. Charles A. Coffin (Fig. 1), president of the Thomson-Houston Company, became the first President of GE and led the company for 30 years. The primary GE manufacturing locations were in Schenectady NY and Lynn MA. The familiar GE logo (Fig. 2) was introduced in 1898 and remains today one of the world’s most-recognized corporate symbols. GE was one of the original 12 company stocks of the Dow-Jones Industrial Average in 1896, and is the only one of the 12 that exists today.

In the early days the core businesses of GE serviced the fledgling electric power generation, distribution, and consumer industries. GE was (and remains today) a leading manufacturer and innovator in electric generators and motors, power plant equipment, electric distribution gear, and consumer appliances. A key contributor to the early and the continued success for GE was a significant investment in research and development. The GE General Engineering Laboratory (GEL) and the campus-like GE Research Laboratory, both located in Schenectady NY,

* Consulting Engineer, Advanced Engineering Programs, Cincinnati OH, Associate Fellow AIAA. † Manager - University Programs, Advanced Engineering Programs, Cincinnati OH, Associate Fellow AIAA.

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 8 - 11 July 2007, Cincinnati, OH

AIAA 2007-5339

Copyright © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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became models of industry. These organizations later merged to become the GE Research and Development Center (now the Global Research Center) which today remains one of the world’s preeminent centers of scientific research.

In 1903 a young Cornell University graduate, Dr. Sanford A. Moss (Fig. 3), joined the GE company in Lynn MA. While at Cornell, Dr. Moss studied under the tutelage of Dr. William F. Durand, who in 1915 became the first civilian chair of the National Advisory Committee for Aeronautics (NACA), and who has been called the “Dean of American Engineering”. Dr. Moss published his Ph.D. dissertation on his theoretical and experimental work on the design and development of a successful gas turbine engine, one of first (if not the first) to produce positive net power output. At GE, Dr. Moss became involved in technologies applied to the new field of aviation power. He led the development and the application of turbo superchargers (Fig. 4 and 5) to enable airplanes to perform at high altitudes, and he has been called the “Father of the Turbocharger”. GE became the world leader in the production of turbochargers, supplying 370,000+ units over a period of 30+ years lasting into the 1940’s. This experience became the entry of GE into the aviation propulsion industry, and was an important factor in events to follow. Dr. Moss retired from GE in 1938, was awarded the prestigious Collier Trophy for his turbocharger work in 1940, and in 1976 he was enshrined into the National Aviation Hall of Fame.

The First U.S. TurboJet Engine In May 1941 General Henry H. “Hap” Arnold of the U.S. Army Air Corps (Fig. 6) was invited by the British Air

Ministry to witness early test flights of the Gloster E-28/39 aircraft (Fig. 7) powered by the Whittle W1 turbojet engine (Fig. 8). Upon returning to Washington he commissioned a crash program to leverage this new technology for use by the U.S. Army Air Corps. His leadership team quickly selected GE as the preferred contractor for two very compelling reasons. The first was that the Army Air Corps did not want to distract its major airplane engine suppliers (Pratt & Whitney and Wright Aero) from their current work. There was also legitimate concern that these suppliers might not be enthusiastic at being asked to work on technology that could make their current products obsolete. The second was that GE, because it was already involved in the design and production of turbochargers and had gas-turbine development programs underway, had the intellectual resources and infrastructure to take on this ambitious project. General Arnold contacted R.C. Muir, Vice President of Engineering for GE, and requested

Figure 1

Charles A. Coffin First President of the General

Electric Company (1892-1922)

Figure 2

GE Company Logo in 1898

Figure 3

Sanford A. Moss in 1894 at age 22

Figure 4

Sanford A. Moss later in his career holding a turbo supercharger rotor

Figure 5

General James (Jimmy) Doolittle and Sanford Moss examine

GE Type B turbo supercharger

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that he identify and dispatch an engineering representative to Britain to work with the British Air Ministry on the potential transfer of the Whittle engine technology to the U.S. As it happened, GE already had D. Roy Shoults in Britain supporting customers of GE-supplied turbo superchargers installed on B-17 bombers. Mr. Shoults was already aware of some aspects of the Whittle engine and of the British Air Ministry progress. A flurry of meetings, demonstrations, and studies culminated in a top-secret meeting in Washington D.C. on 04 September 1941 where General Arnold stated “Consult all you wish and arrive at any decision you please, as long as General Electric accepts the contract to build 15 of them.” GE accepted the terms of the offer. The Bell Aircraft Company in Buffalo NY was selected to provide three airframes.

A small select team was assembled at the GE Lynn River Works under the leadership of Donald F. “Truly” Warner to execute the top-secret jet engine project in a “skunk works” environment. The team had access to some of the drawings of the Whittle W1 engine, as well as to an actual engine, but was handicapped by lack of detail and/or missing information. In a remarkable feat of engineering, innovation, and creativity that overcame initial stall problems, the team had the first GE version of the W1, dubbed the GE “I-A” (Fig. 9), to test on 14 April 1942, about 7 months from the date of the Washington meeting. Early testing occurred in a test cell known as “Fort Knox”. Security was so tight that factory workers outside the small development team believed that advanced turbo supercharger designs were being tested. In June 1942 Frank Whittle, traveling in secrecy and under an assumed name, arrived in Lynn and stayed several weeks to observe and provide consultation to the development team.

In September 1942 the first GE I-A flight engines and the Bell XP-59A Airacomet aircraft were shipped across the country to Murdoc Dry Lake CA (now Edwards Air Force Base) in preparation for the first U.S. jet-powered flight (Fig. 10). Absolute secrecy continued to be the order of the day, to the extreme that the Bell airframe was fitted with a dummy propeller in an attempt to mislead casual observers and potential enemy agents (Fig. 11). The historic first flight of the XP-59A, powered by two GE I-A engines, took place on 02 October 1942 with test pilot Bob Stanley in the cockpit, and the United States officially entered the Jet Age. A U.S. Army officer witnessing the flight, seeing no propeller, was heard to ask “How does the damn thing go?”

The GE I-A jet engine, like the Whittle W1, featured a double-inlet centrifugal compressor rotor powered by a close-coupled, single-stage, un-cooled turbine (Fig. 12). The combustion system consisted of 10 individual chambers in a reverse-flow arrangement designed to increase residence time and minimize the rotor length. The thrust produced was 1250 lbs as compared to approximately 850 lbs produced by the first Whittle W1 flight engine (and also by the von O’Hain engines that powered the first-ever jet-powered flight in Germany on 27 August 1939).

Figure 6

U.S. Army Air Corps General Henry H. “Hap” Arnold

Figure 7

Gloster E-28/39 jet-powered aircraft

Figure 8 Frank Whittle and the

W-1 jet engine

Figure 9

General Electric I-A The First U.S. Jet Engine

Figure 10

Bell Aircraft XP-59A First U.S. Jet Plane

Figure 11

XP-59A with Dummy Propeller to Mislead

Potential Agents

Figure 12

Cutaway GE I-A (GE Propulsion Museum)

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Continued Development of Centrifugal TurboJet Engines The early flight tests of jet-powered aircraft clearly demonstrated the potential superiority of the new propulsion

system, but higher-thrust engines were required to realize this promise. The GE designers rapidly made improvements to the basic I-A design to increase thrust, efficiency, reliability, and operability. New technologies in the areas of aerodynamics, materials, and controls enabled the rapid introduction of engine models with higher and higher thrust levels.

The GE models I-14 and I-16 (the latter was designated the J-31 by the U.S. military) produced thrust levels of 1400 and 1650 lbs thrust, respectively. These engines were flight-tested in the upgraded YP-59A in 1943-44. The J-31 was the first GE production engine with 241 units delivered (Fig. 13 and 14).

In June 1943 GE designers, under the direction of Dale Streid, began work on a much more powerful centrifugal jet engine, one targeted to power the Lockheed P-80 (Fig. 15). This aircraft, the first operational U.S. jet fighter, was designed by the legendary Clarence “Kelly” Johnson. The new engine, GE model I-40, produced 4200 lbs thrust in the first ground test in January 1944. The first flight in the XP-80 airframe occurred on 10 June 1944, one year after the start of the engine development.

The I-40 (Fig. 16), better known as the J33 (U.S. military designation), featured many improvements over the first-generation centrifugal jet engines. One of the more significant improvements was the replacement of the reverse-flow combustion chambers with more-conventional straight-through chambers. This significantly reduced the diameter of the engine (at the expense of a somewhat greater rotor length), which is very important to the airframe designer. The J33 also featured independently supported compressor and turbine rotors connected by a flex coupling and a new low-pressure fuel atomization system developed by GE’s Tony Nerad.

In a production run of 15 years, Lockheed produced 917 P-80As, P-80Bs, and the two-seat trainer T-33s. Almost 7000 J33 turbojets were produced for these and other aircraft. Unfortunately, GE only produced 300 of these J33 engines due to limited manufacturing capacity in Lynn MA. Most of the rest of the production was licensed to the Allison Division of General Motors in Indianapolis IN.

In 1943 the famous British engine designer Sir Stanley Hooker (later to head the Rolls Royce engine company) visited the GE Lynn facility and received a briefing about the J33. He was very surprised to find that the U.S. engine development efforts had so quickly eclipsed the efforts in Britain and resolved upon his return to see that Britain also develop a 4000-lb thrust turbojet. The Rolls-Royce RB41 Nene was the result of this resolve. In 1947 Rolls Royce licensed production of the Nene to the Pratt Whitney Company, which began producing it as the company’s first turbojet engine, the J42. Rolls Royce also allowed the Russians to have the Nene and they began producing their version as the RD45 turbojet engine for the MIG-15 fighter. The Russians eventually produced 39,000 units and passed on the technology to China where the engine remained in production until 1979.

Axial Turbojet Development During the same time period that the GE team in Lynn was involved in the top-secret centrifugal turbojet

development projects, another GE team at the General Engineering Laboratory in Schenectady NY was designing aircraft gas turbine systems based upon the newer axial-flow compression technology supported by the NACA. (GE engineers Alan Howard, Glenn Warren, and Bruce Buckland were primary contributors to this program.) The initial effort was aimed at the development of a turboprop engine for the proposed Convair XP-81 fighter aircraft (Fig. 17). This engine, designated the TG-100 (military designation T31), produced 2200 shp and 630 lb thrust and featured a 14-stage compressor and a single turbine stage that drove both the compressor and the propeller gearbox. Although a T31-powered XP-81 did first fly in 1945 and go through a two-year flight-test program, the US Army Air Corps

Figure 13

GE I-16 (J31) Installation on the Bell YP-59A

Figure 14

GE I-16 (J31) at the U.S. Air Force Museum

Figure 15

Lockheed P-80 Shooting Star

Figure 16

GE I-40 (J33) Jet Engine (GE Propulsion Museum)

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(US Air Force after 1947) had begun to lose interest in turboprop development and by 1949 had cancelled all programs.

The new interest of the US Air Force was, of course, axial turbojets. In May 1943 GE was asked undertake the development of a 4000-lb thrust axial turbojet (note this program was in parallel to the J33 centrifugal turbojet program). The GE design was designated the TG-180 and drew heavily from the design and development experience from the TG-100 axial turboprop. The TG-180 (military designation J35) featured an 11-stage compressor and a single-stage turbine and had an engine pressure ratio (EPR) of 4 (see Figs. 18 and 19). The first engine to test (FETT) was in April 1944 and met performance objectives although it was two more years before the engine was able to pass the 150-hr Military Qualification Test. The first J35 tested in flight was in November 1945 on a B-29 flying test bed (FTB) aircraft, and the first J35-powered aircraft to fly was the elegant Boeing XB-47 swept-wing stratojet bomber prototype (see Fig. 20) in Dec 1947.

The J35 turbojet remained in production until 1955, and overall approximately 15,000 engines were produced. As with the J33, the vast majority of these were again built by the Allison Division of General Motors, which was awarded the production and development contract in Sep 1947. The final versions of the engine, produced 5600 lb dry thrust (J35-A-29) and 7400 lb thrust with afterburning (J35-A-35). GE and Allison versions of the J35 powered aircraft including the B47, P84, YB-49A (flying wing), P89, B46, and B48.

GE Becomes a Major Producer of Jet Engines The licensing of the large-scale production of the J33 and J35 turbojets to Allison was a major source of

annoyance and frustration to many GE managers and engineers who had contributed to the design and development efforts. The lack of production capacity at the Lynn River Works was an important factor. There were, however, other forces at work. Some GE Company officers felt that GE should extricate itself from business in the military sector and focus on commercial manufacturing. The next major step in the evolution of jet engine development at GE resolved these issues.

In July 1945, Harold Kelsey was named the Manager of the new Aircraft Gas Turbine Division of GE. Under his direction GE dropped all work on centrifugal turbojets and concentrated solely on axial turbojet development. In Mar 1946, Neil Burgess was named leader of the project team for the TG-190 (J47), a growth of the J35 (see Fig. 21). A “zero stage” was added to the compressor, increasing the airflow and EPR, and improvements were made to the combustor and turbine. The FETT was in June 1947, the first flight test on the B-29 FTB was in Apr 1948, and the first J47-powered flight on an XF-46 was in May 1948. The first model (TG-190A or J47-GE-1) had a dry thrust rating of 4850 lb, and was delivered to the US Army Air Corps in Sep 1947. GE began production of J47 engines in Building 29 of the Lynn River Works in the summer of 1948. At the same time, a search was underway for new manufacturing facilities to better position GE for full-scale production of the J47 and other future aircraft engine products.

In Oct 1948 GE took occupancy of a large portion of the US government-owned facility in Lockland OH (see Fig. 22), a northern suburb of Cincinnati. The facility had been built in the early 1940’s and used by the Wright Aeronautical Corp to built piston engines for WW II aircraft, and had been vacant for two years. Among the

Figure 17

Convair XP-81

Figure 18

Cross-section of GE TG-180 (J35) Turbojet Engine

Figure 19

Cutaway GE TG-180 (J35) Jet Engine (GE Propulsion Museum)

Figure 20

Boeing XB-47 prototype in flight

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advantages that the site offered were proximity to Wright Field in Dayton OH, an excellent local labor pool, a large manufacturing space including the largest “under roof” structure in the world, and 40 engine test cells (see Fig. 23). The GE Lockland (now Evendale) Plant was formally opened in Feb 1949 with Orville Wright (then in his 70’s) the guest of honor at the ceremonies. By Nov 1949 the entire J47 operation had been relocated to Lockland.

The J47 was in production until 1956 with over 36,000 engines produced, making the program the largest in U.S. history (see Fig. 24). At its peak in 1953-54 during the Korean conflict, the production rate reached 975 units per month. Aviation Week, in a 1947 article, called the J47 “the most widely specified American jet power plant”. Aircraft powered by the J47 include the B-45, B-47, F-86, KB-50J, KC-97, XB-29G, XB-51, XF-87, and the XF-91. The J47 was the first jet engine certified for commercial operation by the Civil Aeronautics Administration (CAA). The thrust level of the engine was increased through incremental improvements to a level of approximately 6000 lb dry and 7600 lb with afterburning. Among the important technologies developed by the J47 team were an advanced engine anti-ice system and an electronically-controlled afterburner.

The success and experiences of the J47 program (Fig. 25) established GE as a major producer as well as designer/developer of jet engines. No longer did the old saying “developed at General Electric, produced at General Motors” apply.

Axial Turbojet Improvements The J79 - The First Mach 2 Engine

In mid-1949, when the J47 started into full-scale production, GE started work on a significant growth version. This engine, initially designated the J47-GE-21 but eventually changed to the J73, incorporated several advanced features that enabled a 50 percent thrust growth (9000 lb dry) over the J47. The J73 incorporated GE’s first two-stage turbine, first variable inlet guide vane (IGV), first “cannular” combustion system, and the first use of titanium alloy (see Fig. 26). The J73 was tested and in mid-1950 through 1951 and a relatively moderate number (870) were produced through 1955 for the North American F86H fighter.

Even with the significant advancements that were incorporated, the J73 became rapidly obsolete in the face of the next generation of turbojets. In the early 1950’s it was apparent that turbojets operating at EPR levels of 12 or more would be required. The current generation of fixed-geometry, single-spool compressors were limited by operability (compressor stall and/or choking) to a pressure ratio of approximately 6, and with a variable IGV (e.g. the J73) could reach 7+. Two new technologies were under consideration that would permit axial compressors to overcome the operability issues and to reach higher design pressure ratios. The first was expanded use of variable stator vanes (VSVs), similar to the variable IGV in the J73, in the forward compressor stages. The second was to subdivide the compressor rotor into two or more sections (spools) that could operate at different speeds, each driven by its own turbine. Each approach has advantages and disadvantages, and at the time there was very little practical experience to draw from in concluding which approach should be followed. GE set up two teams to perform preliminary design studies and develop performance and cost models. The VSV team was led by Gerhard Neumann, and the two-spool team by Dr. Chapman Walker (see Fig. 27). Based upon the model results reported by the teams at a famous offsite review meeting in French Lick IN culminating on Halloween 1982, GE selected the variable-geometry approach. The decision was not made without controversy. Although most of the quantitative data generated during the detailed studies favored the VSV approach, the six individual design task groups all expressed a preference for the two-spool approach. In addition, GE’s competitor Pratt Whitney had already committed to the two-spool approach in their very successful J57 turbojet design.

In Sep 1953, after further study and intense contract negotiations with the USAF, GE launched the J79 project. Considerable technology development was already available from the GOL-1590 demonstrator engine program

Figure 21

Cutaway GE TG-190 (J47) Jet Engine (GE Propulsion

Museum)

Figure 22

GE Lockland (now Evendale) OH Plant

Figure 23

GE Lockland Plant Test Cells

Figure 24

J47 Production in Lockland Plant

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headed by Neumann. The demonstration compressor for this engine had gone to test earlier in the year and produced astounding performance results. FETT for the GOL-1590 demonstrator engine was in Dec 1953, during which the engine disintegrated at full speed due to a faulty engine mount bracket (a test equipment part). The setback was only minor however, and within two months a replacement engine had completed six highly successful tests. June 1954 marked the FETT for the J79-GE-1 engine, the world’s first production Mach 2 jet engine. It featured a 17-stage compressor with six VSV stages (see Figs. 28-30) and a three-stage turbine, with a ten-chamber “cannular” combustor. The installed engine weight was less than that of the J47. It achieved an EPR of 12.5 and produced 10,000 lb thrust dry and 16,000 lb thrust in afterburner (the highest augmentation ratio achieved to that time). The first flight test occurred in May 1955 on a modified North American B-45 Tornado bomber, where the J79 was installed in the bomb bay and lowered into the air stream during flight. In Dec 1955 the first J79-powered flight took place using a modified Douglas XF-4D with legendary GE test pilot Roy Pryor at the controls.

The US Air Force selected versions of the J79 for the 4-engine Convair B-58 “Hustler” (first flight Nov 1956) and the Kelly Johnson-designed single-engine Lockheed F-104 “Starfighter” (first flight Feb 1956), both Mach 2 combat aircraft. The 1958 Collier Trophy was awarded to the Lockheed-GE team for the F-104/J79 system (see Fig. 31). The US Navy later selected the J79 for the 2-engine McDonnell F-4 “Phantom” (first flight May 1958). Over 17,000 J79 units were produced, all in the Lockland Plant, through 1979 when production finally ended. The majority of the J79s produced were for the F-4.

Figure 25

J47-Powered Aircraft at GE Flight Test Center (Edwards AFB) in

1950’s

Figure 26

Cutaway J73

Figure 27 Dr. Chapman Walker and Gerhard

Neumann

Figure 28

Variable Stator Vans (VSVs)

Figure 29

Cutaway J79 Compressor With VSV Stages (GE Museum)

Figure 30

Cutaway J79 (GE Museum)

Figure 31

1958 Collier Trophy Presentation for F-104/J79 (from left to right)

Major Walter W. Irwin, Lt. Col. Howard C. Johnson, Vice President Richard M. Nixon,

Gerhard Neumann, Neil Burgess, C. L. “Kelly” Johnson

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Later, non-afterburning civil versions of the J79 were also developed, becoming GE’s first commercial jet engines to enter service. The CJ805-3 (see Fig. 32) was selected to power the 4-engine Convair 880 airliner (EIS 1960), and the CJ805-23 (see Fig. 33) the Convair 990 (EIS 1961). The CJ805-23 became the world’s first turbofan to enter airline service by incorporating a unique aft-fan arrangement (see Fig. 34). The fan and the turbine that powers it are one single disk, with the fan and turbine blades combined into a single structure (called a “blucket”) with a integral shroud (see Fig. 35). This simple turbofan design was compact, lightweight, and cost-effective, but was yielded inferior performance to a front turbofan that provides supercharging of the airflow entering the compressor.

The J93 - Mach 3 Engine

In 1954, responding to the demands brought on by the “Cold War”, the US Air Force published General Operational Requirements for a project known as “Weapon System 110A” to develop and field a supersonic intercontinental bomber. This program eventually led to the development of the XB-70, powered by 6 GE J93 engines, capable of Mach 3+ operation. The contract for the engine development was awarded to GE in May 1957. Up to that time GE had designated the engine the J79-X279E. FETT for the first prototype engine, designated the J93-GE-1, occurred in Sep 1958, and the engine first ran at Mach 3 conditions in the Evendale Ram Test Facility in Jul 1959.

In Dec 1957 North American was named as the winner of the competition to develop the 110A bomber, now designated the B-70 Valkyrie (Fig. 36).

The USAF authorized development of the flight engine model, the J93-GE-3, in Mar 1958. A new design feature of this model was the incorporation of active cooling of the first-stage turbine rotor blades. The GE-developed STEM (Shaped Tube Electrolytic Machining) process was used to produce the cooling channels in the blades. FETT for the J93-GE-3 occurred in Jul 1959. It was the first operational turbine engine in America to run with air-cooled turbine blades. The engine design was a pure turbojet with an 11-stage compressor and 2-stage turbine, and featured an annular combustor. All 11 compressor stages and the IGV were variable, and the front three stages and IGV were scheduled independent from the rear stages. A fully-modulating afterburner and an exhaust nozzle with variable throat and exit areas were used to produce a maximum take-off thrust of 28000 lb (Fig. 37).

The first flight of the B-70 Valkyrie bomber, equipped with 6 J93-GE-3 engines, occurred in Sep 1964. The plane first flew at Mach 3 in Oct 1965. By the time the plane was flying the USAF had cancelled the B-70 program and decided to build only two prototype planes, the XB-70A. The engines were now designated the YJ93-GE-3. In Jun 1966 the second prototype crashed after a mid-air collision with an F-104 chase plane during a GE-staged photo shoot. The final flight of the remaining prototype was in Feb 1969, when it was ferried to Wright-Patterson AFB to be put on display at the AF Museum.

Figure 32

CJ805-3B (note thrust reverser and noise suppressor)

Figure 33 CJ805-23B (GE Museum)

Figure 34

Aft Turbofan Engine Schematic

Figure 35

Aft Turbofan “Blucket”

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The GE4 - The Most Powerful Pure Turbojet Ever Built

The US Supersonic Transport (SST) program was launched in 1963 with much fanfare. The program was managed by the US Federal Aviation Administration (FAA). The proposed GE engine, the GE4, was designed using experience gained from the J93 engine for the B-70. After an intense three-year competition, the team of Boeing and GE were announced as the winner of the contract to build the US SST, the Boeing 2707 (Fig. 38). The GE4 (Fig. 39 and 40) was the largest pure afterburning turbojet engine that had ever been designed, with a rated sea-level thrust of 68,600 lb. Facilities built to support this program included a new test cell in Evendale capable of 80000 ft altitude, Mach 3 conditions. FETT was in Mar 1968 and the engine generated a maximum thrust of 69,900 lb.

In Mar 1971, bowing to pressures exerted by environmental groups, the US Senate voted 49-48 to cancel the US SST program.

Small Engine Development When the GE Aircraft Engine Division opened operations in Ohio in 1949, a small group remained in Lynn MA

as part of the Aircraft Accessory Turbine Department. In Jan 1953 this group submitted a proposal to the US Navy for an 800 shp turboshaft engine for helicopter applications. The design work for this new engine, designated the T58-GE-2, started in Jun 1953 and was completed in Mar 1954. During this time the GE Aircraft Engine Division was reorganized to create the Small Aircraft Engine Department in Lynn. The final T58-GE-2 design promised 1050 shp and a weight of only 250 lb, and was referred to as the “Baby Gas Turbine”. The engine featured a 10-stage axial compressor scaled from the J47 design with three stages of VSVs, a two-stage gas generator turbine, a single-stage power turbine, and the first GE annular combustor (see Fig. 41-43). The FETT occurred in Apr 1955 and the first flight on a Sikorsky HSS-1F helicopter in Jan 1957. Various versions of the T58 were produced over the subsequent years to power a number of rotorcraft applications. The T58 production line remained open until 1984 with over 6300 units produced. The T58 was the first GE engine to be globally licensed (to DeHavilland Engines) and an additional 2200 units have been produced under license in the UK, Japan, and Italy. It gave GE its first contract experience with the US Navy, starting a successful relationship that continues to this day. Most importantly, the T58 verified that a very small engine could be designed and manufactured to the same standards as a large engine.

Figure 36

North American XB-70

Figure 37

XJ93-GE-3

Figure 38

Mockup of Boeing 2707

Figure 39

GE4 on Test Stand in Peebles OH

Figure 40 GE4 in Afterburner Test

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The Small Aircraft Engine Department began developing the “big brother” of the T58 in 1954. Marketing studies indicated the need for a turboshaft engine in the 2500 shp class. An ambitious design EPR of 12.5 and airflow of 25 lb/sec were chosen. Development of the new engine, designated the T64, proceeded at a relatively leisurely pace due to the uncertainty in the ultimate naval application. The engine featured a 14-stage titanium axial compressor with four stages of VSVs, a two-stage gas generator and power turbines, and an annular combustor. It has been in continuous production since 1964 with over 3000 units delivered, principally for the CH-53 helicopter. The engine rating has grown to 4750 shp.

The J85 - High Thrust-Weight Jet Engine

In 1954 the Small Aircraft Engine Department proposed the development of a new “small” axial turbojet engine with very high thrust-to-weight ratio. The engine, designated the MX-2273 by GE and the X104 by the USAF, was to generate 2500 lb, have an EPR of 7, weigh just 250 lb and have a diameter of 12 inches. The original design proposed a six-stage compressor, an annular combustor (based on the T58), a two-stage uncooled turbine and two main rotor bearings. The USAF interest in the engine was for the McDonnell GAM-72 Green Quail target drone and other proposed small vehicles. As the program proceeded, both unmanned and manned and both dry and afterburning versions of the engine (now called the J85) were developed. Although the J85 was eventually used in a wide number of small-engine applications, the vast majority found their way as pairs into the Northtrop N-156 airframe. This versatile aircraft, which first flew in Apr 1959, was configured as a single-seat fighter (F-5) or a two-seat trainer (T-38). In a production period lasting over 30 years (ending in 1988) over 16000 units were produced (Fig. 44). The final production model, the J85-GE-21 was rated at 5000 lb thrust (wet).

Two non-afterburning commercial versions of the J85 were also produced. The CJ610 (the CJ designation stands for “commercial jet”), rated at approximately 3000 lb thrust, was used on the Learjet and several other business-jet applications. FETT for the CJ610 was Apr 1960 and FAA certification was granted Jan 1962. About 2100 CJ610 engines were produced through 1984 (Fig. 45).

The other commercial J85 was a bit more unique. The CF700 added an aft turbofan rotor, similar in function to that developed for the J79-derivative CJ805-23B. This increased the thrust by approximately 50 per cent up to 4500 lb. The CF700 powered the Dassault Falcon series of business jets. About 1200 CF700 engines were produced through 1982 (Fig 46).

Figure 41

T58 Turboshaft (“Baby Gas Turbine”) (GE Propulsion Museum)

Figure 42

T58 Turboshaft Compressor (GE Propulsion Museum)

Figure 43

T58 Turboshaft Combustor (GE Propulsion Museum)

Figure 44

J85 Turbojet

Figure 45

CJ610 Commercial Turbojet

Figure 46

CF700 Commercial Turbofan

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High-Bypass Turbofans The TF39 – The First High-Bypass Turbofan

The development of the TF39 was a landmark achievement both for GE and for the aircraft engine industry. The beginnings of the TF39 program lie in GE’s participation in the US Air Force Project Forecast, which started in 1962. The results of these studies led to the definition of the requirements for a large, high-bypass ratio turbofan engine for the Air Force CXX (later designated the C-5) transport program. GE’s proposal for this program was based upon a strong set of technologies from a number of prior and ongoing programs such as the GE1 demonstrator, the XV5 lift fan, and the J93 turbojet. GE proposed a turbofan with an 8:1 bypass ratio, an unheard-of level at that time, with a 2500ºF turbine inlet temperature and 25:1 engine pressure ratio. The proposal effort produced over 500 volumes that required a semi-trailer to deliver to Wright Field. The contract for $459 million, awarded to GE in Aug 1965 to deliver 440 engines, was the largest the company had ever received.

The FETT ran in Dec 1965 and the first flight test was in Jun 1967 using a Boeing B-52 FTB. The first flight of the C-5 was in Apr 1969 and GE completed delivery of 464 TF39 engines in 1971. Four of the giant engines, each providing 40,000 lb take-off thrust, powered the Lockheed C-5 Galaxy air transport (see Fig. 47). The TF39 design (see Fig. 48) featured a unique 1.5-stage front fan design incorporating a booster stage in front of the 100-inch diameter main fan, driven by a 6-stage low-pressure turbine. The engine core featured a 16-stage axial compressor, annular combustor, and a 2-stage turbine with film-cooled first-stage blades. The sea-level sfc (specific fuel consumption) of the engines was 0.315 lb/hr of fuel per lb thrust, a level less than half of the most efficient engines of the day.

The CF6 - GE Re-enters the Commercial Engine Business

As the decade of the 1960’s drew to a close, GE was virtually shut out of the commercial jet engine business. The J79-derived CJ805 engines entered limited service on the Convair 880 and 990 at the beginning of the decade but those aircraft were not a great commercial success. GE did not have a product offering for the popular Boeing 707, 727, and 737 or the Douglas DC-8 and DC-9. When Boeing launched the 747 in 1965 it required very large (40K lb thrust or higher) turbofan engines. GE was already in the development program for the TF39 and considered offering a derivative, but eventually chose to decline.

In 1967 GE formed the Commercial Engines Projects operation, consolidating the CJ805, CF610, CF700, and the SST programs. Discussions began with various airlines about a new twin-aisle aircraft intermediate in size between the new 747 and the smaller single-aisle aircraft then in use. Both Douglas and Lockheed were studying three-engine aircraft for which a GE engine derived from the TF39 would be suitable. This led to the GE CF6 engine program, led by Brian Rowe (Fig 49). GE eventually dropped support for the Lockheed aircraft (which became the L-1011) and focused on the Douglas program that led to the DC-10-10 (EIS 1971) and the GE CF6-6 engine. This landmark engine enabled GE to re-enter the commercial engine marketplace. The CF6-6 architecture was similar to the TF39 except for the fan, which in the TF39 was a unique “1.5-stage” design. In the CF6-6 the fan is a now conventional single-stage fan with a single booster stage incorporated in the core stream. The CF6-6 produces 40000 lb thrust, has a 5.8:1 BPR and 25:1 EPR (Fig. 50).

Figure 47

Lockheed C-5 Galaxy

Figure 48

TF39 High-Bypass Turbofan

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Growth engines of the CF6-6 were produced with larger fans, added booster and low-pressure turbine stages, improved aerodynamics and materials, and increased temperatures, pressures, and airflow rates. The growth versions include the CF6-50 (46K lb thrust), the CF6-80A (50K lb), the CF6-80C (63.5K lb), and the CF6-80E (72K lb). Applications for these engines include the Boeing 747 and 767, the Airbus A300, A310, and A330, the Douglas DC-10 and MD-11 and the re-engining of the Lockheed C-5. At the time this paper is being written the CF6-80C2 and CF6-80E are still in production. More than 6700 CF6 engines have been delivered to commercial and military customers worldwide.

The success of the CF6 engine program has been followed by other successful large commercial turbofan engine developments. In 1990 the GE90 program was launched. This all-new centerline high-bypass turbofan is the largest jet engine in the world today boasting 115000 lb thrust. It is characterized by its unique composite fan blades (Fig. 51). The GE90 powers the Boeing 777 twin-aisle twin-engine long-range airliner. In 2003 GE launched the GEnx engine for the all-new Boeing 787 “Dreamliner”, again featuring a composite fan and also introducing counter-rotating spools. Each successive new engine has introduced new technologies for better economy, reliability and lower emissions and noise. All of these engines trace their successful lineage back to the venerable CF6 and its role in the success of GE in the commercial marketplace.

Small Turbofan Engines In 1967 the Small Engine Department in Lynn was awarded a U.S. Navy contract for a 9000-lb thrust class

engine for a carrier-based antisubmarine and patrol aircraft that was to become the Lockheed S-3 Viking (Fig. 52). The concept that the GE proposal was based upon was a 6:1 bypass ratio turbofan designed around a modified T64 core. The result was the TF34 turbofan (Fig. 53). The FETT ran in Apr 1969 and the first flight on the S-3 was in Jan 1972. The U.S. Air Force also required a small turbofan engine for a new attack aircraft program that became the Fairchild Republic A-10 (Fig. 54). The first flight of the A-10 was in May 1972. GE eventually produced over 2000 TF34 engines.

The TF34 later found a commercial application in business and small commuter jets in the late 1970’s and into the 1980’s. This commercial version of the TF64 was designated the CF34. In 1988, Canadair launched a 50-passenger regional-let program and selected a growth CF34 to power the plane. In the years since, the regional jet aircraft has become extremely popular worldwide, with many of the new aircraft powered by CF34 engine models. The thrust level has grown from 9000 lb up to 20000 lb on the latest model the CF34-10. Over 4000 CF34 engines

Figure 49

Brian H. Rowe

Figure 50

CF6-6 Figure 51

GE90-115B

Figure 52

Lockheed S-3A Viking

Figure 53

Cutaway of TF34 Turbofan

Figure 54 Fairchild Republic A-10 Warthog

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are in service at the time of this writing and approximately 400 more enter service each year. The latest model will power China’s new regional jet aircraft, the ARJ-21.

Afterburning Turbofans In 1963 GE proposed a two-spool front-fan afterburning engine, designated the MF295, for the DoD TFX

competition, later to become the F-111 aircraft. GE did not win the competition, but gained invaluable design experience. In 1969, in another important competition for the DoD AMSA (Advanced Manned Strategic Aircraft for the F-15) GE again proposed an advanced afterburning turbofan, and again did not win the competition. In Jun 1970, however, the long-awaited breakthrough occurred when GE was selected to develop and produce the AMSA engines for the North American Rockwell 4-engine B-1 bomber (Fig. 55). This engine, the F101 (Fig. 56), was developed around a highly advanced core with a 9-stage compressor, annular combustor, and a highly loaded single-stage turbine. The low-pressure spool featured a two-stage fan with a bypass ratio of 2.2 and three-stage low-pressure turbine. The engine produces approximately 30000 lb thrust. A total of 100 operational B-1 aircraft were eventually produced, however, there was a 4-year delay from 1977 until 1981 when President Jimmy Carter halted the program, to be reinstated by President Ronald Reagan.

The F101 program was extremely successful on its own, both for GE and for the USAF. Approximately 470 F101 engines were produced. What is even more significant is how the successful core of the F101 was leveraged in many GE engine programs that followed. GE immediately promoted a smaller “derivative fighter engine” (F101 DFE) which led to the F110 engine family that now power many of the Lockheed F-16 and McDonnell F-15 fighters, and the re-engined Grumman F-14 fleet. The non-afterburning F118 powers the Northrop B-2 and the re-engined Lockheed U-2 fleet. The most successful, and in many ways most amazing, application of the F101 core was a commercial application, and that story is related in a later section of this paper.

The GE Small Engine Department in Lynn was awarded a contract from the U.S. Navy in 1975 for a smaller afterburning turbofan to power the McDonnell-Douglas F-18 Hornet aircraft (Fig. 58). The engine design and development had already been ongoing since the late 1970’s and involved the GE15 demonstrator engine. The GE prototype engine was designated the J101 and eventually became the F404 turbofan (Fig. 59) producing 16000 lb thrust. The F404 is a relatively low bypass ratio (0.34) design and has been referred to as a “leaky turbojet”. The first flight on the F-18 Hornet was Nov 1978 and EIS was in 1983. A non-afterburning version of the F404 was also developed and powers a number of aircraft including the Lockheed F-117 Nighthawk (Fig. 60) stealth aircraft (EIS 1983). In 1988 an upgraded version of the F404 went into production, designated the F414, for the U.S. Navy FA-18 E/F Super Hornet program (first flight 1995, EIS 1999). The F414 engine system (Fig. 61) is one of the most advanced in current production, producing 22000 lb thrust.

The CFM56 The CFM56 is the most-produced aircraft engine on the market today. The story of how this program started is

quite unusual, and in today’s business environment the program probably would have never been launched. The first generation of short and medium-range commercial jet airliners, with capacities of 100 to 150

passengers, included the Boeing 727 and Douglas DC-9 and later the Boeing 737. All of these aircraft were powered by the Pratt Whitney JT8D low-bypass turbofan. In 1968, GE began studying a new higher-bypass turbofan in the 20-25K thrust range with considerably better performance than the JT8D. This study engine, called the GE13, would have a new core featuring an advanced nine or ten-stage compressor and a highly-loaded, single-stage turbine. A similar core was being studied for a new military turbofan engine that eventually became the F101 for the B-1 bomber. At about the same time, the French engine manufacturer SNECMA had begun design studies for an engine of similar size for a proposed 150-passenger European transport aircraft. This engine program had

Figure 55

Rockwell B-1 Lancer

Figure 56

F101 Afterburning Turbofan

Figure 57

F110 Cross Section

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been designated the M56. The SNECMA president, René Revaud, had been encouraged by the French government to seek assistance on the program from an established engine manufacturer. At the Paris Air show in June 1971, Revaud met with Gerhard Neumann and preliminary discussions began around the idea of a partnership between GE and SNECMA to develop the new engine. Over a period of several months the details of this unique partnership were worked out. The arrangement was a 50-50 joint venture, with each party sharing half of the engine production and half of the revenues. GE supplied the advanced engine core engine from the F101, and SNECMA supplied the fan, low-pressure turbine, and the accessory gearboxes. Numerous other issues such as the systems, sales and marketing, and project leadership, as well as the necessary government approvals, also were worked out. The new engine program was designated the CFM56 (Fig. 62), combining GE’s “CF” (for commercial fan) designation with SNECMA’s “M56”. Detailed design and development efforts proceeded in earnest on both sides of the Atlantic, culminating in the FETT in 1974.

Initial testing of the CFM56 was extremely successful and engine performance met all expectations. There was one very major problem, however … there were no customers for the new engine. Flight tests of the CFM56 continued, however, using different test bed aircraft in the US and in France. Some interest had materialized in the CFM56 as a replacement for the outdated powerplants on the 4-engine Douglas DC-8 and the Boeing 707 and KC-135. The initial order for the CFM56, which was finally announced in 1979, was a re-engine order for DC-8 aircraft (Fig. 63) operated by United, Delta, and Flying Tiger Airlines. United Parcel Service also became a customer for their DC-8 fleet. These orders got the CFM56 into small-scale production. The French Air Force then launched a program to re-engine their KC-135 fleet. The success of this program led the US Air Force to then consider a re-engine program for their considerable KC-135 fleet. After very competitive negotiations, the USAF chose the GE engine. This win put the CFM56 program into the black with over 2000 engines in the order book.

In 1981 Boeing launched the design of an updated model of the successful 737 twin-engine airframe (Fig. 64) designed around the CFM56 engines. From the outset the plane was a hot seller and has remained so to this day. Over the years the airframe and engines have been significantly improved in response to customer needs and technology introduction. At the time this paper is being presented, approximately 17,000 CFM56 engines have been put into service by over 400 customers, and the number increases by about 100 engines every month. Every 3 seconds an aircraft powered by CFM56 engines takes off somewhere in the world. The CFM56 has been the most successful commercial aircraft engine program in history.

Summary As pointed out at the beginning of this paper, the full story of aircraft jet engines at the GE Company would

require (and has been the subject of) a complete book, or several books. It was not the intent of this paper to do that. This paper attempts to summarize, in a concise and easily readable format, how the General Electric Company became a designer and producer of aircraft jet engines. It also attempts to trace the events that led to GE becoming a successful producer of jet engines for both military and commercial applications in a wide range of application requirements. There are numerous other programs and products that are not mentioned. For example, in the 1950’s GE carried out a major program aimed at the design and development of a nuclear-powered jet propulsion system for an intercontinental bomber application. Also no mention has been made of the field of aeroderivative gas turbine engines, for electric power generation and marine propulsion, of which GE is a major producer. Mention is made of

Figure 59

F404 Turbofan

Figure 58

McDonnell-Douglas F-18 Hornet

Figure 60 Lockheed F-117 Nighthawk

Figure 61

F414 Turbofan

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a number of the key historical figures that were involved in this history, but dozens of others deserving of recognition have not been introduced. The reader is encouraged to consult the references below to learn more about these other programs and people. In addition, there is a wealth of information available on the internet, including at the GE Company websites.

GE makes a lot more than just light bulbs and appliances!

References 1. Eight Decades of Progress: A Heritage of Aircraft Turbine Technology, General Electric Co., (1990). 2. Garvin, Robert V., Starting Something Big: The Commercial Emergence of GE Aircraft Engines, AIAA (1999). 3. Levenson, Eugenia, “The World's Most Admired Companies”, Fortune Magazine, March 2, 2007. 4. St. Peter, James, The History of Aircraft Gas Turbine Engine Development in the United States: A Tradition of Excellence,

ASME (2000).

Figure 62

CFM56 Turbofan

Figure 63

Douglas DC-8 Series 70 Re-engined with CFM56

Figure 64

Boeing 737-300 with CFM56