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50-719: A commercial version, designated the CJ805 , powered the Convair 880 , while an aft-turbofan derivative, the CJ805-23, powered the Convair 990 airliners and a single Sud Aviation Caravelle intended to demonstrate to the U.S. market the benefits of a bypass engine over the existing Rolls-Royce Avon turbojet. In 1959 the gas generator of the J79 was developed as a stationary 10MW-class (13,000 bhp) free-turbine turboshaft engine for naval power, power generation, and industrial use, called

100-412: A compressor with a wide speed-range of operation". An experimental 12-stage compressor was built with the inlet guide vanes and first four rows of stator blades adjustable to lower the air incidence angles while running at low speed. It was very effective in overcoming the stall and surge. However, a simpler mechanical-design solution (variable inlet guide vanes and bleed) had already been shown to work with

150-587: A disadvantage in combat aircraft making them vulnerable to visual detection. Later models were redesigned to be "smokeless". The turboshaft counterpart to the J79 is the General Electric LM1500, used for land and marine applications. Many J79 derived engines have found uses as gas turbine power generators in remote locations, in applications such as powering pipelines. The J79 has two commercial derivatives: CJ805 -3 (a non-afterburning engine, fitted with thrust reverser and sound suppressor), and

200-511: A disc, made up the aft rotor assembly. The efflux from the turbojet expanded through the (inner) turbine annulus, thus providing power directly to the fan blades located in the outer annulus. A full-length cowl, an annular exhaust system and a bucket thrust-reverser were fitted for the Convair 990. The unique feature of the CJ805-23 was the transonic single stage fan. NACA had done significant research on multistage transonic compressors during

250-577: A new supersonic bomber, which became the Convair B-58 Hustler . The two other engines offered by GE, an advanced version of the existing J73 and a much larger design, known as the J77, were both cancelled. The first prototype of the production version, XJ-79, ran on 8 June 1954. The first flight of the engine was on 20 May 1955 with the engine installed in a General Electric J47 -powered North American B-45C Tornado ( serial 48-009 ) . In flight

300-557: A new version with a relatively short fan cowl and thrust reverser, compared to the full-length cowling on the 990. Rolls-Royce quickly built and tested an aft-fan demonstrator Avon to compete with the greater thrust and lower specific fuel consumption of the CJ805-23. In the end, the Caravelle was instead re-engined with the P&;W JT8D turbofan. The CJ805 program was not a commercial success, and GE lost approximately $ 80 million on

350-537: A powerful, lightweight design 2,000 lb lighter than its 2-shaft competitor for the B-58, the J57 engine, and GE began considering it as the basis for a high-power engine for commercial use. In 1952, Chapman Walker's design team at GE built a one-off prototype of a jet engine designed specifically for transatlantic airliners. It used a single-stage fan powered by the same turbine shaft as the main engine compressor, as opposed to

400-501: A serious issue. There was already a lawsuit, by residents around Newark airport, concerning the noise from existing propeller-driven aircraft such as the Lockheed Super Constellation , Boeing Stratocruiser and Douglas DC-7 C. One way to reduce this problem is to mix cold air into the jet exhaust, which was accomplished on early engines with the addition of scalloped nozzles. This solution was also adopted for

450-454: A similar pressure ratio for their JT-3D turbofan. Although not an overhung design, the CJ805-23 transonic fan did not require any inlet guide vanes. There was, however, a series of structural vanes to help support the fan casing. With additional changes, fuselage stretches, and the addition of anti-shock bodies , the new airliner emerged as the Convair 990. However, by this time the project had suffered several delays, allowing new versions of

500-503: Is a jet engine which was developed by General Electric Aircraft Engines in the late 1950s. It was a civilian version of the J79 and differed only in detail. It was developed in two versions. The basic CJ805-3 was a turbojet and powered the Convair 880 airliner, and the CJ805-23 (military designation TF35 ) a turbofan derivative which powered the Convair 990 Coronado variant of

550-616: Is at a high compressor speed for take-off or cruise. If designed for high efficiency at high speeds it was very inefficient and prone to stall at low speeds. In 1944 the National Advisory Committee for Aeronautics had tested a theory for "Extending the useful operating range of axial-flow compressors by use of adjustable stator blades" by running an eight-stage axial compressor with pressure ratio 3.42:1 and adjustable blade angles. Considerable improvement in efficiencies were obtained at compressor speeds appreciably below

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600-417: Is known as "off-design" and required the invention of special devices to make the compressor work. The compressor worked well near its maximum speed, known as "design", with a fixed area convergence from entry to exit to go with the design values of compression/density and with fixed blade angles set to give low pressure losses. At low speeds the much lower compression didn't squeeze the air enough to get through

650-407: Is relatively unimportant. Further increases in pressure ratio, demanded by government procurement agencies and commercial airlines for long-range aircraft, caused a bigger mismatch of flow areas/density changes and blade angles. Two approaches were followed: slowing the blade speeds at the front of the compressor by splitting it into two separately rotating parts (spools) or making stators variable on

700-719: The CJ805 -23 (with a free-wheeling aft fan and thrust reverser) fitted to the Convair CV-880 and the Convair CV-990 respectively. J79 engines may be started using compressed air directly on the engine turbine blades or by using a turbine starter attached to the accessory gearbox. The gas used in this starter is either compressed air or from a solid propellant cartridge. Data from Jane's All The World's Aircraft, J79 - Turbine Engines: A Closer Look Related development Comparable engines Related lists General Electric CJ805 The General Electric CJ805

750-657: The F-111 and F-14 , and newer generation turbofans with the Pratt & Whitney F100 used in the F-15 Eagle which give better cruise fuel efficiency by-passing air around the core of the engine. For their part in designing the J79, Gerhard Neumann and Neil Burgess of General Electric Aircraft Engines were jointly awarded the Collier Trophy in 1958, also sharing the honor with Clarence Johnson (Lockheed F-104) and

800-519: The LM1500 . Its first application was in the research hydrofoil USS  Plainview . By the late 1940s, jet engine design had progressed to the point where further progress was limited by the performance of its compressor, in particular the pressure ratio of the compressor had to be increased to reduce the engine fuel consumption. However, the useful operating range of the compressor was limited at that time and centered around its design condition which

850-482: The Pratt & Whitney designs that were using a separate power shaft to run the fan. The GE design proved to be difficult to start and operate and was not developed further. In 1955 Jack Parker took over GE's Aircraft Gas Turbine division. He hired Dixon Speas to begin interviewing executives at airlines to try to get a sense of the future market. Parker asked Speas to interview not the CEOs, but executives that might be

900-447: The 1950s. Using this data, GE decided to design and test a high-pressure ratio single stage transonic fan. Much to their amazement the unit more than met the design target, including that of high efficiency. A modified version of this research unit was subsequently incorporated into the CJ805-23 aft fan. With no experience of transonic fan design and little time available, Pratt & Whitney had to resort to using 2 fan stages to produce

950-402: The 880. Turbojet engines consist of a compressor at the front, a burner area, and then a turbine that powers the compressor. In order to reach worthwhile compression ratios , compressors consist of multiple "stages", each further compressing the air leaving the previous one. One common problem with early jet engines was the phenomenon of "surging" or compressor stall . Stalls could occur when

1000-498: The Aircraft Gas Turbine Division lead, C.W. 'Jim' LaPierre, formed two teams to do design studies for an engine that could run for extended periods at Mach 2.0 while still giving good fuel economy while cruising at Mach 0.9. Neumann led a team using a variable stator configuration, while Chapman Walker led a parallel effort using two-spools. After a years study the engine with variable stators was chosen as it

1050-512: The CEO by the time GE was ready to enter the civilian jet engine market. Parker, Speas and Neil Burgess, who ran the J79 program, spent a month meeting with American Airlines , Delta , United , KLM , Swissair and SAS . The meetings demonstrated that those airlines that were flying propeller aircraft across the Atlantic were all looking to replace them with jets. Around the same time, Convair

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1100-587: The CJ805. Several airlines asked Convair for a larger version of the 880 with potential transatlantic range. Such a design would be larger to hold more seating, as well as having to carry more fuel. To power it, a more powerful engine would be needed. By this time, the Rolls-Royce Conway was entering service, and the Pratt & Whitney JT3D was following close behind. These designs both had twin-spool compressors, as opposed to using variable stators, and

1150-528: The DC-8 and 707 to lock up major sales. In the end, Convair sold only 102 880s and 990s in total, losing $ 600 million on the program. There was only one other customer for the 805-23. In 1961, Sud Aviation approached GE to pitch them on the idea of adapting the Rolls-Royce Avon powered Caravelle to the 805-23, producing a flying technology showcase for both companies. For this role they introduced

1200-500: The J79 was lowered from the bomb bay into the airstream for testing. The first flight after the 50-hour qualification test, required for a new engine that is the sole source of thrust for a flying testbed, was on 8 December 1955, powering the second pre-production Douglas F4D Skyray , with the J79 in place of its original Westinghouse J40 engine as part of the General Electric development and qualification program. The YF-104

1250-643: The US Air Force (Flight Records). The compressor blades and vanes are made of 403 stainless steel , except for the -3B and -7A variants, which have A286 vanes at stages 7 through 17. The compressor rotor is made of Lapelloy, B5F5 and titanium. The J79 makes a particular howling sound at certain throttle settings. This strange feature led to the NASA operated F-104B Starfighter, N819NA , being named Howling Howland . Early engines also produced noticeable quantities of smoke, especially at mid-throttle/cruise settings,

1300-608: The US, and under license in Belgium, Canada, Germany, Israel, Italy, and Japan. A downgraded version of the General Dynamics F-16 Fighting Falcon with a J79 was proposed as a low-cost fighter for export, and though a prototype aircraft was flown, it found no customers. The J79 was replaced by the late 1960s in new fighter designs by afterburning turbofans such as the Pratt & Whitney TF30 used in

1350-705: The United States. It was used in many types of aircraft, and more than 30,000 were manufactured before production ceased in 1956. It saw continued service in the US military until 1978. Packard built 3,025 of the engines under license. The J47's greatest advantage, as advertised, was its array of features which were unavailable and unprecedented in any other engine. It was advertised as an 'all-weather engine' due to its anti-icing systems which allowed it to perform at high altitudes and extreme temperatures where other aircraft's performance suffered. Its development began without an explicit need for it, although this design

1400-420: The addition of a completely separate fan system at the rear of the engine, powered by a new turbine stage. The system was essentially a bolt-on extension to the existing design and had almost no effect on the operation of the original engine. Each turbine blade was an integral part of a "blucket", the outboard section of which was a fan rotor blade. Running freely on a stub shaft, a series of buckets, mounted on

1450-421: The approaching airflow was not in-line with the aircraft inlet to the compressor or when the throttle was advanced too quickly. When engines had to be designed with pressure ratios greater than about 5, to meet demands for reduced fuel consumption, a new stalling phenomenon came to light, rotating stall. It occurred at low compressor speeds and caused blades in the first stage to break. This troublesome speed area

1500-437: The best way of designing the compressor for the high required pressure ratio of 12:1. This pressure ratio was needed to achieve the supersonic performance, subsonic cruise performance and low weight necessary for future supersonic aircraft. In 1951, a General Electric team led by Gerhard Neumann , at that time in charge of engine development testing, was given funding to build a test compressor with variable stators. In addition,

1550-442: The competing Douglas DC-8 and Boeing 707 was a higher cruise speed. This demanded more engine power from a lighter design, which naturally led to a design like the J79. To gain experience with the engine in a civil setting, GE equipped a Douglas RB-66 with the new engine and flew simulated civil aviation routes out of Edwards Air Force Base . As development progressed, the 707 began to enter service, and noise complaints became

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1600-453: The design speed. Departures of velocity from the design condition are most noticeable in the first stages at low rpm and become more so as the design pressure ratio is increased leading to blade stall and compressor surging as happened with the Rolls-Royce Avon compressor, with design pressure ratio of 6.3:1 in 1949. In 1947 Geoff Wilde , a Rolls-Royce compressor designer, had applied for a patent "Axial flow compressor regulation" "to provide

1650-457: The engine RPM increases towards operational speeds. Another solution was the use of variable inlet vanes. The angle of incidence of the vanes at the front of the engine is changed to partially block the inlet area, which reduces the compression, and also angle the air onto the compressor blades to prevent stalling. This has the advantage of being more efficient than allowing valuable compressed air to escape, although fuel consumption at low speeds

1700-572: The engine include: In the 1950s, interest in the development of nuclear-powered aircraft led GE to experiment with two nuclear-powered gas turbine designs, one based on the J47, and another new and much larger engine called the X211 . The design based on the J47 became the X39 program. This system consisted of two modified J47 engines which, instead of combusting jet fuel, received their heated, compressed air from

1750-602: The engine led to it becoming the most produced jet engine in aviation history, and established GE Aviation as a worldwide leader in jet propulsion. Overhaul life for the J47 ranged from 15 hours (in 1948) to a theoretical 1,200 hours (625 achievable in practice) in 1956. For example, the J47-GE-23 was rated to run 225 hours time between overhauls . As installed on the F-86F, it experienced one in-flight shutdown every 33,000 hours in 1955 and 1956. Ground-based vehicles that used

1800-636: The engine was first tested. The engine featured an electronically controlled afterburner , a system that dumped additional fuel into the combustor pipe 'behind' the engine, reheating the exhaust and producing significantly more thrust, although with greatly reduced efficiency and high fuel burn rates. The engine production process in the Lockland facility (renamed to the Evendale facility) utilized vertical engine assembly to ensure compressor rotor balance and stability. The technological jump provided by

1850-622: The engine's problems. GE quickly gained a reputation for standing behind their products that endures to this day. The work on the 805 also had several spin-off products. Among them was another aft-fan design, the General Electric CF700 used in the Dassault Falcon 20 business jet, which was developed from the General Electric J85 in the same way as the J79 was adapted to the 805. Their fan technology

1900-464: The first few stages as well as the inlet vanes. A disadvantage is significant mechanical complexity as each stator blade has to be independently rotated to the desired angles. Two spools need more bearings and turned out to be heavier. Bleed valves, two or three spools and variable stators are all used together on modern engines to cope with rotating stall during starts and at low speeds and to allow surge-free fast accelerations. Rolls-Royce considered

1950-438: The lower speed of the front, low-pressure, spool made it easy to power a fan. The problems RR and P&W had addressed with the two-spool system had been solved on the J79 with the variable stators, so in relative terms, the single compressor rotational speed was much faster than the low-pressure stage of these other engines. This meant it was not suitable for direct connection to a fan stage. Instead, GE solved this problem with

2000-423: The now too-small exit. The velocity triangle combined the now too-slow entry air with the blade speed and gave a stalling angle. One common solution used on early engines, and widely used today, was to give the air extra escape holes to speed up the entry air, i.e. the use of "bleed air" which is allowed to escape from openings near the middle of the compressor stages and vented overboard. The bleed valves close as

2050-413: The program with only a few hundred engines produced in total. In service, the design proved fragile, but these problems led to the programs ultimate success for the company. During the time they were talking to airline CEOs, in 1956 the company hired the former head of American Airlines' maintenance department, John Montgomery, to run the production lines. Montgomery gathered comments from the industry on

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2100-429: The required design pressure ratio so variable stators were not used in a Rolls-Royce engine until the 1980s ( IAE V2500 ). By 1950 General Electric was focussing on supersonic engines with variable stators as a result of design studies which compared them with dual-rotor types. Based on their past experience at that time, and estimation of the development effort required to prove new technologies, variable stators promised

2150-499: The state of the engine market, and found that many were complaining about the unreliability of the large piston engines then being used, notably the Wright R-3350 . Wright management refused to put more money into the program to improve the engine, leading to a serious backlash from the customers. Montgomery hired Walter Van Duyan away from Wright to set up GE's service department, and they provided excellent service in spite of

2200-564: The variable stator idea in the 1940s, but abandoned it until using it in the 1980s on the V2500 engine. They began development of two-spool designs, a concept that was also selected by Pratt & Whitney . The variable stator path was only selected by GE after a year-long design study competition comparing two spools and several stages of variable stators with objectives of efficient performance at cruise Mach 0.9 and at Mach 2, increased thrust, reduced fuel consumption and weight. The J79 emerged as

2250-535: Was also used in the XV-5 Vertifan . Data from FAA Type Certificate Data Sheet, E-306 Data from [1] Related development Related lists General Electric J47 The General Electric J47 turbojet (GE company designation TG-190) was developed by General Electric from its earlier J35 . It first flew in May 1948. The J47 was the first axial-flow turbojet approved for commercial use in

2300-471: Was canvassing US carriers and found demand for a smaller jet aircraft for medium-range domestic routes. They began development of what would become the 880, and approached Burgess to see if GE could develop a version of the J79 for this role. Burgess responded by quickly sketching a version of the J79 with the afterburner removed and replaced by a thrust reverser , giving them an estimated unit price of $ 125,000 per engine. The 880's primary sales feature over

2350-492: Was described by Flight magazine in 1948 as the most widely used American-conceived turbojet. The turbojet featured a revolutionary anti-icing system where hollow frame struts allowed heated airflow to pass through from the compressor , allowing fighter jets equipped with the engine to function at high altitudes, and in cold conditions such as the top of Mount Washington in New Hampshire's White Mountains , where

2400-625: Was lighter, simpler and had a smaller diameter. A demonstrator engine with variable stators, the GOL-1590, predecessor to the J79 was built. At the same time a new engine, the X-24A, was designed for a supersonic aircraft and selected by the Air Force. Development of the new engine was supported by running the GOL-1590 demonstrator engine. GE won the Air Force contract for a new engine with approximately 14,000 pounds thrust, with afterburning, to power

2450-592: Was quickly purchased by the military for its many potential benefits. In 1978, J47s were formally withdrawn from active military duty when the Air National Guard retired the jet-boosted KC-97Js. Despite this, these engines are still extensively utilized in F-86 Sabre jets owned by civilians, making them a common sight at air shows. The J47 design used experience from the TG-180/J35 engine which

2500-612: Was the next airplane to fly with the J79 followed by a re-engined Grumman F11F Tiger in a Navy-sponsored program to gain experience with the engine before the first flight of the F4H (F-4). The J79 was used on the F-104 Starfighter, B-58 Hustler, F-4 Phantom II, A-5 Vigilante, IAI Kfir aircraft and the SSM-N-9 Regulus II supersonic cruise missile. It was produced for more than 30 years. Over 17,000 J79s were built in

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