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Aviation History
1993
1993 - 1792.PDF
General Electric's flight-test op eration (FTO) has grown with the fortunes of the company's commercial jet-engine busi ness. Now, as engine makers face the hardest financial conditions of modern times, the pressure to test and certificate at peak efficiency is higher than ever. To meet these demands, GE's FTO is gearing up for future multi-role testing with a Boeing 747 testbed at Mojave, not far from Edwards AFB, California, where it emerged originally as a test operation for military-jet developments. The company's Flight Test Center began its association with commercial engines in the late 1950s with GE's CJ805-3 turbojet, a civil version of the J79. The engine for use on the Convair 880 was flight-tested aboard a modified Douglas RB-66 at Edwards. Establishing a trend in 1961, the unit obtained a Sud-Aviation SE.210 Caravelle, which was used as a testbed for the CJ805-23 turbofan, an aft- fan version of the CJ805-3. This engine powered the Convair 990. Flight-tests of the CF6, a civil version of the TF39 turbofan used on the Lockheed C-5, were conducted by the FTO at Edwards using a Boeing B-52 testbed. The FTO then moved to the less-restrictive Mojave in 1971. Today, a Boeing 747-100 testbed sits on the FTO ramp at Mojave, California, dwarf ing its veteran predecessor, a 707-321. The 747, which arrived in January 1993, represented an inevitable leap for the hard-working FTO. The sheer size of GE's latest turbofan, the 3.12m diameter GE90, meant that only the world's biggest airliner was suitable for the job of testing the engine safely. Although the 747 is larger and more costly than the 707 and the Airbus A300B4 which the FTO operated for some time as a CF6 testbed, the overall aim is to use the Boeing as a multi-role test aircraft. This will produce savings, as CF6, CFM56 and GE90 testing will be possible on the same aircraft, allowing the 707 to be retired. "That's the plan, anyway," says FTO programmes manager, Robert Chappell. "We're taking a look at what it takes to make the 747 a universal testbed, and if it gets rolling, the 707 could go away." The stalwart 707 is not finished with yet, however. A busy test series is ahead of it, lasting until at least the end of 1993. The aircraft has been dedicated to the testing of CFM International CFM56- series engines and will probably end its FTO life being used to flight-test the GE/Snecma joint venture's new low- emissions double-annular combustor in a -5B at the end of the year. THE 707 TESTBED "The 707's been great, but it's hard to maintain," says FTO test pilot Carroll Beeler. "As far as we know, it's just about one of the only ones still flying with Pratt & Whitney JT4Ds, apart from some that the Israeli air force have." The 707, which was first used by the FTO for CFM56 testing in 1982, was joined by the A300 in early 1984. The Airbus was returned to Toulouse, France, in the third quarter of 1992 after flight- testing of the CF6-80E1. The aircraft is now being used for various research flights in France, including laminar-flow tests and zero-g runs. With work accelerating towards the first flight of the GE90, the 747 is the focus of activity at the FTO. "Since the aircraft arrived from Lucas [formerly Tra- cor, in Santa Barbara], we've put in a data system and we're extending the wiring out to the No2 [port inboard] engine position. The No2 engine has been removed and we've put in an interface panel for instru mentation and all the parameters that will be measured," says Chappell. "The data system is aboard and being checked out," he adds. The adaptor and strut for the GE90 were fitted to the existing wing-pylon position on 8 July. "The engine is due out here on 1 August from Peebles [GE's test site in Ohio], and will be all checked out before it arrives here so, as far as instrumentation goes, we should be able to mount it the next day." The 747's new data-collection system forms a critical element of the FTO's future plans. According to Beeler: "We've been learning as we've been testing over the past ten years and we've tried to take all that accumulated knowledge and apply it to the next aircraft." Along with the need for an improved data system, the FTO's experience pointed towards selecting the 747, not only be cause it was the only aircraft suitable for testing the GE90, but because it could be used to flight-test current and future engines across the power range. "We needed a bigger and more capable aircraft. Two engines is very limiting, but, with a four-engined aircraft, you can take it where you want it, and as hard as it goes," says Beeler. The size of the 747 also helped to accommodate what promises to be an extensive array of flight-test equipment. Hoping that the change from the narrow body of the 707 to the longer, wider 747 would give them more room, some test engineers have been a little surprised. Underlining the apocryphal tenet of Park inson's law, namely that "equipment ex pands to fill the space available", the 747's main deck will house up to 87 racks of monitoring and recording systems. Cabi nets will be arranged in rows of six on one side and rows of four on the other. "From business class backwards is all instrumentation," explains Chappell, who adds that the deck weight poses no worries, as the ex-Pan American World Airways aircraft had undergone the civil- reserve air-fleet strengthening programme. "The data system on the 707 was a kind of hand-built conglomeration. The 747 has an advanced system which is the same as the one being used back at Peebles. It takes up between 2,500 to 2,700 parame ters — that's four times or more greater than the 707. We were limited on the 707 to the 600-ish range," he says. Changes to the data system also pro duce a major operational improvement for the FTO. "These range from performance to operability. There are phase changes with the existing system which involve having to constantly re-configure the air craft and, with this, we won't have to. It kind of reduces test time and makes it like the GE90 Peebles test cell," says Chappell. "The first engine will go through Pee bles with a big preparation area. They will build everything up there and hook it up and check instrumentation right there. Then they raise it up into the overhead thrust rig. By doing it that way, it's been co-ordinated with the aircraft, so there are no changes in the aircraft wiring. We just have to plug it in," he says. Ground runs are scheduled for the last week in August and the long-awaited first flight is due on 7 September. "The flight- test programme will go from September into the middle of October," says Chap pell. In October, the GE90 will be fitted with a host of Boeing 777-specific engine build-up units, such as bleed systems and accessories. "That will probably take up to three or four weeks," he adds. FLIGHT TESTING Flight-testing is then expected to resume in November and run through to the end of December. "That will complete the engine envelope — performance, op erability and systems," says Chappell. Following basic clearance, GE90s will be shipped to Boeing in Seattle for instal lation on the first GE-powered 777. Certi fication of the engine is due in November 1994 and the GE90/777 engine airframe certificate is expected the following Au gust. The first engines are scheduled to enter service on a British Airways "A market" 777 in September 1995. Initial engines for the lighter 777s will be de-rated from the certificated thrust FLIGHT INTERNATIONAL 21 - 27 July, 1993 27
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