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Aviation History
1989
1989 - 0065.PDF
P&W/Allison propfan flight due by Kieran Daly Flight-testing of the Pratt & Whitney/Allison 578-DX propfan is due to start this month on the McDonnell Douglas MD-80 ultra-high- bypass demonstrator aircraft. The engine has been installed on the port side of the aircraft formerly used to test the General Electric GE36 unducted fan. A standard JT- 8D turbofan is retained on the starboard side. Douglas says that the only significant modification was to the port pylon, to control vibration in the rear fuselage. Ground runs began last week, and flight testing will last until the spring. PWA completed 200hr of ground tests before the engine was installed in the aircraft. The project suffered delays following problems with the pitch change mechanism, but has since kept to schedule. Difference The key difference between the GE36 and the 578-DX is that the latter incorporates a gearbox linking the turbine to the propulsor blades. The gearbox allows the propulsor to rotate at low speed to achieves noise reduction, while the turbine turns at its much higher opti mum speed. In the GE36 the propulsor blades are attached directly to the outside of the two contra-rotating turbines, which rotate at exceptionally low spfeed for aviation units. General Electric says it is pleased with the progress of its engine, while stressing that "the bottom line is that we are not going to launch an engine with out an aircraft to sell it on". McDonnell Douglas is actively marketing its proposed family of mid-range MD-90 airliners, but has not yet secured an order. It does not express any preference for either engine, but points out that it is now able to discuss GE36 performance figures with potential customers following the first phase of air tests. It also says the "quality" of a possible launch order is as important as the quantity. An . order from a. major US or European carrier would be particularly likely to trigger production, even if it were rela tively small. General Electric is still discussing other applica tions with Airbus and Boeing, but the MD-90 range remains its major hope. During 1989 General Elec- The Pratt & Whitney/Allison geared propfan is readied at Edwards Air Force base for its first flight this month trie will continue to develop the GE36, with flight testing of a more advanced version due next year. A GE36 core will be tested in the first quarter of 1989, and a full gas generator by the end of the year. A new pitch change mechanism will also be developed. The company says there is still no definite plan to fly an aircraft with two GE36s installed, and it will not attempt to gain Certification without a launch order. Propfan looks to China Allison Gas Turbine and the China National Aero- Technology Import and Export Corporation (Catic) are to study the possible joint development of a propfan engine for the MPC 75 airliner being worked on by Catic and MBB of Germany. MBB already had an agree ment with Allison to collaborate on the engine. The proposed unit is a derivative of the T406 under development for the US Navy's tilt-rotor V-22 Osprey, which has still to fly. The MPC 75 is scheduled to fly in the middle of 1994. Belgians clear Redigo The Valmet Redigo prototype's crash at Kleine-Brqgel in Belgium last year was not caused by technical failure, the final accident report says. ••• The Belgian Civil Aviation Authority's report sees |*no circumstances which wd.uld lead to a conclusion that aircraft structure or any of the aircraft systems had failed during the flight, or that the operation of the control system had been hampered. Nor did the investigations reveal any fault or damage which would have been present prior to the flight." The report concludes: "the probable cause of the accident was a spin executed during a display with a prototype starting too low in view of the safety margins. Consequently, the recovery took place too late and the crash was inevitable." FLIGHT INTERNATIONAL, 14 January 1989 7
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