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Aviation History
1993
1993 - 0278.PDF
0.7m aft from its present location above the starboard-engine nacelle. The exhaust will be relocated on the first aircraft "...at the end of April or beginning of May", says Henne. Scott Brandenburg, commer cial sales director for the APU manufac turer, AlliedSignal Auxiliary Power division, says that the new exhaust loca tion will also "...improve the acoustics at the galley-service-door area". Brandenburg says that the APU exhaust change will not have any effect on its own programme, which is on schedule. The company's Garrett GTCP131-9D unit, ca pable of 335kW (450hp), was installed in November 1992 and re-installed at the turn of the year, after being removed to allow final calibration of the IAE engine installation weights. The company is now tackling the prob lem of partially re-designing the APU compressor containment casing after the unit failed during recent engine-compres sor containment quality testing. A "beefed-up" unit will be sent for installa tion in the T2, the second test MD-90, on 17 May and a "conformed" APU is set to be retrofitted to the Tl in mid-April. Despite the emergence of the latter issue, Brandenburg says: "Overall, we're pretty pleased with the programme." Apart from the first flyable unit in the MD-90, one is in AlliedSignal's Arizona test cell and five on the production line. Other changes also include the addition of extra redundant features to the elevator power-control system. This unit, built by Dowty Aerospace Los Angeles (DALA), should ensure good pitch response despite the MD-90's increased pitch inertia. The new twin's pitch inertia is greater because the weight of the aircraft aft of the wing has been increased by 2,700kg as a result of fitting the larger engines and associ ated support structure. The fuselage length also con tributes to the increased iner tia, it having been stretched by 1.45m forward of the wing, to balance out the additional weight in the tail. DALA engineer Tom Ver- beek says that the change is "just an increase in redundancy within the mechanical system of the elevator power-control unit", and is "not a big change". It was a late change, however, directed by DAC. DALA is building flight-standard hard ware for installation in the T2 and to be retrofitted in the Tl. DALA, which also produces the hydrau lic emergency cut-off unit and manual- reversion cylinder (which reverts elevator control to manual, using trim tabs on the elevator trailing-edge in the case of dual hydraulic-systems failure) is scheduled to provide the rudder actuator in later aircraft. NEW-TECHNOLOGY ADVANTAGE As a tailor-made product of the 1990s, the twinjet incorporates an avionics system built to handle inputs from global- navigation satellite systems (GNSS). Honeywell Air Transport division MD- 80/90 programme manager Gordy Hand- berg says that many of the avionics systems have been "altered substantially" to take advantage of the newest develop ments promised for GNSS navigation. "The digital flight-guidance system and flight-management computer [FMC] have been built to take advantage of the GPIRS [global positioning/inertial reference sys tem] . The IRS has built-in capacity to deal with GPS and has software ready to receive GPS inputs." "GPS is a burgeoning field itself and is growing so fast that any airline would want to make provision for it," he adds. "Douglas is pretty clever in that way — laying out avionics in such a way as to avoid cost and problems later on." Honeywell supplies 56 systems for the MD-90, excluding the buyer-furnished op tions of weather radar and traffic-alert and collision-avoidance system. The FMC has auto cutback on the throttles and the MD-90 "...is the first aircraft available with this option", says Handberg. The air-data computer is also developed uniquely for the MD-90, and is more powerful than its predecessors, to cope with the increased digital output of the aircraft's predominantly used 429 databus, as well as the secondary 575 databus. "We're pretty excited about it," says fuselage has been stretched J.45m forward of the Handberg. "The programme's gone re markably well. We are totally set up for production and that's unique. That's a first for us and it's partially because of the derivative nature of the programme and partially because we have done everything right so early." While suppliers are early, DAC appears to be making the second MD-90 late. There is a reason for this, however, as Henne explains: "T2 [the second test aircraft] has always been six to nine months behind Tl, so we've had time to allow incorporation of any changes. Now, it's coming along and the big bones of it are here. The nose is here and the wing is in final join at McDonnell Douglas Canada. The tail has arrived from Tulsa and the fuselage modules are about com plete," says Henne. The T2 is expected to be "on rubber" (standing on its own undercarriage) around mid-March. The aircraft will be fitted with engines in June and will have its first flight in mid-September. Having established new production methods for the MD-90, Henne now faces the challenge of keeping them going until the same manufacturing principles are adopted for the MD-80 line in 1994. "The biggest challenge is keeping everyone working in a concurrent mode — rather than a serial mode. Engineering, fabrica tion, planning and tooling is all in parallel rather than in series." The emergence of the MD-90 comes as DAC approaches a significant crossroads in its history. Having depended for so long on its derivative developments, DAC found itself competing in restricted areas of the mar ketplace. It then attempted, and has so far failed, to break out of the enclave with the MD-12 and Taiwanese investment. Now, with the MD-12 in suspended animation and the search for investors continuing, DAC needs breathing space. The fortunes of the commercial-jet market have plunged in the wake of airline losses and DAC is preparing to cut its workforce to 15,000 as production slows. The MD-90 could provide DAC with breathing space and its marketeers with a much-needed boost. "It will be the best performer in its size and we are the best prepared for the next set of environmental rules," says Henne. While having lost some orders, the MD-90 orderbook has now stabil ised, with 77 firm commit ments. "We're OK, but we'd have loved to have a backlog of 500," says Henne. If all current options, wing commitments and firm or ders are exercised, the MD- 90 production backlog rises to 179. Additionally, some airlines have reserved the right to convert orders for 60 MD-80s into the new twinjet, bringing potential MD-90 sales so far to 239. With a backlog of 283 for the MD-80/90 and the MD-11, as of 31 December, 1992, the MD-90 is an increasingly vital part of DAC's survival strategy for the decade. B FLIGHT INTERNATIONAL 10 - 16 February, 1993 23
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