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Aviation History
1991
1991 - 2108.PDF
NEWS ANALYSIS THE COST OF BROKEN PROMISES Exasperated by months of confusion over P&W-powered MD-11 performance, Singapore Air Lines has cancelled its order for 20 of the aircraft in favour of Airbus A340-300s Singapore Airlines' (SIA's) un precedented decision to can cel its order for up to 20 Pratt & Whitney (P&W)-powered McDonnell Douglas MD-lls (Flight International, 7-19 Au gust) leaves Douglas smarting over what it sees as a major let-down by its partner, and Pratt & Whitney (P&W) facing the potential loss of one of its most important customers. The decision to replace the MD-lls with as many as 20 Airbus Industrie A340-300s was the culmination of a long- running saga involving perform ance degradation on the PW4051s powering SIA's A310- 300s, and exacerbated by the excessive fuel-burn logged on MD-lls powered by the PW4460. Although SIA says the cancellation was simply due to the MD-ll's inability to meet payload/range targets for specific missions such as Singapore- Paris, it appears that the airline was determined to teach both Douglas and P&W a lesson for months of con fusion over the actual perform ance that the aircraft would deliver. McDonnell Douglas and P&W were in formed offi cially of SIA's decision to can cel the MD-lls at a meeting in Singapore on 23 July. Although both companies revealed new performance figures indicating that the MD-11 would indeed meet the Singapore-Paris mis sion, after a series of engine and airframe modifications, SIA's management was not impressed. The main problem was the high fuel-burn on the PW4460- powered versions of the MD-11, first noticed at the start of the flight-test programme early last year. Although GE also exceeded its fuel-burn targets, P&W was found to be 6.7% above its contract guarantees, putting the aircraft some way short of SIA's very demanding payload/range specification for the Singapore- Paris service, the benchmark mission upon which the MD-11 order was based. Singapore-Paris nonstop is one of the most difficult long- haul routes anywhere, with the 12,352km (6,677nm) great- circle distance compounded by the average 80-90kt (150- 170km/h) winds on the west bound leg. SIA's specification was even more demanding, with the airline insisting on its own unique "padding" on top of the international standard of 5% for weather contingencies. This pad ding amounts to more than dou ble that of the international standard and includes 4% to allow for engine and airframe deterioration over service life. The payload/range target of 28.6t over 12,352km was within the original capabilities of the MD-11, based on pre-flight esti mates, but be yond its reach once the high fuel-burn was discovered. The original generic guarantees for the MD-11 speci fied that the air craft would be able to carry a payload of 27.68t over a distance of 12,950km, but the excessive fuel-burn reduced this weight to 22t over the maximum range. Douglas introduced the drag reductions out of frustration at the failure of both engine com panies to meet their perform ance guarantees. Although both suppliers announced engine im provements quickly, the long lead-times involved meant that significant reductions in fuel- burn would not be available until at least the end of 1992, with P&W's four-stage product improvement programme (PIP) not due to be completed until late 1994. The aerodynamic modification package, known collectively as the Model A-l configuration (Flight International, 7-13 Au gust), is due to reach the pro duction line in mid-1993. Ac cording to flight-test re sults, it will re duce airframe drag to the point where the MD-11 will meet, and in some cases exceed, its original payload/range estimates, when combined with either GE's or P&Ws 'o,wn engine-improve ment programmes. In the case of the Singapore- Paris mission, however, Douglas was forced to admit to SIA that without a 7,400 litre (1,950 USgal) belly-mounted auxiliary fuel tank, the MD-11 would fall 555km short of the specified range, with a 28.6t payload. This conclusion was reached after in dependent auditors, hired by Douglas, rejected P&W's assess ment of a 5.7% improvement in fuel-burn efficiency through the four-stage PIP, deciding instead that the best P&W could hope for was a 2.5% recovery by 1994. The low credibility which Douglas attached to P&Ws esti mates also lay behind the aborted wing-stretch study which MDC chairman John McDonnell outlined to SIA at a meeting in April (Flight Interna tional, 29 May-4 June). Al though the 3.2m "Singapore Wing" stretch would have recov ered the lost range even without Pratt's PIP, it would have in volved changes to about 60% of the wing engineering drawings. The stretch would have been very expensive, was not retrofit- table, and would also have caused problems fitting the MD- 11 into DC-10 gates. With hindsight, Douglas sources believe that revealing this incomplete study to SIA increased the airline's exaspera tion with the two companies, contributing to an overall im pression of con fusion and disar ray. This impres sion was rein forced by the disagreement over the pros pects for Pratt & Whitney's PIP, and the differing performance figures this pro duced. The irony ol the SIA story is that the PW4460 remains, on paper, the most efficient engine for the MD-11, as Japan Air Lines has just reiterated. Com pared with GE's CF6-80C2, it is lighter, based on newer technol ogy (the CF6 core is now more than 20 years old) and, when the PIP comes to fruition, promises to burn fuel more economically. Unfortunately for Pratt & Whitney and Douglas, SIA was no longer willing to listen to promises — at least not from them. Although SIA did look at "very detailed data" on the CF6- powered MD-11, the option of simply switching engines was rejected because GE was also failing to meet its performance guarantees. The final irony for Douglas and P&W is that SIA has ex changed one set of. promises for another by agreeing to launch the A340-300, an aircraft which has yet to fly. The onus is now on Airbus and CFM to demon strate that their promises hold more water than those of their US competitors. • BY JOHN BAILEY "The airline was determined to teach Douglas and P&W a lesson for months of confusion" "The irony is that the PW4460 remains, on paper, the most efficient engine for the MD-11" 18 FLIGHT INTERNATIONAL 14 - 20 August, 1991
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