Improved range for the Global Express will put pressure on Gulfstream
Bombardier has increased the range of its Global Express business jet by 370km (200nm), to 12,400km at Mach 0.8, following initial flight-testing of the first aircraft. The move increases pressure on Gulfstream, which admits that its rival, the GV, while slightly exceeding its 12,000km range guarantee, is overweight and that the programme is running behind schedule.
John Holding, Bombardier Aerospace executive vice-president, engineering and product development, says that the Global Express range was increased after accurately measuring the wing-tank fuel volume in the first aircraft. This confirmed that the fuel required for the 12,000km design mission could be housed entirely within the wing, he says, allowing an aft-fuselage tank added during design to be used for additional fuel to extend range.
Weight and drag measurements on the first aircraft confirm predictions, and, coupled with the better-than-predicted specific fuel-consumption (SFC) of the BMW Rolls-Royce BR710 turbofans, makes Bombardier "very comfortable" that it will meet or exceed performance guarantees for the Global Express, Holding says. The additional fuel will allow the 12,000km design mission to be accomplished at M0.85, instead of the original M0.8.
To accommodate the increased range, Bombardier will certificate the Global Express at a maximum take-off weight of 42,500kg, an increase of 1,150kg. The structure and landing gear are already designed to cope with the higher weight, he says. Take-off distance on a 12,400km flight will be 1,700m (5,500ft) compared with 1,500m for the 12,400km design mission.
Bombardier displayed the Global Express at the NBAA show, after accumulating some 40h flying in 16 flights of the first aircraft. Gulfstream, meanwhile, displayed the fifth GV- the first with a completed interior. The company has completed more than 930h of a planned 1,200h flight-test programme, and is aiming for certification by the end of this year - later than planned.
Gulfstream Aircraft president Bill Boisture admits that initial customer deliveries will be 30-60 days behind schedule, but he hopes to be back on plan by mid-1997, after delivery of ten to 20 aircraft. Reasons for the delay include the need to rework early wings after analysis revealed a weak spot. Risk-sharing wing supplier Northrop Grumman is reinforcing stringers on the upper surface, adding 30-35kg to aircraft weight.
To accommodate this and other weight increases, Gulfstream has increased the maximum take-off weight at which the aircraft will be certificated to 41,100kg, from 40,400kg. The company says that the GV will still exceed its 12,000km-range goal at this weight, because of the aircraft's design margins, the BR710 engines' better-than-guaranteed SFC and a 135kg increase in fuel capacity.
Gulfstream says that the GV's cruise speed, specific range and take-off and landing distances are bettering guarantees. Bare empty weight is worse than the guarantee by about 680kg, but the company says that efforts are under way to reduce the weight of the airframe and power plant.
Gulfstream has flown the first production GV and plans to deliver the aircraft to the completion centre by the end of 1996. The company says that it holds 70 firm orders for the aircraft, while Bombardier says that it has "close to 60" orders for the Global Express, which is scheduled for certification in May 1998.
Gulfstream says that it plans to double its production rate to 60 GIV-SPs and GVs a year by 1999, to meet demand.
Source: Flight International
