Design effort
Seven early customers, namely British Airways, Cathay Pacific, KLM, Lufthansa, Northwest, Qantas, and Singapore Airlines, formed a consultative group to advise Boeing on the 747-400's design process.[13] While the aircraft was planned as a new-technology upgrade, Boeing originally proposed minimal design changes in order to reduce development cost and retain commonalitywith existing models.[13] However, the airline consultative group sought more advanced changes, most notably a two-crew glass cockpit. As a result of airline input, the 747-400's new digital cockpit design featured a hybrid of the cathode-ray tube (CRT) display technologies first employed on the 757 and 767, along with carry-over 747 systems such as its autopilot.[13]
The 747-400's wingspan was stretched by 17 feet (5.2 metres) over the Classic 747 through wingtip extensions. For reduced aerodynamic drag, the wings were fitted with 6 feet (1.8 metres)-tall winglets.[14] Despite the added length, the wings were 6,000 pounds (2,700 kg) lighter as a result of new aluminum alloys.[14] The horizontal tail was also redesigned to fit a 3,300 US gallons (12,000 l) fuel tank, resulting in a 350 nautical miles (650 km) range increase, and the rudder travel was increased to 30 degrees.[14] The landing gear was redesigned with larger wheels and carbon brakes.[14]Internal changes further included a restyled cabin with new materials and updated fittings.[15]
New engines offered on the 747-400 included the Pratt & Whitney PW4056, the General Electric CF6-80C2B1F, and the Rolls-Royce RB211-524G/H.[14] The engines offered lower fuel consumption and greater thrust, along with a full-authority digital engine control (FADEC) which adjusted engine performance for improved efficiency compared with the Classic 747s.[14] A new auxiliary power unit (APU) manufactured by Pratt & Whitney Canada was also selected to provide on-ground power for the 747-400, with a 40 percent reduction in fuel consumption compared to previous APU designs.[14]
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