Technology Update
January/February 2002
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Longer-range 747-400 design nears completion
 The Longer-Range 747-400 airplanes are the same size as the current 747-400 model, but they allow airlines and cargo carriers to fly longer routes, or carry more cargo or passengers on existing routes. |
Boeing Co. engineers have completed 90% of the design work for both the passenger and freighter versions of the new Longer-Range 747-400 family of airplanes. According to the company, the first of these airplanes begins major assembly in February 2002, rolls out of the Everett, WA, factory in June and, after a four-month flight test program, will be delivered in October 2002 to launch customer Qantas Airways.
The Longer-Range 747-400 airplanes are the same size as today's 747-400s, but they allow airlines and cargo carriers to fly longer routes, or carry more cargo or passengers on existing routes. To support this enhanced capability, Boeing has increased the aircraft's gross takeoff weight by 35,000 lb to 910,000 lb.
An auxiliary tank in the airplane's lower lobe provides fuel for the airplane's additional range capability; an optional second tank is available as well. Using both auxiliary tanks and fuel in the horizontal stabilizer (on the passenger version), the Longer-Range 747-400 will be able to carry up to 63,765 gal of fuel. Supporting the gross weight increase are strengthened parts of its wing, fuselage, and landing gear, which includes new tires and wheels.
 The general arrangement of the Longer-Range 747-400 is identical to the 747-400. Click to enlarge |
The passenger version of the new aircraft can fly an additional 435 nmi or carry an additional 15,000 lb of payload, either in the form of extra cargo or a full load of 416 passengers.
The first freighter of the long-range aircraft will be delivered in October 2002 to International Lease Finance Corp. and operated by Air France. The takeoff weight increase allows the airplane to fly an additional 525 nmi or carry an additional 21,000 lb of payload on long-range flights at maximum takeoff weight. With the additional takeoff weight capability, the Longer-Range 747-400 Freighter will be able to carry 134 tons of cargo.
"These are just the latest improvements to the 747, but certainly not the last," said Jeff Peace, 747 Vice President and General Manager. "We continue to talk to customers about the next set of improvements—and the ones after that." Among the features, options, and capabilities under study are airplane-noise reductions to meet the latest environmental rules, flight-deck enhancements for improved operational efficiency, and a redesigned interior architecture for passengers as they enter the airplane.
- Frank Bokulich
NASA studies wingtip vortices
 Two NASA FIA-18 aircraft were used to demonstrate the fuel and range benefits of formation flying. |
A NASA F/A-18 jet flying in the wingtip vortex behind another F/A-18 achieved a 12% fuel savings at cruise altitude. The two aircraft, part of the Autonomous Formation Flight (AFF) project based at NASA's Dryden Flight Research Center in Edwards, CA, flew the mission in early December.
During the 96-min flight, the trailing aircraft, which was located 55-ft or one aircraft length behind the lead aircraft, burned about 600 lb less fuel than a third F/A-18 that flew outside the formation. The savings demonstrated that the aircraft range could have been extended more than 100 nmi while flying in formation. These results were verified with a second flight.
The goal of the AFF project is to demonstrate sustained 10% fuel savings of the trailing aircraft. The project seeks to extend the symbiotic relationship of migrating birds to manage formations of aircraft. The traditional "V" formation allows each bird flying aft of the lead bird to reduce drag and conserve energy.
The latest flight was performed so that the lead aircraft's wingtip vortex effects on the trailing aircraft could be mapped. Wingtip vortex is a spiraling airflow from the wing during flight, which causes rolling, yawing, and pitching moments on the trailing aircraft that must be counteracted with changes to the aircraft's control surfaces. These moments made it difficult for the trailing pilot to maintain proper position while flying in the vortex.
"What makes the flying difficult is we are deliberately flying in the presence of the wingtip vortex off the lead aircraft," explained NASA Dryden test pilot Dick Ewers. "This means the aircraft is being buffeted around and influenced by the airflow of the lead aircraft. We are using radio calls from the ground to confirm our nose-to-tail separation. After 30 seconds to a minute or more in one position, we readjust five or so feet to a new precise position for the next data point. Do this for an hour, and one is very relieved to head back for a landing."
Vortex modeling represents a significant portion of AFF research. The most desirable scenario is for an aircraft's autopilot to control the formation. The models from the F/A-18 formation flights will enable control engineers to design and test an autonomous autopilot system. The model will also be used to predict the aerodynamic interactions between two aircraft. Testing of the formation autopilot is the goal of the next flight phase, scheduled for the summer of 2002.
Although fighter-type aircraft are being used for the technology demonstration, commercial or military transport aircraft as well as uninhabited aerial vehicles (UAV) can realize formation flight fuel savings and drag reduction. However, these aircraft would need to fly five to six aircraft lengths behind the lead aircraft.
Parts of this article were provided by Beth Hagenauer of the NASA Dryden X-Press.
