Assessment of Wingtip Modifications to Increase the Fuel Efficiency of Air Force Aircraft (2007) / Chapter Skim
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2 Wingtip Modifications
2 Wingtip Modifications
Pages 18-30
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From page 18... ...
2 Wingtip Modifications HISTORy OF WINgTIP DEVICES Within a few years of the first heavier-than-air flight, the idea of beneficial wingtip devices was introduced. Lanchester patented the concept of a wing end plate in 1897 and suggested that it would reduce wing drag at low speeds.
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From page 19... ...
The winglet of the Boeing 747-400 has a much lower dihedral angle than the Whitcomb winglet, and since that time, numerous vertical, canted, and horizontal wingtip extensions have been put into commercial and military service, as shown in Figure 2-1. INTRODuCTION TO WINgTIP AERODyNAMICS Much of the drag of an aircraft is related to the lift generated by its wing.
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From page 20... ...
0 FIGURE 2-1 Wingtip modifications with a variety of geometries have been tested and deployed on both commercial and military aircraft. SOURCE: Courtesy of Doug McLean, "Wingtip devices: What they do and how they do it," Presentation at the Boeing Performance and Flight Operations Engineering Conference, September 2005.
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From page 21... ...
So, perhaps the simplest means to reduce induced drag is to increase wingspan through horizontal wingtip extensions. However, in some cases this modification may not be appropriate because of explicit geometric constraints such as hangar width; in others it may not be desirable because of the increased structural weight of the wing, which must be designed to carry greater bending loads.
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From page 22... ...
Thus, the benefit associated with the tip device will depend on the specific aircraft and the structural margins of the wing. Finally, the wingtip device adds weight that comes not only from the device itself and its attachment fitting but also from any structural modifications to the existing wing to allow it to handle the additional static loads and to meet flutter and fatigue requirements.
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From page 23... ...
Retrofitting existing wings may be the lowest cost option in the near term. This option is especially attractive for aircraft having substantial structural margins.
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From page 24... ...
Some aircraft growth versions have included both tip extensions and root plugs (DC-9 Series 50 to MD-80) .12 This approach involves more substantial modification of the wing but can produce greater fuel savings than simple tip modifications, adding wing area and permitting higher root bending loads than would be possible with tip changes alone.
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From page 25... ...
. Figure 2-3 shows the increase in payload-range capability made possible by winglets on 15Jay Inman, Vice President of Programs, Aviation Partners Boeing, "Blended winglets," Presentation to the Committee on Analysis of Air Force Engine Efficiency Improvement Options for Large Non-fighter Aircraft on June 14, 2006.
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From page 26... ...
Without Winglets Winglets FIGURE 2-3 Winglets increase payload-range capability of the Boeing 737-800. SOURCE: Aviation Partners Boeing, Presentation to the Committee on Analysis of 2-3 Air Force Engine Efficiency Improvement Options for Large Non-fighter Aircraft on Background removed, requiring removal of X an Y axes June 14, 2006.
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From page 27... ...
The wing modification costs depend on specific wing characteristics, including structural margins and loadings, as well the strength remaining in light of structural fatigue and corrosion. The wing modifications required to accommodate a tip device could be extensive.
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From page 28... ...
21Jay Inman, Vice President of Programs, Aviation Partners Boeing, "Blended winglets," Presentation to the Committee on Analysis of Air Force Engine Efficiency Improvement Options for Large Non-fighter Aircraft on June 14, 2006.
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From page 29... ...
For the same aerodynamic improvement, winglets typically add less span to the airplane than a wingtip extension and might enable the continued use of existing ramp space, gates, hangars, etc. Interference with Other Wing Equipment Wingtip modifications might also impact other wing requirements.
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From page 30... ...
0 ASSESSmENt oF wINgtIP modIFICAtIoNS aircraft, the Air Force should embark on putting wingtip modifications on its mobility aircraft. Investigating the viability/efficacy of such modifications is of value, and a lot can be learned from the extensive work that has already been done on commercial aircraft.
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