Spiroid Winglets, which look like a large loop of rigid ribbon material attached to each wingtip, cut fuel consumption by 6% - 10% in cruise flight. Initial flight tests of the Spiroid concept on a GII reportedly reduced cruise fuel consumption by more than 10%. The Spiroid eliminates concentrated wingtip vortices, which represent nearly half the induced drag generated during cruise.
The patented Spiroid-Tipped Wing* introduces a substantial change in design direction for wing tip devices that control vortices generated by lifting surfaces. As with any wing tip device, the objectives are to minimize airplane drag and improve performance throughout the flight envelope. Concentrated tip vortices in the wake of conventional planar wings produce high cross stream velocities and wasted energy which is associated with lift induced drag. Winglets are wing-like tip devices which reduce the vorticity strength and concentration thereby reducing drag. The Spiroid concept, featuring a closed contour, carries this trend to its logical conclusion, eliminating concentrated vorticity and further reducing drag.
Minimum induced drag for any lifting system requires an optimum aerodynamic surface loading and the Spiroid-Tipped wing is no exception. To accomplish this, appropriately matched airfoils for the twisted and cambered Spiroid surface are essential. Furthermore, to minimize friction drag, the Spiroid chord distribution must be held to lower limits but matched to the loading, while maintaining buffet margins. However, if this is carried too far, the resulting flexible structure may distort excessively under load thereby causing performance loss or dynamic problems. Adverse high speed effects which are associated with shock waves and flow separation can be avoided by appropriate airfoil selection and placement of the Spiroid segments in relation to themselves and also, to the wing. The Spiroid must also be appropriately sized for the intended application. The added weight and skin friction drag, which is the price that must be paid for induced drag reduction, are closely tied to geometry, structural load and design approach. For a given wing, there is an optimum Spiroid geometry which will minimize drag without exceeding wing structural capability. Normally, this will result in an overall span reduction which may also be seen as a benefit. However, if the wing has structural capability not currently being utilized, the ultimate drag benefit can be even greater but with somewhat increased span. Obviously there are many ways to exploit the tradeoff between drag, span, structural margins and wing weight; the designer's role being to select the appropriate combination for a specific application. Flight testing of Spiroids on a Gulfstream II aircraft within the normal flight envelope has shown impressive performance gains (e.g., more than 10% drag reduction) relative to the basic aircraft. Also, preliminary exploration of the vortex wake behind the Spiroid from a chase aircraft has indicated the potential for large decreases in wake intensity. This could substantially alter requirements for separation distances between lead and following aircraft in airport traffic patterns. As a result of this testing to validate concept applicability and resolve design issues, the potential of wing tip devices has greatly expanded for fixed-wing aircraft. Also, it is expected this new technology development will ultimately provide superior performance gains as well as operational benefits (e.g., increased safety, less noise, smaller space needs) in many applications where lifting surfaces are employed.
* Patent # 5,102,068.
©
, All Rights Reserved