Conclusions

A look at nonplanar wing concepts suggests that such configurations do offer potential performance benefits. This is especially true when the concept is fully exploited by resizing or even redesigning the aircraft.

In addition to reductions in vortex drag, some of configurations mentioned here have desirable effects on structures, stability and control characteristics, vortex wake hazards, and other practical considerations.

The split tip design demonstrates that by manipulating the wake shape as well as the wing shape, some of the advantages of nonplanar wings may be obtained even with planar wings, and the possible applications of this idea warrant further study.

The C-wing configuration remains an intriguing design concept with many beneficial characteristics when applied to a large aircraft design. The implications of this approach remain to be more fully explored.

Postscript

The direct application of these concepts to an existing aircraft are less than overwhelming. As illustrated in the figure below, if a 20% reduction in vortex drag were achieved by an existing airplane and the airlines passed the savings on to the customers directly, we would see a very modest reduction in ticket price (about $3 on a $300 ticket). Although this savings would have major implications for airline profitability, most passengers would not be impressed by the savings. If the concept is used to redesign the airplane, as in the C-wing example here, not only is the savings increased, but an otherwise infeasible design may become feasible.

The direct insensitivity of ticket price to drag might be exploited as shown below. By redesigning an aircraft with fixed payload capacity, but with twice the floor space for each passenger, the fare would have to be increased by about $30 on a $300 ticket (see note). This is very reasonable, but might still be unacceptable in the highly elastic commercial transportation market. Nonetheless it is my hope that advances in aerodynamics and other disciplines can be employed to do more than just marginally lower the cost of air transportation, but rather improve its safety and comfort.