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Richard T. Whitcomb was an aerospace engineer at the National Advisory Committee for Aeronautics and National Aeronautics and Space Administration's Langley laboratory. His research linked aerodynamic geometry with measurements of pressure, drag and flow changes near the speed of sound. NASA's official profile identifies his area rule, supercritical airfoil and winglet work.^[ref]

His 1947 sweep investigation provides a concrete earlier example. A wing was tested with zero, forward and backward sweep in the Langley 8-foot high-speed wind tunnel. Pressure measurements and wake surveys supplied loading and drag information, showing that changes associated with shocks were delayed by sweep without following a universal cosine shift exactly.^[ref]

For the area rule, the scientific question was whether the streamwise area distribution of the complete wing-body combination mattered more than judging each component separately. NASA describes testing his proposed distribution with a specially built wing-body model, then applying the result to a fighter configuration.^[ref]

An original bookkeeping example illustrates the geometric idea without predicting wave drag. If a body contributes $2.0{\mathrm{m}}^2$ of cross-sectional area at one station and the added wing contributes another $0.5{\mathrm{m}}^2$ to the stipulated combined section, their sum is $2.5{\mathrm{m}}^2$. Reducing the body's contribution to $1.5{\mathrm{m}}^2$ restores a $2.0{\mathrm{m}}^2$ total there. The relevant research concerns how that total varies along the vehicle; this one-station sum is not a drag law.

His later supercritical airfoil and winglet contributions addressed different flow mechanisms. NASA describes a shaped high-subsonic section and carefully tailored wing-tip devices, rather than treating every drag reduction as the same geometric correction.^[ref] The common experimental method is to specify the geometry, identify the predicted flow change and measure the resulting aerodynamic response.

The winglet cant angle specifies the inclination of a winglet away from a stated reference direction. Here $\varphi =0$ means an upright winglet, with positive $\varphi$ tilting outward from vertical in the transverse plane. A convention measured upward from the main wing plane would instead give $90{}^{\circ }-\varphi$ for this ideal geometry. A quoted angle therefore needs its reference plane. Winglet toe angle concerns a different orientation, involving the chord and incoming flow.

For a straight unswept winglet of length $\ell$, the purely geometric projections areIf symmetric winglets attach at the tips of a main wingspan $b$, their outer-tip projected separation is $b+2\ell \sin \varphi$. With stipulated $b=10\mathrm{m}$, $\ell =0.60\mathrm{m}$ and $\varphi =20{}^{\circ }$, the vertical height is $0.5638\mathrm{m}$, each tip moves outward $0.2052\mathrm{m}$, and the total projected separation is about $10.4104\mathrm{m}$. None of these projections alone supplies a new span efficiency factor or a prediction of lift-induced drag.

Cant also changes how loads act on the supporting wing. In a right-handed frame with $y$ outward, $z$ upward and $x$ completing the triad, the rolling-moment contribution of an applied force is $M_x=y{F}_z-z{F}_y$. For a stipulated $200\mathrm{N}$ vertical force applied at the outer tip, the moment about the vehicle centreline is $1000\mathrm{N}\mathrm{m}$ when the winglet is upright and about $1041.0\mathrm{N}\mathrm{m}$ at the stated outward cant. This isolates the changed moment arm; an actual aerodynamic load need not stay vertical or keep the same magnitude when cant changes.

Richard T. Whitcomb's primary design discussion explicitly balances lift-induced drag, skin friction and wing bending moments, and discusses outward cant separately from incidence and twist. It also identifies interference at the upper-winglet root as part of the design problem.^[ref] A controlled wind tunnel comparison must therefore record forces and moments at matched conditions, rather than infer an optimum cant solely from the projected span.