The current and continuing energy crisis points out the need for minimizing the fuel burned for a given
mission by any new aircraft. Two major design decisions which impact the fuel economy and airplane
efficiency are choice of wing geometry and cruise speed.

This paper is intended to help in understanding the potential payoff from the careful selection of these
interrelated design parameters. To accomplish this task, wings with advanced technology airfoils and
aerodynamic aspect ratios ranging from 9 to12 were evaluated at cruise Mach numbers of 0.7 and 0.8. Various
wing sweep and thickness combinations and small cruise Mach number perturbations were studied at the
selected Mach number to ensure proper wing design refinement for an efficient, fuel conserving airplane.

It was decided that existing statistical/parametric weight prediction methods were inadequate for the
controlled evaluation of wing geometry parameters over the extreme limits of interest in this study.
Therefore, the wings were defined sufficiently to provide detailed geometrical data for aeroelastic
structural analyses. Thirty flight and ground design load conditions were analyzed for each wing, and
critical design conditions were identified at each span wise analysis station. Structural wing box
weights were generated within a computerized analysis program, and complete structural wing weights
were obtained with secondary structure and non-optimum accounted by statistical/parametric methods.
Flutter and fatigue increments were obtained externally and added to the strength-designed wing weight.

These wing weights and their respective aerodynamic efficiencies were incorporated in airplane mission
performance analyses. Wing area, flight gross weight, and engine thrust were sized to perform a constant
payload/range mission for each wing geometry and Mach number studied. A configuration was selected
based on the best fuel economy and lowest direct operating cost.

The selected fuel and cost conserving wing design was characterized by a quarter chord sweep of 25 degrees,
was 8% thick outboard, and was designed to cruise at Mach 0.8. The selected aspect ratio was 12, with
aerodynamic benefits of new airfoil technology overcoming the structural weight penalties.

Due to detail design and operational requirements outside the scope of this preliminary design study,
the fuel and cost savings of 25% (nominal) shown in this paper should be regarded as potential limits of
savings possible within the parametric limits examined.