Finalizing Wing Design Parameters
Sections 3.11 through 3.20 cover a wide range of wing design features. This section describes the considerations necessary to finalize the wing design. Selection of the aerofoil is the most important initial task. The wing aerofoil t/c ratio is established for the maximum cruise speed by the choice of aerofoil and sweep. It can vary along the span, with the root demanding the thickest section to withstand the bending moment. Once the aerofoil is selected, six parameters must be established for wing design: (1) wing planform area, (2) wing aspect ratio, (3) wing span, (4) wing sweep, (5) wing dihedral, and (6) wing twist.
1. Establish the wing reference area (see Chapter 11).
2. Establish the wing planform geometry (i. e., the maximum aspect ratio permitted by the structural technology). The statistics provided previously are a good guide. A new design should have higher aspect ratios compared to current designs.
Figure 3.46. Horizontal tail and vertical tail
3. Establish the wing sweep for the Mach number of operations.
4. Establish the wing span from the previous three steps. For commercial transport aircraft, the wing span is currently restricted to a maximum of 80 m.
5. Establish the wing dihedral and anhedral angles; it is generally within 1 to 5 deg for the dihedral.
6. Establish the wing twist; it is usually within 1 to 2 deg (generally downwash).
At the conceptual stage, the twist, dihedral, and anhedral are taken from experience. Subsequently, CFD analyses can fine-tune all related parameters for the best compromise. Ultimately, wind-tunnel tests are required to substantiate the design.