Wetted and Projected Area Relationships in Commercial Airplane Design

Using generally available geometric data, calculations of wetted and projected areas of major components, that is, wings, fuselages, empennage, and engine nacelles, for 55 airplanes were compiled into a database comprising four groups: commercial, supersonic, all-wing, and military airplanes. Attention is primarily focused on subsonic and supersonic commercial airliners, and the wetted areas of the components of each are discussed and shown to be reasonably estimated by simple functions of airplane geometry, like gross wing planform area, fuselage length and diameter. Comparisons of total wetted areas of 13 commercial airplanes and 5 military airplanes with results reported by 14 independent studies showed good agreement. Total wetted areas for all the airplanes were shown to be well-represented by simple functions of wing planform area S alone. Relationships between the projected and wetted areas of the commercial airplanes were explored to illustrate the implications for airplane design, including accommodation of fuselage stretch, trends in component wetted area fractions, correspondence of wetted areas to planform envelope—that is, the product of wingspan and fuselage length, relation of frontal areas to wetted areas, and application of a planform configuration parameter, B = (bAR)^3/16(1 + 3.5/AR^9/4)^−1/2, to estimation of (L/D)_max—and prediction of wetted area as a function of gross weight based on the square–cube relation between area and volume.