Usage and flight loads analysis of King Airs in aerial firefighting missions

Abstract

Flight data of Beechcraft King Airs used as aerial supervision modules and lead aircraft by the U.S. Forest Service are analyzed. The operational conditions experienced by the airplanes are studied as well as the magnitude of the vertical loads. The airplanes are flown in four different types of missions in U.S. Forest Service operation. Data from 1853 flights and seven aircraft are presented. Spectra are shown for gust and maneuver loads, separated using the two-second rule. These are given for the entire flight for various mean sea-level altitudes. In addition, the combined loads are presented and compared to existing data and Federal Aviation Regulation 23. It is shown that these aircraft are operated well within their design envelope. It is demonstrated that, although gust loads are comparable to those outlined in Federal Aviation Regulation 23, the maneuver load frequencies far exceed those of typical airframe use. Although these results do not warrant changes to Federal Aviation Regulation 23, they highlight the need for modified airframe maintenance and inspection procedures as well as the estimated airframe fatigue life.