Flight Loads Spectra of a Fleet of Heavy Air Tankers

Abstract

In-flight recorded data from eight BAe-146s and eight RJ-85s flown in support of the United States Forest Service aerial firefighting operations have been analyzed. Flights have been divided into firefighting, ferry, and maintenance/training missions. Firefighting flights have been divided into five separate phases. The recorded normal accelerations have been filtered to remove the frequencies due to structural vibration and have been divided into gust and maneuver loads using the two-second rule. Using the method of peaks-between-means, exceedance spectra for gust and maneuver loads have been developed for ground-air-ground cycles, as well as for specific flight phases. The results have been compared with those of the legacy air tankers and other aircraft flown in support of firefighting missions and as civil transport. The maneuver load factor spectra are shown to indicate smaller loads than those of legacy air tankers, but exceeding considerably in frequency those of civil transport.