Acoustical Environment of an F-35B During Vertical Landings

Measurements of the sound field near an F-35B during vertical landing operations are reported. Data are presented and discussed from the approach, hover, and descent of the aircraft, and compared with ground run-up measurements. Overall levels are comparable to published values for the F-35A at 50% engine thrust ratio during ground run-ups. Onethird-octave spectra are also presented, and spectra from various stages of the approach and landing are compared. Changes in the spectral shape during the landing process are discussed and impingement is presented as a possible cause of these changes. The azimuthal directivity of the sound field during hover and descent are shown for the purpose of environmental modeling, showing slight directivity during the hover process and little to no directivity during the descent. An analysis of nonlinear propagation metrics gives values again consistent with those found for the F-35A operating at 50% engine thrust ratio during ground run-up.