et. al. report maximum tail buffet at 22° angle of attack for full-scale
flight tests and for a scale model with elastically scaled tails.
Comparing the GT model's maximum spectral peak intensity with angle of
attack, we get the axis on the right in the figure. At angles of
attack less than 22°, this comparison suggests that low intensity but
narrow-band fluctuations drive the tails to their maximum buffet.
Also, buffet is actually reduced as spectral intensity dramatically increases
at higher angles of attack. This illustrates the need to measure
the velocity fluctuations present in the vertical tail flow field on an
F-15. Tail accelerometers measurements are dominated by the response
motion of the structure. Tail fluctuating pressure data also are
dominated by the response tail motion. Off body velocity measurements
will show the fluctuations that are the primary drivers of tail buffet.