In all analysed vibration spectrums measured on the pilot’s seat,
PRF is observed together with its harmonics. The existence of 1st,
2nd, 3rd and 4th harmonics in all selected flight modes is obvious.
Since the aircraft Lasta is equipped with a two-blade propeller, BPF
coincides with 2nd harmonic of PRF, meaning that data of vibration
accelerations on the seat are the largest on 2nd harmonic of PRF.
The frequencies of engine rotation and aerodynamic propeller rotation
coincide on all higher even harmonics of PRF. Changes in flight
modes with maximum engine running speed impacts the vibrations
on the seat without vibration rubber absorber. That fact is
shown in Fig. Vibrations Analysis of PRF and its harmonics is done
while they are acting in the direction of axes X, Y and Z. Influence
of changes in flight profiles on vibration spectrums, on the seat,
during each harmonic in the direction of X and Z axes, is based
on changes in vibration accelerations caused by changing flight
modes, is large and has been clearly shown. Impact of flight profile
changes in Y axis is practically negligible, because dissipation of
acceleration values is small.