structural inspections of the pod with a mathematical analysis of the accumulated damage using a Fatigue Damage Spectrum (FDS) approach. The accumulated damage was calculated from the measured acceleration data and compared with the certified capacity of the pod to ensure that it did not encroach too far towards the certified level. A Shock Response Spectrum (SRS) analysis was also performed to ensure that no single high acceleration event would induce loads in excess of the design envelope.
nCode International were contracted to provide the necessary signal processing, fatigue analysis and Mission Profiling software. Together with the supplier they performed analyses to compare the FDS given for the fast jet flight envelope over a 20 hour flight trial with that of the certified sign-off test. A comparison between the PSDs is given in Figure 6; however, this simple comparison does not account for the differences in loading duration or the frequency response of any internal components. The ERS and FDS analyses are able to account for these parameters and are illustrated in Figure 7.