Ed Set, thanks for the comprehensive reply. I am trying to get my head round the BoI conclusions. AAR pressure was thought to be insignificant below 120psi, but no studies had been carried out on the cause of surges or the cumulative effect of surges. Ground testing equipment only tests up to 50 psi and the BoI have ordered that a 50psi limit be reintroduced.
This aircraft has been plagued by pressure surges and fuel leaks in recent times, many of them impossible to re-create on the ground. I just found it hard to understand why the 50psi limit was removed in the first place, when these conditions were not able to be re-created in controlled tests.