"Periodic" is concerning....once every fifty years? Not!
To be sure, I am not familiar with the full suite of CARs for maintenance. There would have to be some sort of trigger to progress to NDT using X Ray examination. The case in question would indicate...corrosive environment, drains blocked or open to atmosphere, integrity of structure indicates weaken of joints..rather than a calendar date in service.
Last edited by OZBUSDRIVER; 2nd Sep 2015 at 20:50.