Post-incident inspection shows the port cap shroud bottlescrew had 40% thread engagement remaining — the rest was corroded and the locking nut had not been wired. What maintenance failure does this represent?

A. Force 6 exceeded the design limit of the rig — this is expected equipment failure

B. Normalisation of deviance: the bottlescrew had been in this condition for at least 2 seasons (insufficient thread engagement, no locking wire) — it passed the annual rig check by visual inspection only. The skipper had sailed safely with it in this state until a Force 6 shock load caused failure. Two failures: inadequate inspection standard (visual only) and no locking wire allowing rig vibration to back off the bottlescrew over time

C. The manufacturer used substandard materials — a design defect, not a maintenance failure

D. The bottlescrew failure was unforeseeable — modern fittings should not require annual inspection