1995
True, but the three flying for Conocco stopped flying for over a year and were subject to seat reduction and other modification before returning to service(until 1995). They stopped flying altogether in the UK sector.
I draw the comparison because the chinook has proved itself as a very effective and safe machine. Many pilots and crew liked it.
However, the majority of offshore passengers didn't like it and decided they did not want to fly the type offshore. Apart from the three in Norway from 87-95, it stopped flying offshore.