One of our Canberra's is sent to an MU in Wales to have some new radar gear fitted and the pilot that flew it back reported the G4 compass as faulty, an air pocket or a turn would send it crazy. It was removed and taken to the instrument section and was found in perfect order. Warning bells rang, the port wing tip was the home of the flux detector for the G4 compass. The cover plate was removed and rolling around, sharing the same cavity as the flux detector, was a 6" x 1" stainless steel bolt. Evidently, while the tank was being refitted, a mounting bolt was dropped into the cavity and rather than take panels off to look for it, a new one was drawn from stores. The MU was Llandow and has now closed, I will relate another one of their boobs another time.
Ken







