Gone Tomorrow, Pt. 2

S4, E2: All Sam's skills are required when 10 more bodies are recovered from the North Sea, and the piecing together of the jigsaw of evidence begins in earnest with her pathology team. The discovery that a new rotor bolt was fitted to the crash helicopter recently and that the files are not up-to-date raises more questions. Who supplied and fitted the parts, and did the pilot and engineer sign them off?