In simplistic terms, the base check part of the MPD for the 767 family comprises a series of four C checks in a cycle, covering system, and structural and corrosion prevention and control programme (CPCP) tasks. They combine in various ways to create 12 checks – C1 to C12. The big checks are C4 (first base cycle), C8 (second base cycle), and C12 (third base cycle) (at 24,000 flight hours, 48,000 FH and 72,000 FGH respectively) and these are the equivalent of a ‘D’ check. There are also zonal tasks, which can be grouped with either system or structural tasks as necessary.
The routine inspections and non-routine defects for the four checks in the second base cycle (checks C5 to C8) total 23,000-24,500 manhours (MH), and increase to 27,000-28,500MH in the third base cycle (checks C9 to C12). Stripping and painting the aircraft adds about 2,500MH, and is done every 5 years or so. Interior refurbishment, galleys and toilets refurbished, and seats refurbished and even recovered will add another 4,500-5,500MH.
The total MH consumption for the C checks adds to the region of 36,000MH for the second base check cycle, and up to about 40,000MH for the third base check cycle. For most aircraft, the end of the third base cycle (and check C12) should correspond to 15-16 years age.