[schwarze-man]

Another factor that would impinge upon aero engine build man hours (and overall cost) that might be important statistically, is the quality control of finished engines that requires endurance testing and subsequent strip/rebuild/examination before final test and issue. Rolls-Royce certainly did this with all new Merlin types and production plants for a certain amount of production. Alec Harvey-Bailey states that even after satisfactory production was established, a certain amount of engines were still given the full test strip-down proceedure. Obviously, the initial production engines would incur a considerable production effort penalty. Details of German production QC of aero engines are even more difficult to quantify. Daimler Benz certainly worked through many test engines in development work. When a new engine type went into production, it was initially produced in a 0 series that had a shorter overhaul life. I have no information about the strip testing of production engines but, I would expect it was done in a similar way to RR until late in the war, for instance, the latest DB605 I have seen with an 0 series designation is an Autumn '44 built DB605DM-0.
Overall, these sort of extra factors would make differences to the production cost that might or might not be included in quoted statistics. Cheers

SM