CAM data differs when it comes to airframe & engines. An engine can be changed for a new one or can be removed to be fixed. Different engines in the same aircraft have different history of their aircraft hours and cycles.
In this section you can define such values for each aircraft,as:
- Start date - the date of the first flight.
- Start TAH - total number of accumulated hours.
- Start TAC - total number of accumulated cycles.
Section 'Airframe' defines data for total TAH & TAC of the aircraft (without splitting on engines). That data is also displayed in OPS > Fleet screen, column 'Airframe'.
Because both TAH & TAC values can be different for different engines, you can specify exact data for each of four engines.
Enter each engine's serial number to activate this feature. Add start date, start TAH, start TAC and update the screen.
When you add a new flight on that particular aircraft, 'Airframe' TAH & TAC will get changed as well as TAH & TAC for each separate engine. To view it, hover the mouse over the icon 
in 'OPS > Fleet' section, and you will see exact information in the pop-up window (see example below).
You can also add seperate data for 'APU' (Aircraft Power Unit), however, APU hours and cycles do not get automatically increased from the journey log entries (like engines). With APU, Leon just stores the latest value you provide here, which should be updated every time you have the new one.