An earth boring apparatus at least partially locatable within a borehole. A flight simulator program determines a sum of the pitching moments acting on the simulated aircraft, excluding the user setting of the elevator. The developer image detection part detects the mark developer image moving on a carrying path that is from a primary transfer position to a secondary transfer position, and the drive controller controls carrying of a medium based on a detection result of the mark developer image by the developer detection part. The retractable member can be configured to receive the protruding member in a mechanical coupling.