Components: Each model has data for major drivetrain component intervals and schedules.

Hourly Maintenance Costs (HMC): HMCs can be found on the components tab of the Blue Book. Hourly Maintenance Cost (HMC) is the expense of running a helicopter’s major components for one hour. The HMC includes the parts and labor required for scheduled and unscheduled maintenance and inspections that are performed every twenty-five flight hours or greater. Maintenance intervals less than twenty-five flight hours are not considered. HMCs are determined by computing the cost of each major-drive train component’s overhaul and retirement interval, with its associated labor costs, then dividing that sum by its allowable flight hours. The resulting perhour costs are then totaled. HMCs are given as a range due to the variation of parts costs, transportation and labor charges, and discounts. Operators that do not employ in-house certificated maintenance technicians will likely have a higher HMC.