Turboshaft Efficiency Metrics FAQ

DOC encompasses fuel burn, engine reserve programs (power-by-the-hour), airframe scheduled maintenance, dynamic component overhauls, and lubricants. It does not include indirect costs like pilot salaries, insurance, or hangarage.

TBO is the manufacturer-specified operating hour limit for dynamic components (engines, gearboxes, rotor heads) before they must be removed and completely overhauled. Higher TBOs significantly reduce DOC.

The difference defines the useful load. A lower empty weight resulting from composite materials increases the allowable payload (fuel + passengers/cargo) for a given engine power rating.

Health and Usage Monitoring Systems (HUMS) use vibration sensors to track the wear on gears and bearings in real-time. This transitions maintenance from schedule-based to condition-based, increasing safety and availability.

Super-mediums (e.g., Airbus H175, Leonardo AW189) bridge the gap between medium twins and heavy lifters (like the S-92). They weigh between 7 to 9 metric tons and offer heavy-class payload ranges at medium-class operating economics.