Term or Terms  Definition 
conducted.  Each local flying area should be defined in a manner acceptable to the operator, the local Flight Standards District Office, and the Principal Operations Inspector, taking into account the operating environment, the geographic terrain features, and the capabilities of the aircraft. 
Major Contract Training  Any flight training, flight testing, or flight checking leading to and maintaining certification and qualification of air carrier flightcrew members in accordance with the requirements (maneuvers and procedures) explicitly stated in 14 CFR Parts 61, 121, or 135; or in SFAR 58 Advanced Qualification Program (AQP), as applicable. 
Medical Crewmember  A person with medical training who is assigned to provide medical care and other crewmember duties related to the aviation operation during flight. 
Minimum Descent Altitude (Height)  MDA(H) is the lowest altitude in an instrument approach procedure to which a descent is authorized on final approach or during circle-to-land maneuvering.  The 'altitude' value is typically measured by a barometric altimeter; the 'height' value (H) is typically a radio altitude equivalent height above the touchdown zone (HAT) or height above airport (HAA) published elevation.  The (H) is used only for advisory reference and does not necessarily reflect actual height above underlying terrain. [This definition is consistent with both current U.S. operator usage and ICAO international agreements.] 
Operational Service Volume  The Operational Service Volume is that volume of airspace surrounding a NAVAID which is available for operational use and within which a signal of usable strength exists and where that signal is not operationally limited by co-channel interference.  Operational Service Volume includes all of the following: (1) The officially designated Standard Service Volume excluding any portion of the Standard Service Volume which has been restricted.