HP cock

HP (high-pressure) cock

The cock(s) used to stop the engine by cutting off the fuel supply to the burners. These may be electrically or manually controlled and are usually incorporated into fuel control units to eliminate unnecessary pipe connections. Unlike the low-pressure (LP) cock, which cuts off fuel supply from the aircraft fuel system, the HP cock cuts off fuel supply from the HP pump(s).
hub
i. The portion of a propeller where the propeller blades are fastened. The hub is attached to propeller shaft of the engine.
ii. The chief airport of a major city, which acts as an intermediate station where flights from various stations merge and radiate out in a hub-and-spokes arrangement.
iii. A classification of airports in terms of passenger enplanements. Large hubs are those airports with passenger enplanements of more than 1% of the country's annual enplanements. Airports are classified as medium hubs if their share is between 0.25 and 0.999% and small hubs if this percentage is between 0.05 and 0.249. Airports with less than a 0.05% share of annual passenger enplanements are classified as no hubs.
human engineering The activity or science of designing, building, or equipping mechanical devices or artificial environments to the anthropometric, physiological, or psychological requirements of the men and women who will use them.
human factor principles Principles that apply to aeronautical design, certification, training, operations, and maintenance and that seek safe interface between the human and other system components by proper consideration to human performance (ICAO).