CAT cannot be seen, because there is no moisture at the altitude at which it occurs. In the lower altitudes, where there is moisture, turbulence in the air causes recognizable cloud patterns.
catalyst. A substance used to change the speed or rate of a chemical action without being chemically changed itself.
Water functions as a catalyst in the process of iron turning into rust (iron oxide). Dry iron does not rust nearly as fast as iron with water on its surface. The water itself is not affected, but the iron unites with oxygen from the air to become iron oxide, or rust.
catalytic cracking (petroleum refining). A method of refining petroleum products. In catalytic cracking, a catalyst is used to change high-boiling-point hydrocarbons into low-boiling-point hydrocarbons.
catapult. A mechanism used to hurl, or launch, an object at a high rate of speed. Catapults are used to launch heavily loaded aircraft from the decks of aircraft carriers.
category (aircraft classification). 14 CFR Part 1:
“(1) As used with respect to the certification, ratings, privileges, and limitations of airmen, means a broad classification of aircraft. Examples include: airplane; rotorcraft; glider; and lighter-than-air; and
(2) As used with respect to the certification of aircraft, means a grouping of aircraft based upon intended use or operating limitations. Examples include: transport, normal, utility, acrobatic, limited, restricted, and provisional.”
Category A. 14 CFR Part 1: “With respect to transport category rotorcraft, means multiengine rotorcraft designed with engine and system isolation features specified in Part 29 and utilizing scheduled takeoff and landing operations under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight in the event of engine failure.”
Category B. 14 CFR Part 1: “With respect to transport category rotorcraft, means single-engine or multiengine rotorcraft which do not fully meet all Category A standards. Category B rotorcraft have no guaranteed stay-up ability in the event of engine failure and unscheduled landing is assumed.”
Category II operations. 14 CFR Part 1: “With respect to the operation of aircraft, means a straight-in ILS approach to the runway of an airport under a Category II ILS instrument approach procedure issued by the Administrator or other appropriate authority.”
Category III operations. 14 CFR Part 1: “With respect to the operation of aircraft, means an ILS approach to and landing on, the runway of an airport using a Category III ILS approach procedure issued by the Administrator or other appropriate authority.”
catenary curve. A curve formed by a flexible cable suspended between two points at the same level.
cathedral (aerodynamics). Negative dihedral. The wings of an airplane, as they are viewed from the front, are not usually straight; they normally angle upward from the center. This upward angling is called positive dihedral, and it improves the stability of the airplane.
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