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technical development of aviation and was superseded in October of 1958 by NASA, the National
Aeronautics and Space Administration.
NACA cowling (reciprocating engine cowling). A long-chord ring cowling whose trailing edge fairs
smoothly into the fuselage or engine nacelle. NACA cowlings are used on the vast majority of modern
radial engine installations.
The cooling air rams into the open front of the cowling and exits through an annular slot at the rear.
This slot is often covered with adjustable cowl flaps to control the amount of cooling air allowed to flow
through the engine. The airfoil shape of the cowling produces a forward aerodynamic force that more than
compensates for the cooling drag of the engine.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 396
nacelle. An enclosed compartment in an aircraft in which an engine is mounted. Most multiengine
propeller-driven airplanes have engine nacelles mounted on the leading edge of the wings far enough out
that the propellers clear the fuselage.
Multiengine jet-propelled airplanes often have their engines mounted in nacelles on the sides of
the fuselage between the wing and the tail, or in nacelles hanging below the wings. Nacelles in which jet
engines are mounted are often called pods.
nailing strip. A method of applying pressure to the glue in a scarf joint repair in a plywood skin. A strip of
thin plywood is nailed over the glued scarf joint with the nails extending into a supporting structure beneath
the skin. The strip is installed over vinyl sheeting to prevent it sticking to the skin. When the glue is
thoroughly dry, the nailing strip is broken away and the nails removed.
NAND gate (logic gate). A NOT AND logic gate having two or more inputs and one output. The output is
a logic zero (NOT one) if all of the inputs are logic one. The symbol for a NAND gate is the same as for an
AND gate, followed by a small circle to show that the output is inverted. (Its logic condition is changed.)
nano. The metric prefix meaning one billionth (1 x 10-9) of a unit.
nanovoltmeter. An extremely sensitive voltmeter that can measure voltages as low as one nanovolt (one
thousandth of a microvolt).
nap (fabric). The ends of the fibers in a fabric. Certain steps in the finishing of fabric materials cause the
nap to stick up. This is called “raising the nap.” When an aircraft structure is covered with cotton or linen
fabric, the first coat of dope raises the nap. This nap must be carefully removed by sanding to get a smooth
finish.
naphtha (aliphatic naphtha). A petroleum product whose boiling point is between that of gasoline and
kerosine. Aliphatic naphtha is used as a cleaning solvent and as an ingredient in certain finishing materials.
naphtha (aromatic naphtha). A solvent produced from coal tar. Aromatic naphtha is used as a blending
agent for changing the performance characteristics of gasoline. It has a softening effect on rubber goods,
such as flexible hoses and diaphragms used in pumps and fuel metering components.
narrowing grinding (reciprocating engine valve seat grinding). The grinding away of part of the top
edge of the valve seat in the cylinder of a reciprocating engine. Narrowing decreases the contact area
between the valve face and the valve seat.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 397
NASA. National Aeronautics and Space Administration. See NACA.
NAS specifications (National Aircraft Standards). Specifications established by the National Aircraft
Standards Committee for the design and construction of components. Parts conforming to these standards
are identified with a number preceded by the initials NAS.
NAS (national airspace system). The common network of U.S. airspace; air navigation facilities,
equipment and services, airports or landing areas; aeronautical charts, information and services; rules,
regulations and procedures, technical information, and manpower and material.
Included are system components shared jointly with the military.
NAS stage A (air traffic control). The enroute ATC system’s radar, computers and computer programs,
controller plan view displays (PVDs/radar scopes), input/output devices, and the related communications
equipment which are integrated to form the heart of the automated IFR air traffic control system.
This equipment performs flight data processing (FDP) and radar data processing (RDP). It
interfaces with automated terminal systems and is used in the control of enroute IFR aircraft.
National Flight Data Center. See NFDC.
National Flight Data Digest (air traffic control publication). A daily (except weekends and Federal
holidays) publication of flight information appropriate to aeronautical charts, aeronautical publications,
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航空术语词典Dictionary of Aeronautical Terms 中(141)
