Aviation Maintenance Terms beginning with N
N1
A symbol representing the rotational speed of the low- pressure compressor in a dual-spool gas turbine engine.
N2
A symbol representing the rotational speed of the high- pressure compressor in a dual-spool gas turbine engine.
Nacelle
An enclosed compartment, normally in the leading edge of the wing, in which an aircraft engine is mounted.
Naphtha
A volatile, flammable liquid distilled from petroleum. It is used as a cleaning agent and solvent, and is present in some blended turbine-engine fuels.
Naturally aspirated engine
A reciprocating engine that depends upon atmospheric pressure to force the air/fuel mixture into the cylinders. Naturally aspirated engines are neither supercharged nor turbocharged.
Net thrust
The thrust produced by a turbojet or turbofan engine in which the acceleration factor is the difference between the velocity of the incoming air and the velocity of the exhaust gases leaving the engine.
Neutral position
The position of the magnet in a magneto when its poles are between the pole shoes and no lines of flux are flowing through the magnetic circuit.
Newton
The unit of force needed to accelerate a mass of one kilogram one meter per second per second. One newton is equal to 1000,000 dynes, or 2.248 × 10-1 pound.
Nichrome
The registered trade name for an alloy of nickel and chromium. Nichrome wire is used for making electrical heater elements and precision wire-wound resistors. Nichrome’s resistance is approximately 65 times that of copper.
Nitriding
A method of case hardening steel. Steel is placed in a retort (a sealed, high-temperature furnace and heated to a specified temperature while surrounded by ammonia gas (NH3). The ammonia breaks down into nitrogen and hydrogen, and the nitrogen unites with some of the alloying elements in the steel to form an extremely hard surface. Nitriding hardens crankshaft bearing surfaces and cylinder walls in reciprocating engines. It takes place at a lower temperature than other forms of case hardening, and does not cause warping.
Normal category airplane
An aircraft that is certificated under 14 CFR part 23 that is not certificated under the acrobatic, utility, or commuter category.
Normal shock wave
A type of pressure wave that forms at right angles to a surface when air moves at the speed of sound.
Notch sensitivity
A measure of the loss of strength of a material caused by the presence of a notch, or a V-shaped cut.
Nozzle guide vanes
See turbine inlet guide vanes.
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