Aviation Maintenance Terms beginning with L
Labyrinth seal
A type of air and/or seal used around the main –shaft bearings in a gas turbine engine. The seal consists of a series of rotating blades that almost contact the seal land. A small amount of air flows between the seal and the land to prevent oil flowing past the seal.
Land (piston)
The portion of a piston between the ring grooves.
Land (splined shaft)
The portion of a splined shaft between the grooves.
Laser tachometer
A highly accurate tachometer that shines a laser beam on a rotating element that has reflective tape or a contrasting mark. The reflected laser beam is converted into electrical pulses which are counted and displayed on a monitoring instrument.
Last-chance oil filter
A small filter installed in the oil line to the bearing jet in a gas turbine engine. This filter traps any contaminants that have passed the main filter and holds them until the engine is disassembled for overhaul.
Leading edge
The thick edge at the front of a propeller blade.
Lean die-out
A condition in which the fire in a gas turbine engine goes out because the air/fuel mixture ratio is too lean to sustain combustion.
Lean mixture
A air/fuel mixture that contains more than 15 parts of air to 1 part of fuel, by weight.
Line boring
A method of assuring concentricity of bored holes. A boring bar extends through all of the holes and cuts the inside diameters so they all have the same center.
Link rod
The rod in a radial engine that connects one of the piston wrist pins to a knuckle pin on the master rod. Also called articulating rods.
Liquid cooling
The removal of unwanted heat from an aircraft engine by transferring the heat into a liquid and then passing the heated liquid through a liquid-to-air heat exchanger (radiator) to transfer the heat into the ambient air.
Longitudinal magnetism
A method of magnetizing through a solenoid, or coil, that encircles the part so the lines of magnetic flux pass lengthwise through the part. Longitudinal magnetism makes it possible to detect faults that extend across the part.
Low bypass ratio engine
A turbofan engine whose bypass ratio is less than 2:1.
Low unmetered fuel pressure
Pressure in a Teledyne- Continental fuel injector pump that is adjusted by the relief valve.
Low-pressure compressor
The first-stage compressor in a dual-spool gas turbine engine. The low-pressure compressor is called the N1 compressor and its speed is not governed. It seeks its own best speed as the atmospheric conditions change so it can furnish a relatively constant mass of air to the inlet of the second-stage compressor.
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