mass. The amount of matter, or material, in an object. To find the mass of an object, divide its weight, in pounds, by 32.2. The constant, 32.2, is derived from the fact that a freely falling object is accelerated by the force of gravity 32.2 feet per second each second it falls.
Mass = Weight / 32.2
mass flow rate. The product of fluid density and its linear velocity. The symbol for mass flow rate is the letter G.
massive-electrode spark plug. A type of spark plug used in aircraft reciprocating engines. A massive-electrode spark plug has three or four nickel-alloy ground electrodes surrounding the insulated center electrode.
Massive-electrode spark plugs provide reliable ignition under normal operating conditions, but are replaced with fine-wire spark plugs in conditions where lead fouling is a problem.
mass production. A method of producing large numbers of identical objects by the use of specialized jigs and fixtures. In the process of mass production, the manufacturing procedure is broken down into small steps that can be performed by automatic machinery or that can be done quickly and repeatedly by unskilled workers. Mass production of interchangeable parts has made the manufacture of complex equipment possible and economical.
master cylinder (hydraulic brake system component). The cylinder in an aircraft hydraulic brake system whose piston is moved by the pilot. When the piston is pressed into the master cylinder, hydraulic fluid is forced into the wheel cylinder, applying the brake.
master rod (radial reciprocating engine component). The only rod in a radial engine that connects a piston directly to the crankshaft. The crankshaft of a radial engine has only one throw for each row of cylinders, and the large end of the master rod rides on the journal of this throw. The small end of the master rod is connected through a wrist pin to one piston. The pistons in all the other cylinders in that row attach to link rods (articulated rods) that connect to the master rod through knuckle pins.
master switch (aircraft electrical system). A single switch that controls electrical power to all the circuits in an aircraft electrical system. When the master switch (a form of safety switch) is off, no circuit can be energized.
mat (reinforced plastic component). A pack of loose glass fibers that can be impregnated with a plastic resin to strengthen parts being formed in a mold.
matching transformer (electrical component). An electrical transformer with a turns ratio between its coils that matches the impedance of the load to the impedance of the source of electrical power.
The impedance of the primary winding of the transformer is the same as the output impedance of the source, and the impedance of its secondary winding is the same as the impedance of the load. The maximum amount of power can be transferred in an electrical circuit when the impedance of the source matches the impedance of the load.
matrix (composite materials component). The material that bonds the fibers together and carries the stresses into the fibers in a piece of advanced composite structure. Resins are the most widely used matrix material.
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