flywheel. A heavy wheel used to smooth the pulsations in a drive system. A reciprocating engine delivers its power in a series of pushes as each cylinder, in turn, goes through its power stroke. A heavy flywheel stores kinetic energy from each power stroke and gives it back by keeping the engine turning between power strokes. An airplane engine does not need a flywheel, because the propeller serves the same purpose.
flywheel effect (electronic circuit). One of the characteristics of an LC circuit, a circuit that contains both inductance and capacitance. If a class-C amplifier supplies an LC circuit with short pulses of energy at the proper time, the magnetic field around the inductor will build up and decay, and the capacitor will charge and discharge.
The LC circuit acts as a flywheel, and a continuous flow of alternating current is maintained between the inductor and capacitor, even though the energy is supplied in short pulses. Energy stored in the electromagnetic and electrostatic fields is supplied to the circuit during the time it is not being supplied by the amplifier.
FM (radio modulation). See frequency modulation.
FMC (flight management computer). An electronic flight instrumentation system that allows the flight crew to initiate and implement a given flight plan and monitor its execution.
FMS (flight management systems) (air traffic control). A computer system that uses a large data base to allow routes to be preprogrammed and fed into the system by means of a data loader. The system is constantly updated with respect to position accuracy by reference to conventional navigation aids.
The sophisticated program and its associated data base insures that the most appropriate aids are automatically selected during the information update cycle.
foamed plastic. A synthetic resin filled with millions of tiny bubbles. Foamed plastic is lightweight and resilient (soft and pliable) and is used as a packing material and a thermal (heat) insulator. Foamed plastic is sometimes called expanded plastic.