Fractional distillation.  A method of separating the various  components from a physical mixture of liquids. The material  to be separated is put into a container and its temperature is  increased. The components having the lowest boiling points  boil off first and are condensed. Then, as the temperature is  further raised, other components are removed. Kerosene,  gasoline, and other petroleum products are obtained by  fractional distillation of crude oil. Fusible plugs.  Plugs in the wheels of high-performance  airplanes that use tubeless tires. The centers of the plugs are  filled with a metal that melts at a relatively low temperature. If a takeoff is aborted and the pilot uses the brakes excessively,  the heat transferred into the wheel will melt the center of the  fusible plugs and allow the air to escape from the tire before  it builds up enough pressure to cause an explosion. Frangible.  Breakable, or easily broken. Freon.  The registered trade name for a refrigerant used in a  vapor-cycle air conditioning system. Frise aileron.  An aileron with its hinge line set back from the  leading edge so that when it is deflected upward, part of the  leading edge projects below the wing and produces parasite  drag to help overcome adverse yaw. Full-bodied.  Not thinned. Fully articulated rotor.  A helicopter rotor whose blades are  attached to the hub in such a way that they are free to flap,  drag, and feather. See each of these terms. Frost.  Ice crystal deposits formed by sublimation when the  temperature and dew point are below freezing. Fuel-flow transmitter.  A device in the fuel line between the  engine-driven fuel pump and the carburetor that measures the  rate of flow of the fuel. It converts this flow rate into an electrical  signal and sends it to an indicator in the instrument panel. Fuel jettison system.  A system installed in most large  aircraft that allows the flight crew to jettison, or dump, fuel  to lower the gross weight of the aircraft to its allowable  landing weight. Boost pumps in the fuel tanks move the fuel  from the tank into a fuel manifold. From the fuel manifold,  it flows away from the aircraft through dump chutes is each  wing tip. The fuel jettison system must be so designed and  constructed that it is free from fire hazards. Fuel totalizer.  A fuel quantity indicator that gives the  total amount of fuel remaining on board the aircraft on one  instrument. The totalizer adds the quantities of fuel in all of  the tanks. Fungus (plural: fungi).  Any of several types of plant life  that include yeasts, molds, and mildew. GHz (gigahertz).  1,000,000,000 cycles per second. G-17 Gerotor pump.  A form of constant-displacement gear pump.  A gerotor pump uses an external-tooth spur gear that rides  inside of and drives an internal-tooth rotor gear. There is  one more tooth space inside the rotor than there are teeth  on the drive gear. As the gears rotate, the volume of the  space between two of the teeth on the inlet side of the pump  increases, while the volume of the space between the two  teeth on the opposite side of the pump decreases. Generator shunt field.  A set of field windings in a generator  connected in parallel with the armature. Varying the amount  of current flowing in the shunt field windings controls the  voltage output of the generator. Generator series field.  A set of heavy field windings in  a generator connected in a series with the armature. The  magnetic field produced by the series windings is used to  change the characteristics of the generator. Generator.  A mechanical device that transforms mechanical  energy into electrical energy by rotating a coil inside a  magnetic field. As the conductors in the coil cut across the  lines of magnetic flux, a voltage is generated that causes  current to flow. Gear-type pump.  A constant-displacement fluid pump that  contains two meshing large-tooth spur gears. Fluid is drawn  into the pump as the teeth separate and is carried around the  inside of the housing with teeth and is forced from the pump  when the teeth come together. Gasket.  A seal between two parts where there is no relative  motion. Galling.  Fretting or pulling out chunks of a surface by sliding  contact with another surface or body. Gauge pressure.  Pressure referenced from the existing  atmospheric pressure. Gauge (rivet).  The distance between rows of rivets in a  multirow seam. Gauge is also called transverse pitch.