the Aviation Dictionary

Fowler flap - frequency modulation (FM)
inward stroke of the piston with both valves closed,
and finally, the exhaust stroke occurs when the piston
moves outward with the exhaust valve open. At this
point, the cycle begins again.
Fowler flap - Wing flaps that are lowered by sliding
from the trailing edge of the wing on a track. Fowler
flaps modify the shape of the airfoil and increase the
area of the wing.
fractional distillation - A process of oil refining in
which the crude oil is heated to the boiling point. As
each type of hydrocarbon rises through the distillation
column, the heavier components begin to cool and
condense into liquids. Liphter - fractions such as
propane and butane continue to rise and condense later.
As a result, different fractions are separated by a
process of condensing, or distilling, at different
temperatures.
fractions - The various components of a hydrocarbon
fuel separated by the distillation process.
frame - A former ring that provides shape and rigidity
to a semi-monocoque or monocoque structure.
free balloon - A lighter-than-air, helium-filled device
used in weather observations to find the height of the
base of the lower layer of clouds.
free electrons - Those electrons so loosely bound in the
outer shells of some atoms that they are able to move
from atom to atom when an electro motive force is
applied to the material.
free fit - A loose fit between moving parts such as a nut
that turns easily on the threads of a screw or bolt.
free power turbine - In gas turbine engines, a turbine
wheel which drives a power output gearbox rather than
a compressor. Found in Turboprop and Turboshaft
engines.
free turbine - A turboshaft engine with no physical
connection between the compressor and power output
shaft.
free water Liquid water that has condensed out and is
no longer - entrained in a turbine engine - fuel.
free-air wire -A wire completely open to air circulation
and not in a bundle.
free-running multivibrator - An oscillator that
alternates between two different output voltage levels
during - the time it is on. The output remains at each
voltage level for a definite period of time. Produces a
continuous square or rectangular waveform. The freerunning
multivibrator has two outputs, but no inputs.
Also referred to as an astable multivibrator.
freeze - 1. The process in which a liquid changes into a
solid due to the removal of heat energy. 2. The
stoppage of a mechanical device due to binding of the
mechanical mechanism.
freeze calculated landing time - A dynamic parameter
number of minutes prior to the meter fix calculated
time of arrival for each aircraft when the TCLT is
frozen and becomes an ACLT (i.e., the VTA is updated
and consequently the TCLT is modified as appropriate
until FCLT minutes prior to meter fix calculated time
of arrival, at which time updating is suspended and an
ACLT and a frozen meter fix crossing time (MFT) is
assigned).
freeze speed parameter - A specd adapted for each
aircraft to determine fast and slow aircraft. Fast aircraft
freeze on parameter FCLT and slow aircraft freeze on
parameter MLDI.
freezelfrozen - Terms used in referring to arrivals
which have been assigned ACLT's and to the lists in
which they are displayed.
freezing - Change of state from liquid to solid.
freezing drizzle - Drizzle that freezes on contact.
freezing level - A level in the atmosphere at which the
temperature is 32" F (0" C).
freezing level chart - A chart depiction of the freezing
levels, reported in hundreds of feet.
freezing point - The temperature at which a liquid will
change into a solid.
freezing - rain - Rain that lreezes upon contact with the
ground or other objects, such as trees, power lines and
aircraft.
French fell seam - A type of machine-sewn seam.
Recommended for sewing together sheets of aircraft
fabric.
Freon - A fluorinated hydrocarbon compound used as a
fire extinguishing agent or a refrigerant for vapor-cycle
air conditioning systems. A registered trademark of E.1.
DuPont de Nemours & Company.
frequency - The number of waves that pass some fixed
point in a given time interval, measured in cycles per
second (cps) or Hertz (Hz).
frequency converter - A circuit device that changes the
frequency of an alternating current.
frequency meter - An electronic instrument that
measures and indicates the frequency - - of an alternating -
current on a dial or digital display.
frequency modulation (FM) - A radio wave
~,
transmission method where information is transmitted
freewheeling unit - In rotorcraft, a component of the
transmission or power train that automatically by varying the modulation signal in proportion to the
disconnects the main rotor from the engine when the audio signal.
engine stops or slows below the equivalent rotor r.p.m.
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