the Aviation Dictionary

IRAN isotach
IRAN -An acronym used by the military services for a isobaric range - That range of cabin pressurization in
form of maintenance known as Inspect and Repair As which the cabin maintains a constant pressure, or cabin
Necessary.
altitude, as the flight
iridium - An extremely hard and brittle metallic
altitude changes.
element of the platinum group, with a symbol of Ir and isogonic lines - Lines on
an atomic number of 77. Used for electrodes of an aeronautical chart -
Fine-wire spark plugs that must operate in extreme connecting points of
lead-fouling conditions.
equal
declination (angle
iris exhaust nozzle - In turbine engines, a nozzle design
between magnetic
similar to a camera shutter. It can be a two-position,
North and true North). This angle is known as compass
partially-open/fully-open or a variable opening type.
variation.
The widest opening is for afterburner mode. The
variable opening type is controlled to continuously isogonic Lines - Lines on charts that connect points of
seek the optimum position for existing conditions.
equal magnetic variation.
Irish linen - A strong fabric made from flax used to
cover many of the older aircraft. It is still popular in
Europe, but it is no longer readily available in the
United States. It may be used as a direct replacement
for grade-A cotton.
iron - A heavy, malleable, ductile, magnetic,
silver-white metallic element with a symbol of Fe and
an atomic number of 26. It is used in the production of
steel and all ferrous metals.
iron-constantan thermocouple - A low temperature
thermocouple that operates up to about 800" C. Used in
aviation primarily to measure cylinder head
temperature.
iron-core coil - An inductor that consists of a soft
laminated iron core around which wire is wound.
iron-core transformer - An electrical transformer that
has coils wound around soft iron cores. The cores cut
down on eddy-current losses but limit the use of the
transformer to lower frequencies.
iron-vane movement - An AC electric measuring
instrument that depends upon a soft-iron vane or
movable core operating with a coil to produce an
indication of AC current flow.
irrelevant questions - A question that has no
relationship with the subject matter being tested.
Serves only to disrupt the orderly learning process.
irreversible controls - Hydraulically-controlled
surfaces on an aircrafi that do not provide aerodynamic
feedback to the cockpit controls.
isobar - A line on a meteorological chart that connects
points on the Earth's surface having equal barometric
pressure.
isobar -A
line of equal or constant barometric pressure.
isobaric metering valve - A metering valve in a cabin
pressurization system that maintains a constant cabin
altitude.
isoheight - A line that shows contours of equal height
on a constant-pressure weather chart.
isohumes -Lines
of equal relative humidity.
isolation mount - A rubber and metal composite used to
prevent vibration transfer from one component to
another.
isolation transformer - An electrical transformer with
equal numbers of turns in the primary and secondary
coils. This type transformer is used to isolate a piece of
equipment from its power source.
isolation valve - A valve in an aircraft pneumatic
system that can be shut off to isolate the components
from the source of air pressure so maintenance can be
performed without discharging the system.
isoline - A line on a weather chart showing contours of
equal values of some quantity. It could be equal height
(isoheight), barometric pressure (isobar), temperature
(isotherm), wind (isotach), etc.
isometric drawing - The representation of an object in
isometric projection in which the lines parallel to the
edges of the object are drawn to true length.
isometric projection - A three-dimensional projection
in which the three faces of an object are equally
inclined to the surface of the drawing, and all of the
edges are equally foreshortened.
iso-octane - A hydrocarbon (CsHls) that has a very high
critical pressure and temperature. It is used as a
reference for measuring the anti-detonation
characteristics of a fuel.
isopleth - A line connecting points of constant or equal
value.
isopropyl alcohol - Fluid that prevents the formation of
ice on the blades during flight. Used in anti-icing
systems for propeller blades.
isostatic forging - A similar process to isothermal
forging.
isotach -A
Aircraft Technical Book Company
P.O. Box 270
Tabernash, CO 80478
http://w.ACTechbooks.com
line of equal or constant wind speed.