the Aviation Dictionary

impeller . increase speed to (speed)
circuit. Resistance in ohms is drawn as the horizontal
base of the triangle and reactance in ohms is drawn
vertically at 90 degrees to the resistance. Impedance in
ohms is the hypotenuse of the triangle. The angle
between it and horizontal is called the "phase angle."
impeller - A vaned disc that picks up and accelerates
the air outwardly to increase the pressure in a
supercharger for a reciprocating engine, or to provide
the pressurized air for a centrifugal-type turbine
engine.
impingement starting - A turbine engine starting
process requiring no engine mounted starter. Air from a
source separate from the engine to be started is directed
onto the iurbine wheel(s) to cause engine rotation for
starting and then the air source is removed.
implode - To burst inward. The reverse of explosion.
impregnate - In reinforcing plastics, to saturate the
reinforcement with a resin.
impulse - A change in momentum caused by a surge or
pulse of energy.
impulse coupling - A spring-loaded coupling between a
magneto and its drive gear that causes the magneto to
produce a hot and late spark for starting the engine.
When the engine is being turned over slowly, the
magnet is restrained by stops, and the spring is wound.
At the proper time for the starting spark to occur, the
spring is released and the magnet is spun, producing a
hot, late spark. When the engine starts, centrifugal
force holds the coupling engaged so that it acts as a
solid unit.
impulse turbine - A stator
vane and rotor blade arrangement
whereby the vanes
form convergent ducts and
the blades form straight
ducts. The rotor is then
turned by impulse as gases
impinge on the blades. A
design common to turbine
driven accessories such as air
starters.
impulse-reaction turbine - A stator vane and rotor
blade arrangement whereby the base area is an impulse
design and the tip is a reaction design. This design is
common to flight engines.
added to silicon or germanium to give them some
desired electrical characteristic.
in ground effect (IGE) hover - In rotorcraft, hovering
close to the surface (usually less than one rotor
diameter distance above the surface) under the
influence of ground effect.
in phase - A condition in an electrical circuit where the
voltage and current rise and fall together. In an AC
circuit, the two pass through 0" and 180" at the same
time, going in the same direction.
inactive aircraft - An aircraft that is no longer
operational.
inboard - Toward the center of the aircraft.
incandescent - Glowing because of intense heat.
incandescent lamp - An electric lamp that produces
light by a white hot filament enclosed in a glass bulb
from which the air has been removed and replaced with
an inert gas.
incerfa (uncertainty phase) [ICAO]- A situation
wherein uncertainty exists as to the safety of an aircraft
and its occupants.
inches of mercury (in. Hg) - A measurement of air
pressure., normally used for atmospheric pressures. I
in. Hg. is equal to approximately
-.
If2 PSI.
inches per second (ips)--A
in electronic balancing.
velocity measurement. Used
incidence board - A device used to measure the angle
of incidence of a wing.
incipient stage - The time when frontal cyclone
development begins, pressure falls at some point along
the original stationary front and counterclockwise
circulation is generated.
inclined plane - A machine used to gain a mechanical
advantage. It consists of a flat surface positioned at an
angle with the horizon.
inclinometer - An instrument consisting of a curved
glass tube, housing a glass ball, and damped with a
fluid similar to kerosene. It may be used to indicate
inclination, as a level, or, as used in the turn and slip
indicator, to show the relationship between gravity and
centrifugal force in a turn.
inclusions - The impurities contained in a material.
impulsive - A learning style where a student makes a incompressible fluids -Any liquid such as oil or water.
quick assessment and then decides to take action. Liquids cannot be compressed but can be used in a
Impulsive students may not read each question or all of regulated fluid power system such as a hydraulic
the answer choices entirely. As a result, they tend to system to gain a mechanical advantage.
select the first choice that appears correct.
Inconel - A chromium-iron alloy similar to stainless
impurities - 1. Undesired foreign objects in a fluid. 2. A steel, but which cannot be hardened by heat treatment.
chemical element such as arsenic or phosphorus that is
increase speed to (speed)- See speed adjustment.
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