the Aviation Dictionary

horizon . hot streak ignition
horizon - The line of sight boundary between the Earth
and the sky.
horizontal - Parallel to the Earth's horizon or to the base
line of an object.
horizontal needle of the cross-point indicator - The
glide slope indicator of the standard ILS indicator
(cross point indicator). The horizontal bar is also
referred to the horizontal needle and indicates the
position of the aircraft on the ILS glideslope.
horizontal pressure gradient force - The force that
arises because of a horizontal pressure gradient.
horizontal stabilizer - A fixed horizontal airfoil
attached to the rear of the fuselage to provide stability
in pitch.
horizontal wind shear - The change in wind direction
andfor speed over a horizontal distance.
horizontally opposed engine - A reciprocating engine
with the cylinders arranged in two horizontal rows, one
on either side of the crankshaft. The cylinders are
slightly staggered, with the cylinders in one bank
slightly ahead of those in the other bank. Staggering
the cylinders allows each piston to be connected to a
separate throw of the crankshaft.
horn - A lever or device fastened or connected to a
control surface to which an operating cable or rod is
attached.
horse latitudes - Approximately 30" to 35O north and
south latitudes. An area of high barometric pressure
and light, changeable winds.
horsepower (HP)- The standard unit of power used for
mechanical measurement. It is equal to 33,000 ft.-lbs.
of work done in one minute, or 550 ft.-lbs. of work
done in one second. Electrically, it is equal to 746
watts.
horseshoe magnet - A magnet shaped like the letter
"U"(or a horseshoe).
hose - A flexible plumbing line used in place of rigid
tubing in areas subiect to movement or vibration.
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hose clamp - A metal clamp used to hold a rubber hose
onto a piece of rigid tubing.
hot air muff - A jacket installed around a tail pipe. Air
routed through the hot air muff picks up heat by
convection through the tail pipe material. This heated
air is then routed to the cabin.
hot bond repair - In composites, a repair made using a
hot patch bonding machine to cure and monitor the
curing operation.- Hot bonding equipment typically
includes both the heat source and the vacuum source.
hot corrosion - Corrosion occurring in hot sections
from a chemical reaction between sulfur in the fuel and
salt in the air stream. This condition is more of a
problem when operating near salt water.
hot dimpling - A coin dimpling or countersinking of
metal for flush-rivets or screws. A heating unit heats
the metals to prevent cracking around the hole.
hot forming - Working operations such as bending and
drawing sheet and plate, forging, pressing, and
heading, performed on metal heated to temperatures
above room temperature.
hot junction - One end of a thermocouple. When
combined with a cold junction, a small current is
generated. The same principle is used in many fire
detection systems. The cold junction is sometimes
referred to as the reference junction.
hot section - The portion of a turbine engine aft of the
diffuser where combustion takes place.
hot section distress - Any of the metal deterioration
conditions found in the hot section such as warping or
creeping.
hot section inspection - An inspection of the hot
section of a gas turbine engine.
hot shearing - A method of cutting heavy sheets of
magnesium alloys in which the metal is cut while hot.
This improves the smoothness of the cut.
hot spark plug - A spark plug with a long-nose
insulator in which the heat transferring from the center
electrode into the shell has a long path to travel. Hot
spark plugs are used in engines that operate relatively
cool, and they keep the center insulator hot enough to
prevent the accumulation of lead oxides.
hot sparks - Localized areas in the cylinder of an
internal combustion engine that are overheated to the
point where they become incandescent or glow. They
cause pre-ignition.
hot spots - Localized discoloration on hot section parts
indicating a breakdown of cooling air or harmful
concentition of fuel at that point.'~his often is the
result of a malfunctioning fuel nozzle.
hot stamping - A method of identifying or imprinting
plastic materials, cloth, or paper by using heated metal
dies.
hot start - In gas turbine engines, a start which occurs
with normal engine rotation, but exhaust temperature
exceeds prescribed limits. This is usually caused by an
excessively rich mixture in the combustor. The fuel to
the engine must be terminated immediately to prevent
engine damage.
hot streak ignition - An afterburner ignition system in
which a stream of raw fuel continues to bum while
passing through the turbine section and provides
ignition for afterburner fuel supply.
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