the Aviation Dictionary

H hand sni~s
hacksaw - A hand-operated metal cutting saw with
narrow, replaceable blades. The replaceable blade is
held in the hacksaw frame under tension.
hailstones - Precipitation formed by drops of water
carried by upward currents of wind inside a
cumulonimbus cloud to a level where the temperature
is low enough to freeze the drops into ice. When the
hailstones are too heavy to be carried in the cloud, they
fall to the ground.
hairline - A very thin line.
hairline crack - A nearly imperceptible crack on the
surface of a piece of material.
hairspring - A flat, coiled spring used in aircraft
instruments as either a calibrated restraint or a
preloading device for the gears.
halation - A distortion on a cathode-ray tube that shows
up as a blurred area around an image.
half hitch -A
knot used for lacing wire bundles.
half life - One half-life is the measure of the time a
particular radioactive material loses one half of its
radioactivity. At each half-life interval, the material
loses one half more of its remaining life and so on.
half view - An aircraft drawing that shows only one-half
of a symmetrical view. Center lines and break lines are
used to show that there is more of the object than is
shown in the drawing.
half-duplex communication - Communication in
which signals can be sent in one direction at a time, but
cannot be sent in both directions at the same time.
half-life inspection - A jet engine inspection required
under conditions of warranty, completed at half the
time between overhaul (TBO) interval. It includes
primarily a hot section disassembly, inspection, and
repair as necessary.
half-round file - A hand file that is flat on one side and
curved on the other.
half-section - A view in which the cutting plane extends
only halfway across the object, leaving the other half of
the object as an exterior view.
half-wave radio antenna - An antenna with an
electrical length that is approximately one half of the
wavelength of the frequency for which the antenna is
tuned.
half-wave rectifier - A rectifier that changes AC into
pulsating DC using one diode and producing only one
half of the AC wave in its output.
Hall-effect generator - An electronic device used to
measure the intensity of a magnetic field. Converts
magnetic field to a low-level electrical signal.
halo - A circle of light that appears around the moon
when seen through a thin layer of cirrostratus clouds.
The halo appearance is caused by tiny ice crystals in
the cloud that scatter the light passing through it.
halogen - One of the five chemical elements (fluorine,
chlorine, bromine, iodine, and astatine) in Group VII of
the periodic table of chemical elements. Used in some
fire extinguishing systems.
Halon - Low-toxicity, chemically stable compounds
used in fire protection systems. In aviation, Halon 1301
is most commonly used. The benefit of using Halon
fire extinguishers is that they do not leave liquid or
solid residues when discharged; therefore, they are
preferred for sensitive areas and can be used in the
presence of humans, which is important in closed
areas. Halons are being phased out since they are a
chlorofluorocarbon (CFC) and damage the ozone layer.
hammer - A hand-tool consisting of a heavy head and a
handle. It is used for pounding, driving, or shaping.
hammer welding - A forge welding in which the edges
of two pieces of metal are heated red-hot and then
fused by beating with a hammer.
hand drill - A hand-operated, eggbeater-type tool used
to turn a twist drill.
hand driving - A method of forming rivets in which the
head is driven with a hand set and hammer, and the
shank is bucked with a bucking bar.
hand file - A hand-operated cutting tool made of
high-carbon steel and fitted with rows of very shallow
teeth extending diagonally across the width of the tool.
hand forming - The process of shrinking, stretching, or
forming sheet metal by using soft-faced mallets or
hammers to force the metal down against suitable
forming blocks or into dies.
hand inertia starter - An inertia starter for
reciprocating engines in which the flywheel is brought
up to speed by a hand-operated crank.
hand lay-up - In composites, assembling layers of
reinforcement by hand. This includes the working the
resin into the fabric, as well as using a pre-preg fabric.
hand pump -A
of fluid.
pump operated by hand to create a flow
hand rivet set - A rivet set that can be clamped into a
vise to hold the manufactured head of the rivet while
the shank is upset with a hammer and a flat punch.
hand snips - Compound-action hand shears used for
cutting sheet metal. They normally come in sets of
Aircraft Technical Book Company
P.O. Box 270
Tabernash, CO 80478
http:llw.ACTechbooks.com