the Aviation Dictionary

drop-forged part - A steel part that has been formed by
the drop-forging process.
droplets - Tiny drops of liquid.
- -
drop-out voltage - In electricity, the minimum voltage
that can be applied to a device without it dropping from
the circuit. Usually used in referring to relays that dew
energize when control voltage drops below a certain
drop-out voltage.
dropping resistor - A resistor used to decrease the
voltage in a circuit.
drum brake - A friction device used on some aircraft
landing gear. Consists of a cylindrical metal drum
attached to the wheel and shoe-shaped friction vads
attached to the landing gear. This device is applied
against the inner side of the drum when braking action
is desired.
dry adiabat - A line on a thermodynamic chart
representing a rate of temperature change at the dry
adiabatic lapse rate.
dry adiabatic lapse rate (DALR) - The rate of
decrease of temperature with height of unsaturated air
lifted adiabatically (not heat exchange). Numerically
the value is 3C or 5.4F per 1000'.
dry adiabatic process - The cooling of an unsaturated
parcel of air by . expansion . and the warming - of a parcel
of air by compression.
dry air - Air that contains no water vapor. Dry air
weighs 0.07651 pounds per cubic foot under standard
sea level atmospheric conditions of 59°F (15°C) and a
barometric Dressure of 14.69 PSI. or 29.92 inches of
mercury.
dry air pump - An engine-driven air pump using
carbon vanes and that does not require any lubricating
oil in the pump for sealing or cooling.
dry bulb - A name given to an ordinary thermometer
used to determine temperature of the air; also used as a
contraction for dry-bulb temperature. Compare wet
bulb.
dry clearance - Clearance adjusted in adjusting valve
tappets without any oil in the tappet body.
dry fiber - In composites, a condition in which fibers
are not fully encapsulated by resin during pultrusion.
dry ice - Frozen carbon dioxide (COz). Dry ice
sublimates from solid to gas without becoming a liquid.
It is used for non-mechanical cooling of perishables or
for cooling parts for an interference fit.
dry laminate - In composites, a laminate containing
insufficient resin for complete bonding of the
reinforcement.
drop-forged part. dual rotor system
dry line - The moisture boundary, where the moisture
content of the air changes rapidly from one side to the
other.
dry operation - The operation of an aircraft engine
equipped with a water injection system, but operating
without the benefit of water injection.
dry rot - The condition of wood attacked by hngus.
Causes brittleness and decay.
dry wash - Aircraft cleaning method in which cleaning
material is applied by spray, mop, or cloth and
removed by mopping or wiping with a clean, dry cloth.
It is used to remove airport film, dust, and small
amounts of dirt and soil.
dry-bulb temperature - The temperature of the air
without the effect of water evaporation.
dry-cell battery - Common name for a carbon-zinc,
single-cell battery. D-, C-, AA-, and AAA-cells are all
dry-cell batteries. They are not rechargeable or
serviceable.
dry-charge battery - The common way of shipping a
lead-acid battery. The battery is fully charged, drained,
and the cells are washed and dried. The battery is
sealed until it is ready to be put into service. Electrolyte
is added and the battery is given a freshening charge,
making it ready for service.
dry-chemical fire extinguisher - An extinguishing
agent such as sodium bicarbonate used as a
compressed, non-flammable gas as a propellant. Drychemical
fire extinguishers are usually rated for
multiple purpose use.
dry-sump engine - An engine in which most of the
lubricating oil is carried in an external tank and is fed
to the pressure pump by gravity. After it has lubricated
the engine, the oil is pumped back into the tank by an
engine-driven scavenger pump.
dry-sump system - An oil system in which the oil is
contained in a separate tank and circulated through the
engine by pumps.
dual controls - Two sets of flight controls for an aircrafi
that allow the airplane to be flown from either of two
positions.
dual indicator - An aircraft instrument that provides
two sets of indications on one dial. For example, the oil
pressure of both engines can be shown on one indicator
using one dial and two pointers.
dual magneto - A single magneto housing that holds
one rotating permanent magnet and one cam with two
sets of breaker points, two condensers, two coils, and
two distributors. For all practical purposes, this
constitutes two ignition systcrns.
dual rotor system - The rotor system of a helicopter in
which there are two separate main rotors spinning in
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