the Aviation Dictionary

drill . drop tank
altitude limits, it is incapablc of maintaining altitudc
with one engine inoperative, and the airplane will drift
down to the engine-out absolute ceiling.
drill - I. A rotary cutting tool drivcn with a drill motor
or a drill press. 2. To sink a hole with a drill, usually a
twist drill. 3. A pointed, rotating cutting tool.
drill bushing - Hardened steel sleeves inserted in jigs,
fixtures, or templates to provide a guide for drills so
holes will be straight and in the proper location.
drill chuck - The clamp on the spindle of a drill motor
or drill press into which the drill bit is fastened.
drill jig - A device that holds parts or units in the proper
position while holes are being drilled.
drill press - A power-driven drilling device that
includes a table for holding the material, a chuck for
holding the drill bit, a motor for driving the chuck, and
a means of feeding the drill into the material.
drill rod - A high carbon tool steel. It has a combination
of hardness and toughness for good wear
characteristics.
drilling burrs - Sharp ragged particles of metal left by
the drill when a hole is made.
drip pan - A shallow pan placed beneath an engine to
catch dripping fluids.
drip valve - A spring-opened and burner
pressure-closed mechanical valve located in the lower
portion of the combustor outer case, installed to drain
off puddled fuel after an aborted start or after
shutdown. Also referred to as a drain valve.
gauge - A stick used as a means of
checking the fuel level from beneath the wing of a
large jet transport aircraft. The stick is released and
pulled downward until fuel drips from its end,
signifying that the inside is even with the top of the
fuel in the tank. The fuel quantity is read where the
drip-stick enters the wing.
drive coupling - A coupling between the accessory
section of an engine and the component that is driven.
It is used to absorb torsional shock or to serve as a
safety link that will shear in case the component seizes.
drive fit - A fit between mating parts in which the part
to be inserted into the hole is larger - than the hole and
therefore must be driven or forced together with the
other part. Also referred to as an interference fit.
drive gear - In a gear train, the gear nearest the power
source. Meshes with and drives (turns) the driven gear.
drive screws - Plain-headed, self-tapping screws used
for attaching name plates to castings or to plug holes in
tubular structures through which rust-preventative oil
has been forced.
driven gear - In a gear train, the gear being driven
(turned) by the drive gear.
driver - In electronics, a device that supplies input
powcr to an output dcvicc.
driver head - A head on a bolt or screw designed for
driving the fastener by means of a tool such as a
screwdriver or Allen wench rather than a conventional
wrench.
drizzle - A form of precipitation. Very small water
drops that appear to float with the air currents while
falling in an irregular path (unlike rain, which falls in a
comparatively straight path, and unlike fog droplets
which remain suspended in the air).
drogue - A device that provides drag to a moving body.
For boats, a sea anchor provides drag that stabilizes the
position of the boat in relation to current. In aircraft a
drogue chute stabilizes or slows the airplane. A drogue
receptacle for refueling is a basket-shaped device into
which another aircraft can insert a probe to receive fuel
from an aerial refueling tanker.
drone - An unmanned aircraft guided by remote control.
Newest terminology refers to these vehicles as UAVs
(Unmanned Aerial Vehicles) and RPVs (Remote
Piloted Vehicles).
droop - Refers to the RPM loss that occurs when a fuel
control flyweight governor speeder spring is extended
and weakened. It takes less flyweight force to come to
equilibrium with the weaker spring force and
consequently slightly less speed results. The inability
of the engine power to increase as the rotor pitch is
increased causes the rotor to slow down.
droop compensator - In helicopters, a device that
automatically adds power when collective pitch is
increased in order to compensate for the increased load
placed on the engine.
droop restraint - A device used to limit the droop of
the main rotor blades at low RPM.
drop cloth - A plastic or fabric sheet used to protect
floors, furniture, or other objects from paint drips or
overspray from painting operations.
drop forging - A process of forcing semi-molten metal
to flow into a mold or die under the pressure of
repeated hammer blows.
drop hammer -- A large, heavy, hammer-type,
metal-forming machine that uses sets of matched dies
to form compound curved sheet metal parts. The metal
is placed over the female die and the male die is
dropped into it, forcing the metal to conform to the
shape of the two dies.
drop tank - An externally mounted fuel tank designed
to be dropped in flight.
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