the Aviation Dictionary

downlocks - Mechanical locks that hold a retractable
landing gear in the "on" or "down" position, preventing
its retracting when the hydraulic pressure is released.
downslope wind - Wind moving down a slope, the wind
can be either a cold downslope wind or a warm
downslope wind.
downtime - The time an airplane is out of commission.
downwash - 1. Air deflected perpendicular to the
motion of the airfoil. 2. Air that has been accelerated
downward by the action of the main rotor of a
helicovter.
downlocks . driftdown
drag wire - A diagonal, load-carrying member of a Pratt
truss wing. It runs from the front spar inboard to the
rear spar outboard and carries tensile loads that tend to
drag back on the wing.
dragging brakes - Brakes that have not fully released
and that maintain some friction as the wheel rolls.
Dragging brakes cause serious overheating.
drain - The electrode in a field effect transistor (FET)
that corresponds to a collector of the ordinary
transistor.
drain can - A container to catch fuel drained from the
main fuel manifold after shutdown of a turbine engine.
downwash angle - The
angle the air is deflected
drain hole - A hole placed in the lower surface of a
downward by an airfoil.
wing or other sealed component to provide ventilation
It is the difference and allow the drainage - of anv accumulated moisture
between the angle of air approaching the airfoil and the
drain plug - A removable plug located at the lowest
air leaving it.
point of a system used for drainage purposes.
downwind - The direction in which the wind is
drain valve - A
blowing.
spring-opened and burner
pressure-closed mechanical valve located in the lower
downwind landing - Landing in a direction so that the portion of the combustor outer case, installed to drain
wind is coming - from behind the aircraft.
off puddled fuel after an aborted start or after
shutdown. Also referred to as a drip valve.
downwind leg - A flight path parallel to the landing
runway in the direction opposite to landing. The drainage wind -A shallow, small scale current of cold
downwind leg normally extends between the crosswind dense air accelerated down a slope by gravity.
leg and the base leg.
drape - In composites, the ability of a fabric or pre-preg
draftsman -A person who makes mechanical drawings. to conform to a contoured surface.
drag - An aerodynamic force on a body acting parallel
and opposite to the relative wind. The resistance of the
atmosphere to the relative motion of an aircraft. Drag
opposes thrust and limits the speed of the airplane.
drag brace - 1. In main landing gears, a device that acts
as side support for shock strut. 2. An adjustable brace
used to position the main rotor in a fixed position
preventing movement of the blade at the attached point
on semi-rigid rotors.
drag chute - A relatively small parachute attached to
the rear of an aircraft. Drag chutes are deployed during
landing rolls to help slow an aircraft and sometimes in
flight to increase drag.
drag coefficient - One of the aerodynamic
characteristics of an airfoil section that illustrates the
increase in induced drag as the angle of attack is
increased.
drag demonstration - The demonstration of the effects
of drag on a multi-engine airplane from landing gear,
flaps, and windmilling propellers.
drag hinge - The hinge on a helicopter rotor blade
parallel to the axis of rotation of the blade. It allows the
blade to move back and forth on a horizontal plane,
minimizing the blade vibrations.
draw filing - A method of hand filing in which the file
is grasped with both hands and moved crosswise over
the work. Draw filing produces an exceptionally
smooth surface.
draw knife - A knife with handles on either end,
designed to be pulled (drawn) toward the user.
draw set - A riveting tool used to force sheets of metal
together before they are riveted.
drawing -A graphic method of conveying information.
drawing number - The number assigned to each
drawing in a set of drawings and located in the lower
right-hand comer of the title block. It identifies the
drawing and is usually associated with the part number
of the component or part depicted in the drawing.
drift angle - The horizontal angle between the
longitudinal axis of an aircraft and its path relative to
the ground.
drift magnet - A small permanent magnet in a fixedcoil
ratiometer indicator. Used to drift or pull the
pointer off scale when the instrument is not energized.
drift punch -A pin punch with a long straight shank.
driftdown - The unavoidable descent due to the loss of
an engine when above the engine-out absolute ceiling
of an airplane. If the airplane is above its engine-out
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