the Aviation Dictionary

Doppler radar downlock pin
decompressed (lowered in frequency) when moving
apart.
used on the inside of the fuselage to strengthen the skin
where an antenna is attached.
Doppler radar -A radar system that indicates speed by doubler plies - In composites, a patch that extends over
measuring the amount of Doppler shift and equating it the sanded out area to the existing structure which
to the speed that the measured object is moving toward strengthens the repair. A doubler can also be used
or away from the measuring point.
where fasteners are used or where there are abrupt load
dorsal - Situated near the rear or on the back of an
transfers.
object. double-row radial engine -A radial engine having two
rows of cylinders and using two master rods attached to
dorsal fin - A fixed vertical control surface on the upper
a single crankshaft having two throws.
surface of an aircraft. Usually on the rear of an aircraft
and tapering into the vertical stabilizer, it increases the double-sided tape - Tape with adhesive on both sides.
directional stability of the aircraft.
double-tapered wing - A wing where both the chord
double flare - On rigid fluid
and theihickness ratio vary along the span.
lines, a connccti& flare
double-throw switch - A switch that selects one circuit
where the tubing is bent
from two possible circuits. Can have a center "off'
back on itself creating a
position.
double thickness. Only allowed
on soft materials in
dovetail - A method of joining two materials where one
small diameters.
has a base shaped like a widened, inverted, triangle that
fits into a similarly shaped cutout in the a&oining
double magneto - A single magneto housing that holds
piece. Often found in attaching turbine and compressor
one rotating permanent magnet and one cam with two
blades to rotor disks.
sets of breaker points, two condensers, two coils, and
two distributors. For all practical purposes, this dovetail fit - A shape similar to a cabinet maker's
constitutes two ignition systems. Also called a dual interlocking "dovetail joint." Primarily used to fit
magneto.
compressor blades into a compressor disk.
doublc spread - -The spreading of an adhesive equally
divided between the two surfaces to be joined.
double-acting actuator - An actuator that uses
hydraulic or pneumatic power to move the piston in
both directions.
double-acting hand pump - A hydraulic hand pump
that moves fluid with both the forward and rearward
movement of the handle.
double-backed tape - Adhesive tape that is sticky on
both sides.
double-cut file - A file with two sets of parallel
grooves, cut at an angle to each other.
double-cut saw - A saw with teeth shaped so that it cuts
in both the down and return strokes.
Dow 19 treatment - An acid treatment for magnesium
alloy parts, which produces an oxide film that inhibits
the formation of harmful corrosion.
Dow metal - A series of magnesium alloys produced by
the Dow Chemical Corporation.
dowel - A short wood or metal rod used to hold objects
together.
downburst - A strong downdraft which induces an
outburst of damaging winds on or near the ground.
Damaging winds, either straight or curved, are highly
divergent. The sizes of downbursts vary from 112 mile
or less to more than 10 miles. An intense downburst
often causes widespread damage. Damaging winds,
lasting 5 to 30 minutes, could reach speeds as high as
120 knots.
double-loop rib-stitching - Attachment of fabric to the downdraft - Any downward flow of air, for example,
aircraft structure using a double loop of rib-stitch cord the flow downwind of buildings or hills, or the sinking
at each stilch. air near thunderslorms especially in areas or
double-pole, double-throw (DPDT) switch - A switch
precipitation.
that controls two circuits, selecting either of two downdraft carburetor - A carburetor mounted on top
positions (and sometimes a third, off position) for each of the engine in which the flow of air into the engine is
circuit.
downward through the venturi.
double-pole, single-throw (DPST) switch - A switch
that controls two circuits, selecting either off or on.
doubler - In aircraft sheet metal, a thickness of metal
attached to the skin of an aircraft to strengthen it. Often
Aircraft Technical Book Company
P.O. Box 270
Tabernash, CO 80478
http:llw.ACTechbooks.com
downlock pin - A landing gear safety device consisting
of a pin that, when placed into a hole in the landing
gear apparatus, prevents the gear from retracting or
collapsing while on the ground. The downlock pin
must be removed before flight.