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from it.
splayed patch (plywood patch). A type of patch made in an aircraft plywood structure in which the edges
of the patch are tapered for approximately five times the thickness of the plywood. A splayed patch is not
recommended for use on plywood less than 1/10-inch thick.
splice connector (electric wiring). A solderless, crimped-on connector used to join two wire ends. The
splice connector is made in the form of an insulated metal tube. The insulation is stripped from the ends of
the wires to be spliced, and the bare wire is slipped into the tube. The tube is then crimped onto the wire. A
solderless splice connector forms a joint that is physically as strong as the wire, and it has an extremely low
electrical resistance. See illustration for solderless connectors.
splice knot (aircraft covering material). A special knot used to join two pieces of waxed rib-stitching
cord. A splice knot is superior to a square knot because it will not slip.
splined propeller shaft (reciprocating engine component). A propeller shaft with splines along its
periphery that fit into mating splines in the steel propeller hub. A splined propeller shaft is indexed to the
hub by a master spline which allows the propeller to be installed with only one orientation to the engine
crankshaft.
splines. A method of locking a shaft into a wheel or disk. A number of equally spaced parallel slots are cut
lengthwise into the surface of a shaft. Matching slots are cut in the inside surface of the hole into which the
shaft fits, and the splines prevent the shaft rotating in the hole.
split (wood defect). A longitudinal crack in a piece of wood caused by externally induced stress.
split bus. A type of electrical bus that allows all of the voltage-sensitive avionic equipment to be isolated
from the rest of the aircraft electrical system when the engine is being started or when the ground-power
unit is connected.
split-field motor. A reversible DC electric motor that has two separate field windings; one for clockwise
rotation and the other for counterclockwise rotation.
split flaps (aircraft controls). A type of wing flaps in which a part of the under side of the wing or the
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 546
trailing edge of the wing splits and folds down to increase the curvature (camber) of the bottom of the wing.
The increased camber increases the drag and also the lift produced by the wing under low-speed flight
conditions.
split lock washer. A heavy spring-steel washer split at an angle across its face and twisted. When a nut is
tightened down over a split lock washer, the twist is flattened out, and the spring action of the washer
pushes against the nut and holds its threads tight against the threads of the bolt. This pressure between the
threads prevents vibration from loosening the nut.
split needles (helicopter instrument indication). The indication on a helicopter tachometer that shows the
rotor clutch is not fully engaged. A helicopter tachometer has two needles; one shows the speed of the
engine and the other, the speed of the main rotor. When the clutch is fully engaged and the rotor is coupled
to the engine, the needles are “married”—one is directly on top of the other.
When the engine is started and the rotor is coming up to speed, the engine RPM needle is ahead of
the rotor RPM needle. When the engine is throttled back, and the rotor freewheels, the rotor needle is ahead
of the engine needle. In either case, the needles are said to be split.
split-phase induction motor. A type of alternating current motor that has a main and an auxiliary winding
connected in parallel. The phase of the current flowing in the auxiliary, or start, winding is shifted from that
flowing in the main winding, either by a capacitor or by a large difference in the resistance in the two
windings. The phase difference between the current flowing in the two field windings produces a rotating
magnetic field which starts the rotor spinning.
When the rotor is spinning at a specified speed, a centrifugal switch opens the auxiliary-winding
circuit, and the motor operates with only the main winding.
split-rocker switch. An electrical switch whose operating control is a rocker, split so one half of the switch
can be opened without affecting the other half. Split-rocker switches are used as aircraft master switches.
The battery can be turned on without turning on the alternator, but the alternator cannot be turned on
without also turning on the battery. The alternator can be turned off without turning off the battery, but the
battery cannot be turned off without also turning off the alternator.
spoiler (aircraft control). A small deflector that can be raised into the air flowing over an airfoil. When a
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航空术语词典Dictionary of Aeronautical Terms 下(64)
