the Aviation Dictionary

scavenger pump . sea lane
scavenger pump - A constant displacement pump in an
engine that picks up oil after it has passed through the
engine and returns it to the oil reservoir.
scheduled maintenance - The inspection and
replacement of components that are planned in advance
on a day, month, or operating hour basis.
schematic diagram - A graphical presentation used to
explain the operation of a system without showing its
mechanical details or physical layout. Also referred to
as a schematic drawing.
schematic drawing - A graphical presentation or
diagram used to explain the operation of a system
without showing its mechanical details or physical
layout. Also referred to as a schematic diagram.
scientific notation - In mathematics, a form of
shorthand. Numbers are displayed by using powers of
ten to indicate very large or very small numbers. For
example, 4,000,000 would be written as 4 X lo6 and
0.000004 would be written as 4 X
Scintilla magneto - A Swiss-designed and built
magneto. It is the forerunner of the current Bendix
magneto.
scoop - An air inlet that projects beyond the immediate
surface of an aircraft structure.
scope - 1. A contraction of oscilloscope. 2. Extent and
detail of an inspection or repair.
score - A deep scratch mark or line made across a piece
of material making it possible to break the material
along the line.
scoring - Deep scratches on the surface of a material
caused by foreign particles between moving parts.
scraper ring - The bottom ring on a piston whose
function is to scrape the lubricating oil away from the
cylinder wall. This prevents oil from getting into the
combustion chamber of the cylinder.
scratching surface - Narrow, sharp, shallow markings
or lines resulting from the movement of a particle or
sharp pointed object across a surface. The most
common cause is carelessness in handling and any part
can be so affected. Note: To distinguish it from
scoring, scratching is not considered to be caused by
engine operation.
screech liner - A perforated liner within an afterburner,
designed to combat destructive vibrations that cause
metal fatigue and noise emissions.
screeching - A shrill, high-pitch noise that comes from
a gas turbine engine caused by the instability of
combustion in the engine.
screeding tool - A tool used to smooth out or level
plastic resins used in bonded structure manufacturing
or repair.
screen - A frame covered with a netting or mesh
material used to cover an opening to prevent the entry
of foreign objects.
screen grid - The electrode in a four-element vacuum
tube used to minimize the interelectrode capacitance
between the plate and the control grid.
screen-type frlter - A fluid filter with an element that
consists of a wire screen.
screw dowel - A dowel pin provided with a straight or
tapered thread for threading into a material.
screw pitch gauge - A gauge with a series of V-notches
cut along one edge. Used to check the number of
threads, or pitch, of a screw or bolt.
screwdriver - A hand tool used for turning screws.
scriber - A hardened steel or carbide-tipped, pointed
tool used to scratch lines on metal for cutting.
scribing - The process of marking a line on metal with
the use of a scriber.
scroll combustor - Used widely on auxiliary power
units in conjunction with a radial inflow turbine, a
scroll combustor fits around the turbine nozzle that has
vane openings at its inner perimeter. The vanes direct
the gases inward onto the turbine.
scroll shear - A floor- or bench-mounted sheet metal
cutting tool used to cut irregular lines in a piece of
sheet metal without having to cut to the edge of the
sheet.
scud - Small patches of low clouds that usually form
below heavier overcast clouds.
scuffing surface - A dulling or moderate wear of a
surface resulting from a slight amount of rubbing.
Usually caused by improper clearance and insufficient
lubrication. Parts affected are rollers, rings, and steel
parts bolted together.
scupper - A recess around the filler neck of a he1 tank.
It collects any fuel spilled during the fueling operation
and drains it overboard rather than allowing it to enter
the aircraft structure.
sea anchor - An apparatus towed in the water to retard a
ship's drift and to keep the vessel facing into the wind.
sea breeze - A coastal breeze blowing from sea to land.
It occurs in the daytime when the land surface is
warmer than the sea surface.
sea breeze front - The boundary between the cool,
inflowing marine air in the sea breeze and the warmer
air over land.
sea lane - A designated portion of water outlined by
visual surface markers for and intended to be used by
aircraft designed to operate on water.
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