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stabilizer (airplane) - Any airfoil whose primary function is to increase the stability of an aircraft. It usually refers to the fixed horizontal tail surface of an airplane, as distinguished from the fixed vertical surface. (see fig. 5.)
stabilizer (aerostat) - Same is FIN.
stabilizer, stub-wing - A projection from the side of the central hull of a flying boat intended to increase the buoyancy and stability of a flying boat while the boat is at rest and to increase the hydrodynamic lift during the take-off. It is an integral part of the hull, and usually takes the form of a stumpy airfoil or a stub wing.
stagger - A term referring to the longitudinal position of the axes of two wings of an airplane. Stagger of any section is measured by the acute angle between a line joining the wing axes and a line perpendicular to the upper wing chord, both lines lying in a plane parallel to the plane of symmetry. The stagger is positive when the upper wing is in advance of the lower. (See fig. 5.)
stall - The condition of an airfoil or airplane in which it is still operating at an angle of attack greater than the angle of attack of maximum lift.
stalling speed - See SPEED, STALLING.
standard atmosphere - See ATMOSPHERE, STANDARD.
static ceiling - See CEILING, STATIC.
static pressure - The force per unit area exerted by a fluid on a surface at rest relative to the fluid. 
static stability - See STABILITY, STATIC.
static tube - A cylindrical tube with a closed end and a number of small openings normal to the axis, pointed upstream, used to measure static pressure. 
station, airship - See AIRSHIP STATION.
step - A break in the form of the bottom of a float or hull, designed to diminish resistance, to lessen the suction effects, and to improve control over longitudinal attitude. 
stern-droop - A deformation of an airship in which its longitudinal axis bends downward at the after end.
stern heavy - The condition in which, in normal flight, the after end of an airship tends to sink and which requires correction by means of the horizontal controls. It may be due to either aerodynamic or static conditions, or to both (cf. bowheavy).
stern-weighing device - An instrument located near the stern of an airship for measuring its buoyancy (cf. bow-weighing device).
stiffener, bow - A rigid member attached to the bow of a nonrigid or semirigid envelope to reinforce it against the pressure caused by the motion of the airship. (See figs. 3 and 4.)
sting - A light rod attached to and extending backward from a body for convenience of mounting when testing in a wind tunnel.
streamline - The path of a particle of a fluid, supposedly continuous, commonly taken relative to a solid body past which the fluid is moving; generally used only of such flows as are not eddying.
streamline flow - SEE FLOW, STREAMLINE.
streamline form - The form of a body so shaped that the flow about it tends to be a streamline flow. 
stresses, breathing - Stresses produced in an aerostat by breathing. They are of importance in the envelope and keel of a semirigid airship, due to the interaction of the envelope and keel when the envelope breathes.
strut - A compression member of a truss frame. (See fig. 5.)
  oleo strut - A shock-absorbing telescopic strut in which an oleo gear is incorporated.
stub plane - See STABILIIZER, STUB-WING.
sun compass - See COMPASS, SUN.
supercharge - To supply an engine with more air or mixture than would be inducted normally at the prevailing atmospheric pressure. The term supercharged is generally used to refer to conditions at altitudes where  the pressure in the intake manifold is partly or completely restored to that existing under normal operation at sea level (cf. boost).
supercharger - A pump for supplying the engine with a greater weight of air or mixture than would normally be inducted at the prevailing atmospheric pressure.
  centrifugal-type supercharger - A high-speed rotary blower equipped with one or more multi-blade impellers which, through centrifugal action, compress the air or mixture in the induction system.
  positive-driven-type supercharger - A supercharger driven at a fixed speed ratio from the engine shaft by gears or other positive means.
  reciprocating-type supercharger - A positive-displacement reciprocating pump in which the air or mixture is compressed by a piston working in a cylinder.
  Roots-type supercharger - A positive-displacement rotary blower consisting of two double-lobed impellers turning in opposite directions on parallel shafts within a housing, the impellers rolling together except for a small clearance, meanwhile alternately trapping incoming air or mixture in the ends of the housing and sweeping it through to the outlet.
  vane-type supercharger - A positive-displacement rotary blower having an eccentrically located rotor provided with one or more vanes.
supercharger control bypassing (Roots) - Regulating the pressure of the air supplied to the carburetor by discharging into the free atmosphere the excess delivered by the supercharger.