Part 17 (2/2)

=Angle of Incidence=--The angle at which the ”neutral lift line” of a surface attacks the air.

=Angle of Incidence, Rigger's=--The angle the chord of a surface makes with a line parallel to the axis of the propeller.

=Angle of Incidence, Maximum=--The greatest angle of incidence at which, for a given power, surface (including detrimental surface), and weight, horizontal flight can be maintained.

=Angle of Incidence, Minimum=--The smallest angle of incidence at which, for a given power, surface (including detrimental surface), and weight, horizontal flight can be maintained.

=Angle of Incidence, Best Climbing=--That angle of incidence at which an aeroplane ascends quickest. An angle approximately halfway between the maximum and optimum angles.

=Angle of Incidence, Optimum=--The angle of incidence at which the lift-drift ratio is the highest.

=Angle, Gliding=--The angle between the horizontal and the path along which an aeroplane, at normal flying speed, but not under engine power, descends in still air.

=Angle, Dihedral=--The angle between two planes.

=Angle, Lateral Dihedral=--The lifting surface of an aeroplane is said to be at a lateral dihedral angle when it is inclined upward towards its wing-tips.

=Angle, Longitudinal Dihedral=--The main surface and tail surface are said to be at a longitudinal dihedral angle when the projections of their neutral lift lines meet and produce an angle above them.

=Angle, Rigger's Longitudinal Dihedral=--Ditto, but subst.i.tuting ”chords”

for ”neutral lift lines.”

=Angle, Pitch=--The angle at any given point of a propeller, at which the blade is inclined to the direction of motion when the propeller is revolving but the aeroplane stationary.

=Altimeter=--An instrument used for measuring height.

=Air-Speed Indicator=--An instrument used for measuring air pressures or velocities. It consequently indicates whether the surface is securing the requisite reaction for flight. Usually calibrated in miles per hour, in which case it indicates the correct number of miles per hour at only one alt.i.tude. This is owing to the density of the air decreasing with increase of alt.i.tude and necessitating a greater speed through s.p.a.ce to secure the same air pressure as would be secured by less speed at a lower alt.i.tude. It would be more correct to calibrate it in units of air pressure. [1]

=Air Pocket=--A local movement or condition of the air causing an aeroplane to drop or lose its correct att.i.tude.

=Aspect-Ratio=--The proportion of span to chord of a surface.

=Air-Screw (Propeller)=--A surface so shaped that its rotation about an axis produces a force (thrust) in the direction of its axis. [2]

=Aileron=--A controlling surface, usually situated at the wing-tip, the operation of which turns an aeroplane about its longitudinal axis; causes an aeroplane to tilt sideways. [3]

=Aviation=--The art of driving an aeroplane.

=Aviator=--The driver of an aeroplane.

=Barograph=--A recording barometer, the charts of which can be calibrated for showing air density or height.

=Barometer=--An instrument used for indicating the density of air.

=Bank, to=--To turn an aeroplane about its longitudinal axis (to tilt sideways) when turning to left or right.

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