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May, 1911     AVIATION   
 
NEW INSTRUMENTS FOR THE AEROPLANE
By Buel H. Green.

Combination Instrument Indicating Velocity, the Angle of Flight, and Angle of Ascent and Descent.

This instrument is to be placed on an aeroplane to determine at any time the angle at which the aeroplane is ascending or descending, that is, the angle made with the horizon in degrees with the direction followed by the aeroplanes; the angle of attack of the planes - that angle formed between the chord of the planes and the direction of the flight; and the speed of the aeroplane in relation of still air.

[[image: drawing of an aeronautical measuring instrument]]
[[caption]] Combination Instrument Indicating Velocity, the Angle of Flight, and Angle of Ascent and Descent [[/caption]]

DESCRIPTION

The body of this apparatus is prismatic in form, and is fixed by an adjustable bracket to the frame work of the aeroplane. Inside of the body of the instrument is a glass tube filled with a colored liquid, back of which is placed a scale. The liquid in this tube by its position in front of the scale shows the angle of attack in degrees. If the liquid rests at zero on the scale the aeroplane is moving in a horizontal direction, if the liquid is above zero the aeroplane is descending, and if below zero the aeroplane is ascending.

The graduations indicate in degrees the angle of flight in relation to the horizontal. The body of this apparatus also carries on the front edge an index before which another pointer moves to indicate the angle of the planes. When the pointer rests at zero on the scale the chord of the wings should be horizontal, then when the pointer is above or below zero the angle of attack is shown in degrees above or below the horizontal, thus permitting the aviator at all times to know the angle of attack whether it be positive or negative. The third scale nearest the axis of the apparatus is graduated to indicate velocity of the apparatus in relation to still air, in kilometers per hour. The pointer moving over this scale is connected to a small anemometer which causes the pointer to move over the scale as the speed of the aeroplane increases in relation to still air.

Hand Anemometer

This apparatus should be held vertically by the handle around which the sector may turn. The exact vertical position is indicated by a small level attached to the base of the segament. The speed of the wind is indicated by