Fecha de publicación: 24/04/1919 Fuente: WIPO "pollen" 125,467. Pollen, A. H., and Chicken, C. B. Aug. 17, 1916. Speed indicators operating by sighting terrestrial objects.-Relates to ground-speed measuring- apparatus for aircraft, of the kind in which a sighting-arm is rotatably mounted on a transverse horizontal axis and is moved at such a rate that the observed objects on the ground appear to be stationary in the field of view; the apparatus being also rotatable horizontally to measure the angle of drift. In the present construction, the sighting-arm 11, Fig. 3, carrying sights 52, 53, is mounted on the axis 12 and is given a uniform but adjustable horizontal speed by means of a pin which slides in the slot 11 and forms the spindle of a roller 10 having a block sliding in the horizontal slot 49. The roller 10 is given a uniform movement in one direction by a snail cam 9 which is driven by a motor 1, through disk-and-roller mechanism 2, 3, 4 and bevel-gear 5, 7, a quick return being effected by the spring 51. The speed of the cam is varied by adjustment of the roller 3 by means of a rack and pinion 21, 22, spur gears 23, and knob 24 actuating an indicator 26. The vertical distance between the sight pivot 12 and the slot 49 is adjusted according to the height of flight by mounting the pivot on a block 13 forming a nut on a screw 15. The turning knob 16 is connected by bevel gear to a graduated ring 18 beside a pointer. The apparatus can be rotated as a whole about a vertical pivot 28, by means of the gearing 30, 31, and knob 32 fitted with a drift indicator 35, until the terrestrial stream lines coincide in direction with the wire 33. The speed of the motor 1 is regulated by a governor 54 fitted with a disk against which a pin is pressed, adjustment being effected through the knob 41.