Patent GB-429717-A (GB)
Title: Improvements in navigating and calculating apparatus for aircraft
IPC: B64D43/00
Filed: 1934-08-10
Abstract: 429,717. Speedometers; plane-trigonometry calculators. COLVIN, C. H., Egbert Hill, Morristown, New Jersey, U.S.A. Aug. 10, 1934, No. 23129. Convention date, Aug. 11, 1933. [Classes 106 (i) and 106 (iii)] Comprises an instrument for indicating a function of the speed of an aircraft relatively to the ground, wherein said speed is determined as a function of the air speed of the craft, of a component of the wind velocity and of the angle of drift. In Fig. 2 QO represents the air-speed v of the craft in the direction of heading, OP represents w the wind velocity, and QP represents the velocity V relatively to the ground. The angle OQP is the angle of drift #. The angle alpha is the difference between the angle # representing direction of heading, measured from the North, and the angle p representing the direction of the wind measured from the North. From the triangle OR = W cos alpha, QR = a + W cos alpha and QP = V = v + W cosalpha / cos # . The distance travelled is f V dt. The apparatus is shown diagrammatically in Fig. 4, connections between many elements being omitted for clearness, and major elements being given a reference letter which represents both the element itself and the axis about which it turns. An electric motor or other constant speed device A drives the " air-speed " cone B and " component wind cone D through appropriate gears. Driven by the cone B is an " air-speed " wheel C the speed of which depends on the distance of C from the apex of the cone as well as on A. The wheel C is traversed by a screw 41 moved by the knob 21, an index 31 moving over a scale 36. Driven from D is a " component-wind " wheel E the position of which along the cone is determined by the position of a block 62 movable both angularly and radially with respect to the axis O. The radial position is controlled by a knob 22 and the distance from the axis O is indicated by an index 53 on a scale 58 in units of wind velocity. The knob 23 can be used to orient the block 62 and index 43 in reference to the dial 38 and index 33, or to orient the block 62, index 43 and dial 38 in reference to the index 33. The block 62 through the part 63 moves the wheel E over D. The distance of the block 62 above or below the axis O is W cos alpha indicated by the index 32 on the scale 37. The diameter of the cone at the position of contact with the wheel where W cos alpha = O may be made equal to the diameter of the wheel E and therefore the speeds of E and D equal at this point. Since the diameter of the cone at the distance e from the apex is Ke where K is a constant, the diameter of the wheel is Keo where e‹ is the distance e when Wcosalpha = O. If the speed of the cone is d, the speed of the wheel is de / e<0> . Since e = e<0> + Wcosalpha, the speed of wheel E is d + d Wcos alpha / e<0>. The distance QO is determined as a function of air-speed by means of the knob 21 in the same operation as the adjustment of the wheel C. The index 33 represents direction of heading # and the index 43 direction of wind s on scale 38. An index 431 displaced 180‹ from the index 43 reads direction from which the wind blows. Means described with reference to the Figures transfer the indication of the angle # to the index 44 on the scale 49 of which the index 33 is the zero mark. The shaft of the wheel E drives one input side E<1> of a differential gear system E<1>D<1>F, the other input side D<1> of which is driven by the shaft of the cone D. The gear is designed so that output speed F is the difference between the input speeds of E<1> and D<1> i.e. a function of W cos alpha. The shaft C is connected to one input side C<1> of a second differential gear system C<1>F<1>G. To the other input side F<1> is connected the output shaft F of gear E<1>D<1>F so that the shaft C<1> turns at a speed of K2V and F<1> at a speed of K2W cos alpha, K2 being constant. The gear is designed so that the output speed of shaft G is the sum of the speeds of C<1> and F<1> that is proportional to v + W cos alpha which is the speed in the direction of heading. This is the speed of the " Drift Wheel " G. The speed of the cone H is a direct function of the speed of G and an inverse function of the distance g of their point of contact from the apex of the cone. The latter is determined by a block 64 which is oriented about the axis O at a fixed radius. The angular position " # " of block 64 is indicated by a pointer 54 on scale 49. The block and index are controlled by a knob 24 which also controls any position of the synchronizer N. By bringing the pointer 54 into coincidence with the pointer 44 the angle " # " may be made equal to " # ". The block 64 through the part 65 moves the wheel G and a pointer 34 indicates " Drift angle " on a scale 39. The distance of the wheel G from the apex of the cone H when " # " is equal to " # " is proportional to cos # and therefore the speed of the cone H to v + W cos alpha / cos # which is V the speed over the ground. A counter M is driven from the cone H and the distance integrated and registered. A tachometer T may be also driven from the cone H. The ground speed may be obtained indirectly from scales 36, 37, 39. The cone H drives directly or through gearing an " altitude " wheel J the speed of which is proportional to V and this wheel J drives a cone K the speed of which depends also on the position of the wheel J which is moved by a knob 25 and screw 55, an index 35 moving over a height scale 40. The speed of the cone is thus a function of V / H and the cone drives a shaft L of a synchronizer unit N which may be of the form described in Specification 414,881 and is adapted to show actual or apparent linear motion in reference to the earth and to be oriented about a vertical axis. The knob 24 controls orientation of the synchronizer. The details of the actual construction of the instrument and the mechanisms connecting the parts referred to in the diagrammatic form are described with reference to other Figures. The problems to be solved by the device are :-(1) Knowing the air speed, altitude and heading, and observing the ground, (a) the angle of drift, (b) course, (c) the direction of the wind, (d) the velocity of the wind, (e) the ground speed and (f) the distance travelled in respect to the ground may be determined. (2) Knowing the direction and velocity of the wind, (a) the angle of drift, (b) the course, (c) the ground speed, and (d) the ground distance for any heading and any air speed may be determined. (3) By maintaining the positions of the various indicators of the device in accordance with the known or determined air speed, heading, drift and wind, a continuous log of the ground distance can be determined.