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Aviation History
1929
1929 - 1029.PDF
FLIGHT, MAY 16, 1929 HUGHES-WAAGE COURSE CORRECTOR An Instrument of Interest to Air Navigators THE corrector has two discs, both withcompass roses. The discs are con-nected by an arrangement which only permits a relative parallel movement. While thus arranged, the north-south line on both discs and any two corresponding lines will be parallel in any relative position of discs. On the white celluloid disc radial lines are drawn every five degrees. The cardinal and quadrantal points are marked by their letters on both discs. On the transparent disc, only the north-south and east-west lines are fully drawn, in order to fix centre precisely. On the white disc are drawn circles, the radius interval of which are one-tenth of the radius of the tenth circle. The corrector is based on the well-known principle that the speed and direction of wind are found by two drift observations on two different courses. The drift can be read on a simple instru- ment. The aircraft can also be fitted with a graduation on the tail plane for drift reading. To make clearer the use of the corrector the latter method will be dealt with. Fig. 1. The two diopters near the observer's seat are centres of the graduation on the tail plane. Every five degrees are marked with a streak, as shown on the figure. In order to read the drift, you should determine the point of the graduation where a line from diopter cuts which is so that some point on earth will remain in it, when flying a steady compass course. When following a line that cuts the graduation in a point to one or another side of the correct point, you will see that the point on earth in prolongation of the line is moving out of it. The correct point on the graduation found, you can read the drift in number of degrees on the tail plane directly. On the right side of the tail plane is painted a minus — sign, on left side a plus — sign. Plus and minus are put on so because the drift measured on the right side of the tail plane has a clockwise direction , RIGHT V / V FIG / / V 4- N —r 4 ^^ A N' O1 / %\ CLAMPING SCREW Hughes-Waage Course Corrector, and the drift measured on the left side^an anti-clockwisedirection out of compass course. * Fig. 2 shows the geometric proof of the fact that speedand direction of wind can be found when the angles of drift on two different courses are known. The length of the radius of circle is indifferent. North-south line is laid off through the centre. The radii OA and OB represent known compass courses, Oa and Ob respectivecourses made good laid off by the known angles of drift x and y. The length of the radii OA and OB further represents theairspeed of the craft, which is the same on any course. The problem then is to complete two triangles of velocities. AH and BF must represent the wind in magnitude anddirection and, therefore, they must be of equal length and parallel. The construction of AH and BF is done by the following method :— From C lay off CD = AB. Through D lay off a line parallelto Oa. This line cuts Ob in F. Joining B and F the triangle of velocities OBF is completed. To complete the other triangle AOH youonly have to lay off from A a line parallel to BF. Then AH must be of the samelength as BF. Having determined speed and directionof wind, you can lay off several compass courses in the circle and complete therespective triangle of velocities. Fig. i3. You will then note that the point of inter-section between lines representing wind land ground speed describe a circle with a radiusequal to that of the first circle. The circles are marked Nos. 1 and 2.A line between the centres of the circles are equal to the line representing wind inmagnitude and direction. Fig. 4. The position of circle No. 2represents a certain wind. It is shown that a compass graduation on circle No. 1 is quitesimply transferred to circle No. 2 by drawing lines equal to 00' in magnitude and directionfrom each point on circle No. 1 to circle No. 2. The circle No. 2 therefore is movedparallel away from circle No. 1 by action of wind. On the figure is laid off a compass courseOK, and thereafter the triangle of velocities OKB is completed. The point of graduation Q' 403
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