Navigation

33 N 3 03 6 W E E P Course and groundspeed 24 12 21 S 15 Heading and airspeed W 16-14 yticolev dna noitcerid dniW N 080° heading and 120 knots airspeed Wind at 20° direction and 33 N 3 35 knots velocity 03 6 W E 090° course and 110 knots groundspeed 24 12 21 15 S S N S Figure 16-20. The wind triangle as is drawn in navigation practice. °01 so familiar with the fundamental principles that estimates can the blue, yellow, and black lines in Figure 16-20, which is be made that are adequate for visual flight without actually explained in the following example. drawing the diagrams. The beginning student, however, needs to develop skill in constructing these diagrams as an aid to the Suppose a flight is to be flown from E to P. Draw a line on complete understanding of wind effect. Either consciously or the aeronautical chart connecting these two points; measure unconsciously, every good pilot thinks of the flight in terms its direction with a protractor, or plotter, in reference to a of wind triangle. meridian. This is the TC, which in this example is assumed to be 090° (east). From the NWS, it is learned that the wind If flight is to be made on a course to the east, with a wind at the altitude of the intended flight is 40 knots from the blowing from the northeast, the aircraft must be headed northeast (045°). Since the NWS reports the wind speed in somewhat to the north of east to counteract drift. This can knots, if the true airspeed of the aircraft is 120 knots, there is be represented by a diagram as shown in Figure 16-19. Each no need to convert speeds from knots to mph or vice versa. line represents direction and speed. The long blue and white hashed line shows the direction the aircraft is heading, and Now, on a plain sheet of paper draw a vertical line representing its length represents the distance traveled at the indicated north to south. (The various steps are shown in Figure 16-21.) airspeed for 1 hour. The short blue arrow at the right shows the wind direction, and its length represents the wind velocity Step 1 for 1 hour. The solid yellow line shows the direction of the Place the protractor with the base resting on the vertical line track or the path of the aircraft as measured over the earth, and and the curved edge facing east. At the center point of the its length represents the distance traveled in 1 hour or the GS. base, make a dot labeled “E” (point of departure) and at the curved edge, make a dot at 90° (indicating the direction of the In actual practice, the triangle illustrated in Figure 16-19 is true course) and another at 45° (indicating wind direction). not drawn; instead, construct a similar triangle as shown by Drift Angle 8° left correction Figure 16-19. Principle of the wind triangle.