(Added to TC if the wind is from the right subtracted if wind is from the left) WCA-determined from the wind triangle.TC-direction of the line connecting two desired points, drawn on the chart and measured clockwise in degrees from TN on the mid-meridian.īriefly summarized, the steps in obtaining flight information are as follows: By placing the straight side of the protractor along the north-south line, with its center point at the intersection of the airspeed line and north-south line, read the TH directly in degrees (076°).The TH necessary to offset drift is indicated by the direction of the airspeed line, which can be determined in one of two ways: The distance flown in 1 hour (GS) is measured as the numbers of units on the TC line (88 NMPH or 88 knots). Draw the line and label it “AS 120.” The point “P” placed at the intersection represents the position of the aircraft at the end of 1 hour. Then place the ruler so that the end is on the arrowhead (W) and the 120-knot dot intercepts the TC line. The units used may be of any convenient scale or value (such as ¼ inch = 10 knots), but once selected, the same scale must be used for each of the linear movements involved. This can be represented by a diagram as shown in Figure 1.įinally, measure 120 units on the ruler to represent the airspeed, making a dot on the ruler at this point. If flight is to be made on a course to the east, with a wind blowing from the northeast, the aircraft must be headed somewhat to the north of east to counteract drift. Either consciously or unconsciously, every good pilot thinks of the flight in terms of wind triangle. The beginning student, however, needs to develop skill in constructing these diagrams as an aid to the complete understanding of wind effect. The experienced pilot becomes so familiar with the fundamental principles that estimates can be made that are adequate for visual flight without actually drawing the diagrams. It can be applied to the simplest kind of cross-country flight, as well as the most complicated instrument flight. GS, heading, and time for any flight can be determined by using the wind triangle. The wind triangle is a graphic explanation of the effect of wind upon flight. A wind triangle, the pilot’s version of vector analysis, is the basis of dead reckoning. Wind Triangle or Vector AnalysisIf there is no wind, the aircraft’s ground track is the same as the heading and the GS is the same as the true airspeed. The heading and GS, as calculated, is constantly monitored and corrected by pilotage as observed from checkpoints. Except for flights over water, dead reckoning is usually used with pilotage for cross-country flying. The predicted heading takes the aircraft along the intended path and the GS establishes the time to arrive at each checkpoint and the destination. The products derived from these variables, when adjusted by wind speed and velocity, are heading and GS. Dead reckoning is navigation solely by means of computations based on time, airspeed, distance, and direction.
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