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Figure 16-21. Steps in drawing the wind triangle. 16-15 90 N 10 20 30 40 50 60 70 80 001 071 061 051 041 031 021 011 33 N 3 03 6 W E E P 24 21 S 15 A 12 irspeed 1 T 2 C 0 0 k 9 n 0 o ° ts GS 88 W S 90 10 20 30 40 50 60 70 80 001 011 021 031 041 051 071 061 90 10 20 30 STEP 1 40 N STEP 2 and 3 504 5° 60 Mid point 70 980 0° E TC 090° 1 0 0 Wi n d 011 021 031 W 041 S 051 071 061 STEP 4 Step 2 • By placing the straight side of the protractor along With the ruler, draw the true course line from E, extending it the north-south line, with its center point at the somewhat beyond the dot by 90°, and labeling it “TC 090°.” intersection of the airspeed line and north-south line, read the TH directly in degrees (076°). [Figure 16-22] Step 3 • By placing the straight side of the protractor along the Next, align the ruler with E and the dot at 45°, and draw TC line, with its center at P, read the angle between the wind arrow from E, not toward 045°, but downwind in the TC and the airspeed line. This is the WCA, which the direction the wind is blowing making it 40 units long to must be applied to the TC to obtain the TH. If the wind correspond with the wind velocity of 40 knots. Identify this blows from the right of TC, the angle is added; if from line as the wind line by placing the letter “W” at the end to the left, it is subtracted. In the example given, the show the wind direction. WCA is 14° and the wind is from the left; therefore, subtract 14° from TC of 090°, making the TH 076°. Step 4 [Figure 16-23] Finally, measure 120 units on the ruler to represent the After obtaining the TH, apply the correction for magnetic airspeed, making a dot on the ruler at this point. The units variation to obtain magnetic heading and the correction used may be of any convenient scale or value (such as ¼ for compass deviation to obtain a compass heading. The inch = 10 knots), but once selected, the same scale must compass heading can be used to fly to the destination by be used for each of the linear movements involved. Then dead reckoning. place the ruler so that the end is on the arrowhead (W) and the 120-knot dot intercepts the TC line. Draw the line and To determine the time and fuel required for the flight, first label it “AS 120.” The point “P” placed at the intersection find the distance to your destination by measuring the length represents the position of the aircraft at the end of 1 hour. of the course line drawn on the aeronautical chart (using the The diagram is now complete. appropriate scale at the bottom of the chart). If the distance measures 220 NM, divide by the GS of 88 knots, which gives The distance flown in 1 hour (GS) is measured as the numbers 2.5 hours, or 2:30, as the time required. If fuel consumption of units on the TC line (88 NMPH or 88 knots). The TH is 8 gallons an hour, 8 × 2.5 or about 20 gallons is used. necessary to offset drift is indicated by the direction of the airspeed line, which can be determined in one of two ways: