90  80  70  60  30  20  10  170  160  150  140  130  120  110  100  70  60  50   40  30  170  160  150  140  130  120  110  90  80  70  60  50  40  30 20 10  170 160 150  140  130  120  110  100  Airspeed 120 knots TC 090° GS 88  N  3 3  3 0  W 2 4  2 1  S  1 5  $_{1}$2 $^{E }$ 6  3  P  W  E N  S  50  40  90  80  100  W  E  N  S  TC 090°  Wind  Mid point STEP 1 STEP 4  STEP 2 and 3 4  5  °  9  0  °  Figure 16-21.  Steps in drawing the wind triangle.  Step 2  Step 3  Step 4  With the ruler, draw the true course line from E, extending it  somewhat beyond the dot by 90°, and labeling it “TC 090°.”  Next, align the ruler with E and the dot at 45°, and draw  the wind arrow from E, not toward 045°, but downwind in  the direction the wind is blowing making it 40 units long to  correspond with the wind velocity of 40 knots. Identify this  line as the wind line by placing the letter “W” at the end to  show the wind direction.  Finally, measure 120 units on the ruler to represent the  airspeed, making a dot on the ruler at this point. 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. Then  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  label it “AS 120.” The point “P” placed at the intersection  represents the position of the aircraft at the end of 1 hour.  The diagram is now complete.  The distance flown in 1 hour (GS) is measured as the numbers  of units on the TC line (88 NMPH or 88 knots). The TH  necessary to offset drift is indicated by the direction of the  airspeed line, which can be determined in one of two ways:  To determine the time and fuel required for the flight, first  find the distance to your destination by measuring the length  of the course line drawn on the aeronautical chart (using the  appropriate scale at the bottom of the chart). If the distance  measures 220 NM, divide by the GS of 88 knots, which gives  2.5 hours, or 2:30, as the time required. If fuel consumption  is 8 gallons an hour, 8  × 2.5 or about 20 gallons is used.  After obtaining the TH, apply the correction for magnetic  variation to obtain magnetic heading and the correction  for compass deviation to obtain a compass heading. The  compass heading can be used to fly to the destination by  dead reckoning.  16-15  • 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°).  [Figure 16-22]  • By placing the straight side of the protractor along the  TC line, with its center at P, read the angle between  the TC and the airspeed line. This is the WCA, which  must be applied to the TC to obtain the TH. If the wind  blows from the right of TC, the angle is added; if from  the left, it is subtracted. In the example given, the  WCA is 14° and the wind is from the left; therefore,  subtract 14° from TC of 090°, making the TH 076°.  [Figure 16-23] 