Glider specifications Glide ratio (L/D) = 30:1 Speed (GRA) = 50 knots Tailwind component Wind = +10 knots 50 + 10 = 60 60/50 = 1.2 1.2 x 30 = 36 Effective glide ratio (L/D) is 36:1 Headwind component Wind = −10 knots 50 − 10 = 40 40/50 = 0.8 0.8 x 30 = 24 Effective glide ratio (L/D) is 24:1 GRA ± Wind GRA x L/D = Effective L/D ( ) Using the Plotter Measuring distance with the plotter is accomplished by  using the straight edge. Use the Albuquerque sectional  chart and measure the distance between Portales Airport  (Q34) and Benger Airport (Q54), by setting the plotter with  the zero mark on Portales. Read the distance of 47 nautical  miles (NM) to Benger. Make sure to set the plotter with the  sectional scale if using a sectional chart (as opposed to the  WAC scale), otherwise the measurement will be off by a  factor of two.  [Figure 11-5] The true heading between Portales and Benger can be  determined by setting the top of the straightedge along the  course line, then slide it along until the index hole is on a line  of longitude intersecting the course line. Read the true heading  on the outer scale, in this case, 48°. The outer scale should be  used for headings with an easterly component. If the course  were reversed, flying from Benger to Portales, use the inner  scale, for a westerly component, to find 228°.  [Figure 11-6] Many models of electronic glide calculators now exist. Often  coupled with an electronic variometer, they display the  altitude necessary for distance and wind as input by the pilot.  In addition, many electronic glide calculators feature speed- to-fly functions that indicate whether the pilot should fly  faster or slower. Most electronic speed-to-fly directors include  audio indications, so the pilot can remain visually focused  outside the cockpit. The pilot should have manual backups  for electronic glide calculators and speed-to-fly directors in  case of a low battery or other electronic system failure. A common error when first using the plotter is to read the  course heading 180° in error. This error is easy to make by  reading the scale marked W 270° instead of the scale marked E  09°. For example, the course from Portales to Benger is towards  the northeast, so the heading should be somewhere between  30° and 60°, therefore the true heading of 48° is reasonable. For training purposes, plan a triangle course starting at  Portales Airport (PRZ), with turn points at Benger Airport  (X54), and the town of Circle Back. As part of the preflight  preparation, draw the course lines for the three legs. Using  the plotter, determine the true heading for each leg, then  correct for variation and make a written note of the magnetic  heading on each leg. Use 9° east (E) variation as indicated  on the sectional chart (subtract easterly variations, and add  westerly variations). The first leg distance is 47 NM with a  heading of 48° (48° – 9° E = 39° magnetic); the second leg is  38 NM at 178° true (178° – 9° E = 169° magnetic); the third  leg is 38 NM at 282° true (282° – 9° E = 273° magnetic).  [Figure 11-7] Other equipment may be needed to verify soaring performance  to receive a Federation Aeronautique Internationale (FAI) badge  or record flights. These include turn-point cameras, barographs,  and GPS flight recorders. For complete descriptions of these  items, as well as badge or record rules, check the Soaring  Society of America website (www.ssa.org) for details. Finally, a notepad or small leg-attached clipboard on which to  make notes before and during the flight is often handy. Notes  prior to flight could include weather information such as winds  aloft forecasts or distance between turn points. In flight, noting  takeoff and start time, as well as time around any turn points,  is useful to gauge average speed around the course. Assume the base of the cumulus is forecast to be 11,000 MSL,  and the winds aloft indicate 320° at 10 knots at 9,000 MSL  and 330° at 20 knots at 12,000 MSL. Make a written note of  the winds aloft for reference during the flight. For instance,  the first leg has almost a direct crosswind from the left; on the  second leg, a weaker crosswind component from the right;  while the final leg is almost directly into the wind. Knowing  courses and approximate headings aids the navigation and  helps avoid getting lost, even though deviations to stay with  the best lift are needed. During the flight, if the sky ahead  Airplane pilots navigate by pilotage (flying by reference to  ground landmarks) or dead reckoning (computing a heading  from true airspeed and wind, and then estimating time  needed to fly to a destination). Glider pilots use pilotage  since they generally cannot remain on a course line over a  long distance and do not fly one speed for any length of time.  Nonetheless, it is important to be familiar with the concepts  of dead reckoning since a combination of the two methods  is sometimes needed. 11-5 Navigation A Sample Cross-Country Flight Figure 11-4.  Glide calculation example.