Flight Manuals and Placards Placards Glider Polars Performance Information The GFM/POH provides the pilot with the necessary  performance information to operate the glider safely. A GFM/ POH may include the following information: particular types of gliders. Gliders with wing flaps, for instance,  have a maximum permitted flaps extended airspeed (V$_{FE}$). Manuals for self-launching gliders include performance  information about powered operations. These include rate of  climb, engine and propeller limitations, fuel consumption,  endurance, and cruise. In addition, the manufacturer provides information about the  rate of sink in terms of airspeed, which is summarized in a  graph called a polar curve, or simply a polar.  [Figures 5-11] The vertical axis of the polar shows the sink rate in knots  (increasing sink downwards), while the horizontal axis shows  airspeed in knots. Every type of glider has a characteristic  polar derived either from theoretical calculations by the  designer or by actual in-flight measurement of the sink rate  at different speeds. The polar of each individual glider varies  (even from other gliders of the same type) by a few percent  depending on relative smoothness of the wing surface, the  amount of sealing around control surfaces, and even the  number of bugs on the wing’s leading edge. The polar forms  the basis for speed to fly and final glide tools that will be  discussed in Chapter 11, Cross-Country Soaring. •  Description of glider primary components •  Glider assembly •  Weight and balance data •  Description of glider systems •  Glider performance •  Operating limitations Cockpit placards provide the pilot with readily available  information that is essential for the safe operation of the  glider. All required placards are located in the GFM/POH. The amount of information that placards must convey to  the pilot increases as the complexity of the glider increases.  High performance gliders may be equipped with wing flaps,  retractable landing gear, a water ballast system, drogue chute  for use in the landing approach, and other features that are  intended to enhance performance. These gliders may require  additional placards.  [Figure 5-10] Minimum sink rate is determined from the polar by extending  a horizontal line from the top of the polar to the vertical axis.  [Figure 5-12]  In this example, a minimum sink of 1.9 knots  occurs at 40 knots. Note that the sink rate increases between  minimum sink speed and the stall speed (the left end point of  the polar). The best glide speed (best L/D) is found by drawing  a tangent to the polar from the origin. The best L/D speed is  50 knots with a sink speed of 2.1 knots. The glide ratio at best  The GFM/POH is the source provided by the manufacturer  for glider performance information. In the GFM/POH, glider  performance is presented in terms of specific airspeed, such  as stall speed, minimum sinking airspeed, best L/D airspeed,  maneuvering speed, rough air speed, and the never exceed  speed (V$_{NE}$ ). Some performance airspeeds apply only to  Glider Self-Launching Glider After inflight engine shutdown,  feather propeller DO NOT EXCEED 6,400 Engine rpm OFF EMERGENCY CANOPY JETTISON Minimum pilot seat weight—154 lb (70 kg) Maximum pilot seat weight—264 lb (120 kg) INTENTIONAL SPINNING PROHIBITED Stall speed—35 knots Maximum ground launch speed—74 knots Maneuvering speed—86 knots Maximum aerotow speed—94 knots V$_{NE}$—136 knots Figure 5-10.  Typical placards for nonmotorized and self-launching gliders. 5-8