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## Flight Manuals and Placards 

The GFM/POH provides the pilot with the necessary performance information to operate the glider safely. A GFM/ POH may include the following information: 

• Description of glider primary components 

• Glider assembly 

• Weight and balance data 

• Description of glider systems 

• Glider performance 

• Operating limitations 

## Placards 

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] 

## Performance Information 

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 

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. 

## Glider Polars 

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. 

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 

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