Pilots should become familiar with all the operating  limitations of each glider being flown.  Figure 5-18  shows four  different possible conditions and the basic flight envelope for  a high performance glider. If the CG is within limits, pitch attitude control stays within  acceptable limits. However, if the glider is loaded so the CG  is forward of the forward limit, handling is compromised.  The glider is said to be nose heavy. Nose heaviness makes  it difficult to raise the nose on takeoff and considerable back  pressure on the control stick is required to control the pitch  attitude. Tail stalls occur at airspeeds higher than normal and  are followed by a rapid nose-down pitch tendency. Restoring  a normal flight attitude during stall recoveries takes longer.  The landing flare is more difficult than normal, or perhaps  even impossible, due to nose heaviness. Inability to flare  could result in a hard nose-first landing. Longitudinal balance affects the stability of the longitudinal  axis of the glider. To achieve satisfactory pitch attitude handling  in a glider, the CG of the properly loaded glider is forward of  the center of pressure (CP). When a glider is produced, the  manufacturer provides glider CG limitations, which require  compliance. These limitations are generally found in the GFM/ POH and may also be found in the glider airframe logbook.  Addition or removal of equipment, such as radios, batteries,  or flight instruments, or airframe repairs can have an effect on  the CG position. Aviation maintenance technicians (AMTs)  must record any changes in the weight and balance data in the  GFM/POH or glider airframe logbook. Weight and balance  placards in the cockpit must also be updated. The following are the most common reasons for CG forward  of forward limit: Weight and Balance Center of Gravity Problems Associated With CG Forward of Forward  Limit Figure 5-18.  Typical example of basic flight envelope for a high-performance glider. •  Pilot weight exceeds the maximum permitted pilot  weight. •  Seat or nose ballast weights are installed but are not  required due to the weight of the pilot. N Limit wing load factor (“G” units) V = Velocity (mph) +6.0 +5.0 +4.0 +3.0 +2.0 +1.0 0.0 −1.0 −2.0 −3.0 −4.0 SGS 1-35 Basic Flight Envelope High Performance Class Cond III Pos. Gust L.F. = 3.55 I II III IV Cond IV Neg. Gust L.F. = 3.55 Cond II Neg. Man. L.F. = 2.67 Cond I Pos. Man. L.F. = 5.33 V G  = 154 MPH POSITIVE 24 FPS GUST FACTOR NEGATIVE 24 FPS GUST FACTOR 0  20 40 60 80 100 120 140 160 180 200 220 L.F. –  Load Factor Neg. Negative Pos. – Positive FPS –  Feet per second 5-12