Figure 12-8.  Station pressure is converted to and reported in sea level pressure.  Altitude affects every aspect of flight from aircraft  performance to human performance. At higher altitudes,  with a decreased atmospheric pressure, takeoff and landing  distances are increased, while climb rates decrease.  When an aircraft takes off, lift is created by the flow of air  around the wings. If the air is thin, more speed is required  to obtain enough lift for takeoff; therefore, the ground run  is longer. An aircraft that requires 745 feet of ground run at  sea level requires more than double that at a pressure altitude of 8,000 feet.  [Figure 12-9] . It is also true that at higher  altitudes, due to the decreased density of the air, aircraft engines and propellers are less efficient. This leads to reduced  rates of climb and a greater ground run for obstacle clearance.  As discussed earlier, nitrogen and other trace gases make  up 79 percent of the atmosphere, while the remaining 21  Figure 12-9.  Takeoff distances increase with increased altitude.  Altitude and the Human Body Altitude and Flight 12-6  Standard Atmosphere  Denver 29.92 "Hg  24.92  " Hg  Station Pressure  Denver  29.92  " Hg  Station Pressure  New Orleans  New Orleans 29.92 "Hg  1,590 feet  745 feet  Pressure Altitude: Sea level  Pressure Altitude: 8,000 feet  TAKEOFF DISTANCE  MAXIMUM WEIGHT 2,400 LB  Pressure  altitude  (feet)  S.L.  1,000  2,000  3,000  4,000  5,000  6,000  7,000  8,000  Ground  roll  (feet)  745  815  895  980  1,075  1,185  1,305  1,440  1,590  Total feet  to clear  50 foot obstacle  1,320  1,445  1,585  1,740  1,920  2,125  2,360  2,635  2,960  0 °C 