28.00 −40  −20  0  +20  +40 29.00 29.92 31.92 Ambient temperature −°C Engine pressure ratio − P †7 /P †2 Turbine discharge pressure − P$_{†7}$ −IN. H g Field barometric pressure "Hg Interpolate to locate these  points Example: Ambient temperature = 20°C Field barometric  pressure = 30.50 "Hg Adjust throttle to obtain EPR  determined at point A or the R$_{†7}$  valve determined at point B Burner pressure limit 24.00 25.00 26.00 27.00 28.00 29.00 30.00 31.00 A B Figure 10-74.  Typical takeoff thrust setting curve for static conditions.  the static field or true barometric pressure, and not  the barometric pressure corrected to sea level that  is normally reported by airport control towers as the  altimeter setting. On FADEC engines, the computer  reads this information and sends it to the engine  controls. On turbine engines that have a thrust reverser, retarding the  aircraft throttle to idle or power lever to OFF cuts the fuel  supply to the engine and shuts down the engine. On engines  equipped with thrust reversers, this is accomplished by  means of a separate fuel shutoff lever or switch. When an  engine has been operated at high power levels for extended  To ensure that fuel remains in the lines and that the engine- driven fuel pumps are not starved for fuel that lubricates the  pumps, the aircraft fuel boost pump must be turned off after,  periods of time, a cool down time should be allowed before  shutting down. It is recommended the engine be operated  at below a low power setting, preferably at idle for a period  of 5 minutes to prevent possible seizure of the rotors. This  applies, in particular, to prolonged operation at high rpm on  the ground, such as during engine trimming. The turbine  case and the turbine wheels operate at approximately the  same temperature when the engine is running. However,  the turbine wheels are relatively massive, compared with  the case, and are not cooled so readily. The turbine case  is exposed to cooling air from both inside and outside the  engine. Consequently, the case and the wheels lose their  residual heat at different rates after the engine has been shut  down. The case, cooling faster, tends to shrink upon the  wheels, that are still rotating. Under extreme conditions, the  turbine blades may squeal or seize; thus, a cooling period is  required if the engine has been operating at prolonged high  speed. Should the turbine wheels seize, no harm normally  results, provided no attempt is made to turn the engine over  until it has cooled sufficiently to free the wheels. In spite of  this, every effort should be made to avoid seizure. 2.  Temperature sensed is the total air temperature (TAT)  that is used by several onboard computers. The engine  controls set the engine computers according to the  TAT.  3.  Relative humidity, which affects reciprocating engine  power appreciably, has a negligible effect on turbine  engine thrust, fuel flow, and rpm. Therefore, relative  humidity is not usually considered when computing  thrust for takeoff or determining fuel flow and rpm  for routine operation. Engine Shutdown 10-59