detonation, which in turn can cause catastrophic engine failure.  Turbocharged engines are especially heat sensitive. The key  to turbocharger operation is effective heat management. When the waste gate is open, the turbocharged engine reacts  the same as a normally aspirated engine when the rpm is  varied. That is, when the rpm is increased, the manifold  pressure decreases slightly. When the engine rpm is  decreased, the manifold pressure increases slightly. However,  when the waste gate is closed, manifold pressure variation  with engine rpm is just the opposite of the normally aspirated  engine. An increase in engine rpm results in an increase in  manifold pressure, and a decrease in engine rpm results in a  decrease in manifold pressure. Monitor the condition of a turbocharged engine with manifold  pressure gauge, tachometer, exhaust gas temperature/turbine  inlet temperature gauge, and cylinder head temperature.  Manage the “heat system” with the throttle, propeller rpm,  mixture, and cowl flaps. At any given cruise power, the mixture  is the most influential control over the exhaust gas/TIT. The  throttle regulates total fuel flow, but the mixture governs the  fuel to air ratio. The mixture, therefore, controls temperature. Above the critical altitude, where the waste gate is closed,  any change in airspeed results in a corresponding change in  manifold pressure. This is true because the increase in ram  air pressure with an increase in airspeed is magnified by the  compressor resulting in an increase in manifold pressure.  The increase in manifold pressure creates a higher mass flow  through the engine, causing higher turbine speeds and thus  further increasing manifold pressure. Exceeding temperature limits in an after takeoff climb is  usually not a problem since a full rich mixture cools with  excess fuel. At cruise, power is normally reduced and  mixture adjusted accordingly. Under cruise conditions,  monitor temperature limits closely because that is when the  temperatures are most likely to reach the maximum, even  though the engine is producing less power. Overheating in  an en route climb, however, may require fully open cowl  flaps and a higher airspeed. When running at high altitudes, aviation gasoline may tend  to vaporize prior to reaching the cylinder. If this occurs in the  portion of the fuel system between the fuel tank and the engine- driven fuel pump, an auxiliary positive pressure pump may  be needed in the tank. Since engine-driven pumps pull fuel,  they are easily vapor locked. A boost pump provides positive  pressure—pushes the fuel—reducing the tendency to vaporize. Since turbocharged engines operate hotter at altitude than do  normally aspirated engines, they are more prone to damage  from cooling stress. Gradual reductions in power and careful  monitoring of temperatures are essential in the descent  phase. Extending the landing gear during the descent may  help control the airspeed while maintaining a higher engine  power setting. This allows the pilot to reduce power in small  increments which allows the engine to cool slowly. It may  also be necessary to lean the mixture slightly to eliminate  roughness at the lower power settings. Turbocharged engines must be thoughtfully and carefully  operated with continuous monitoring of pressures and  temperatures. There are two temperatures that are especially  important—turbine inlet temperature (TIT) or, in some  installations, exhaust gas temperature (EGT) and cylinder  head temperature. TIT or EGT limits are set to protect the  elements in the hot section of the turbocharger, while cylinder  head temperature limits protect the engine’s internal parts. Due to the heat of compression of the induction air, a  turbocharged engine runs at higher operating temperatures  than a non-turbocharged engine. Because turbocharged  engines operate at high altitudes; their environment is less  efficient for cooling. At altitude, the air is less dense and,  therefore, cools less efficiently. Also, the less dense air causes  the compressor to work harder. Compressor turbine speeds  can reach 80,000–100,000 rpm, adding to the overall engine  operating temperatures. Turbocharged engines are also  operated at higher power settings a greater portion of the time. Because of the high temperatures and pressures produced  in the turbine exhaust systems, any malfunction of the  turbocharger must be treated with extreme caution. In  all cases of turbocharger operation, the manufacturer’s  recommended procedures should be followed. This is  especially so in the case of turbocharger malfunction.  However, in those instances where the manufacturer’s  procedures do not adequately describe the actions to be  taken in the event of a turbocharger failure, the following  procedures should be used. If an excessive rise in manifold pressure occurs during  normal advancement of the throttle (possibly owing to faulty  operation of the waste gate):  High heat is detrimental to piston engine operation. Its  cumulative effects can lead to piston, ring, and cylinder  head failure and place thermal stress on other operating  components. Excessive cylinder head temperature can lead to  11-10 • Immediately retard the throttle smoothly to limit the  manifold pressure below the maximum for the rpm  and mixture setting Heat Management Turbocharger Failure Over-Boost Condition