These engines, sometimes referred to as sea level-boosted  engines, can develop more power at sea level than an engine  without turbosupercharging. As was mentioned earlier, an  engine must be boosted above 30 "Hg to truly be supercharged.  This type of turbocharger accomplishes this by increasing the  manifold pressure above 30 "Hg to around 40 "Hg.  directed, strike the turbine blades, arranged radially around  the outer edge of the turbine, and cause the rotor (turbine and  impeller) to rotate. The gases, having exhausted most of their  energy, are then exhausted overboard. When the waste gate  is fully open, nearly all of the exhaust gases pass overboard  providing little or no boost. Some engines used in light aircraft are equipped with an  externally driven normalizing system. These systems are  powered by the energy of exhaust gases and are usually referred  to as “normalizing turbocharger” systems. These systems were  not designed to be used as a true supercharger (boost manifold  pressure over 30 "Hg). They compensate for the power lost due  to the pressure drop resulting from increased altitude. On many  small aircraft engines, the turbocharger (normalizing) system  is designed to be operated only above a certain altitude, 5,000  feet for example, since maximum power without normalizing is  available below that altitude. The location of the air induction  and exhaust systems of a typical normalizing turbocharger  system for a small aircraft is shown in  Figure 3-16. The turbosupercharger air induction system consists of a  filtered ram-air intake located on the side of the nacelle.  [Figure 3-17]  An alternate air door within the nacelle  permits compressor suction automatically to admit alternate  air (heated engine compartment air) if the induction air filter  becomes clogged. In many cases, the alternate air door can  be operated manually in the event of filter clogging.  Normalizer Turbocharger Some ground-boosted (sea level) turbosupercharged systems  are designed to operate from sea level up to their critical altitude.  Almost all turbocharger systems use engine oil as the control  fluid for controlling the amount of boost (extra manifold  pressure) provided to the engine. The waste-gate actuator and  controllers use pressurized engine oil for their power supply.  The turbocharger is controlled by the waste gate and waste  gate actuator. The waste gate actuator, which is physically  connected to the waste gate by mechanical linkage, controls  the position of the waste gate butterfly valve. The waste gate  bypasses the engine exhaust gases around the turbocharger  turbine inlet. By controlling the amount of exhaust gases that pass through the turbine of the turbocharger, the speed  Ground-Boosted Turbosupercharger System Intake manifold Throttle and mixture control Air intake Alternate air intake Turbocharger Control system Exhaust system Induction system Figure 3-16.  Typical location of the air induction and exhaust systems of a normalizing turbocharger system.  3-11