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sensitive to the throttle differential pressure than to deck pressure, thereby accomplishing deck pressure reduction as the throttle is closed. 

## Absolute Pressure Controller 

One device used to control the speed and output of the turbocharger, but controls the system only at maximum output, is the absolute pressure controller. The absolute pressure controller contains an aneroid bellows that is referenced to upper deck pressure. It operates the wastegate, which diverts, more or less, exhaust gas over the turbine. As an absolute pressure setting is reached, it bypasses oil, and relieves the pressure on the waste gate actuator. This allows the absolute pressure controller to control the maximum turbocharger compressor discharge pressure. The turbocharger is completely automatic, requiring no pilot action up to the critical altitude. 

## Turbocharger System Troubleshooting 

Figure 3-23  includes some of the most common turbocharger system malfunctions together with their cause and repair. These troubleshooting procedures are presented as a 

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guide only and should not be substituted for applicable manufacturer’s instructions or troubleshooting procedures. 

## Turbine Engine Inlet Systems 

The engine inlet of a turbine engine is designed to provide a relatively distortion-free flow of air, in the required quantity, to the inlet of the compressor. [Figure 3-24]  Many engines use inlet guide vanes (IGV) to help straighten the airflow and direct it into the first stages of the compressor. A uniform and steady airflow is necessary to avoid compressor stall (airflow tends to stop or reverse direction of flow) and excessive internal engine temperatures in the turbine section. Normally, the air-inlet duct is considered an airframe part and not a part of the engine. However, the duct is very important to the engine’s overall performance and the engine’s ability to produce an optimum amount of thrust. 

A gas turbine engine consumes considerable more airflow than a reciprocating engine. The air entrance passage is correspondingly larger. Furthermore, it is more critical in determining engine and aircraft performance, especially at high airspeeds. Inefficiencies of the inlet duct result in successively magnified losses through other components of 

