since 1940

Aircraft Maintenance TroubleShoot > Aircraft Turbocharger & Controller

Cessna 401B 70-72

2. Turbos mounted above engine power settings from sea level to altitude. The controller senses deck pressure, compares it to a reference absolute pressure, adjusts the wastegate butterfly (controlling turbo speed) to maintain sea-level horsepower at varying altitudes.

The pressure ratio controller portion of the dual controller is designed to override the fixed absolute pressure controller during high-altitude cruising to prevent turbocharger overspeed and lower the part-throttle critical power point of the engine. The controller senses deck and ambient pressures and compares them to a referenced absolute pressure. When the ratio of outlet to ambient pressure exceeds a preset proportion, the controller opens the wastegate and lowers turbo output.

If fitted, a pressure relief valve, set slightly in excess of maximum deck pressure is provided to prevent damaging overboost in the event of a system malfunction.

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