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A turboprop engine having a variable pitch propeller driven through a speed reducing transmission. The engine has a compressor section with a low pressure component and a high pressure component. A flow control device is positioned between the low and high pressure components. During takeoff, air fr

A turboprop engine having a variable pitch propeller driven through a speed reducing transmission. The engine has a compressor section with a low pressure component and a high pressure component. A flow control device is positioned between the low and high pressure components. During takeoff, air from the low pressure component is bypassed, and during cruise, the air from the low pressure component is passed directly through the high pressure component, thus obtaining improved matching of engine components for both takeoff and cruise.

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A turboprop engine comprising: (a) a compressor having a low pressure compressor component and a high pressure compressor component; (b) a turbine operatively connected through drive means to said compressor; (c) a combustion section arranged to receive air flow from the compressor and burn fuel the

A turboprop engine comprising: (a) a compressor having a low pressure compressor component and a high pressure compressor component; (b) a turbine operatively connected through drive means to said compressor; (c) a combustion section arranged to receive air flow from the compressor and burn fuel therein to provide a gaseous flow to drive the turbine; (d) a variable pitch propeller rotatably mounted and positioned to react against ambient air to produce a thrust; (e) a speed reducing transmission operatively connected between said turbine and said propeller to drive said propeller at a reduced rotational speed relative to the turbine; (f) air inlet means to direct air flow into said engine; (g) air inlet bypass means arranged to provide a bypass inlet air flow that bypasses said low pressure compressor component; (h) air outlet bypass duct means arranged to provide air flow that bypasses the high pressure compressor component, combustion section, and the turbine; (i) flow control means operatively positioned to receive air flow from said air inlet bypass means and air flow from said low pressure compressor component, and to direct air flow to said air outlet bypass duct means and air flow to said high pressure compressor component, said flow control means having a first position where air flow from said air inlet bypass means is directed to said high pressure compressor component and air flow from said low pressure compressor component is directed to said air outlet bypass duct means, and a second position where air flow from the air inlet bypass duct means is directed to the air outlet bypass duct means and air from the low pressure compressor component is directed to the high pressure compressor component. A method of operating a turboprop engine, wherein said engine comprises: (a) a compressor having a low pressure compressor component and a high pressure compressor component; (b) a turbine operatively connected through drive means to said compressor; (c) a combustion section arranged to receive airflow from the compressor and burn fuel therein to provide a gaseous flow to drive the turbine; (d) a variable pitch propeller rotatably mounted and positioned to react against ambient air to produce a thrust; (e) a speed reducing transmission operatively connected between said turbine and said propeller to drive said propeller at a reduced rotational speed relative to the turbine; (f) air inlet means to direct airflow into said engine; (g) air inlet bypass means arranged to provide a bypass inlet airflow that bypasses said low pressure compressor component; (h) air outlet bypass duct means arranged to provide airflow that bypasses the high pressure compressor component, combustion section, and the turbine; said method comprising: (a) receiving airflow from said air inlet bypass means and airflow from said low pressure compressor component, and directing airflow through flow control means to said air outlet bypass duct means and airflow to said high pressure compressor component; (b) during take-off mode directing airflow from said air inlet bypass means to said high pressure compressor component and airflow from said low pressure compressor component to said air outlet bypass duct means; (c) during cruise mode directing airflow from the air inlet bypass duct means to the air outlet bypass duct means and air from the low pressure compressor component to the high pressure compressor component.