Flutter sensing and control system for a gas turbine engine

Abstract

An exemplary gas turbine engine assembly includes a nacelle, a core engine casing within the nacelle, a low pressure turbine having a pressure ratio that is greater than five, and a bypass passage established between the nacelle and the core engine casing. About 80% or more of airflow entering the engine is moved through the bypass passage.

1 . A gas turbine engine assembly, comprising:
 a nacelle;   a core engine casing within the nacelle;   a low pressure turbine having a pressure ratio that is greater than five; and   a bypass passage established between the nacelle and the core engine casing, wherein about 80% or more of airflow entering the engine is moved through the bypass passage.   
     
     
         2 . The gas turbine engine assembly of  claim 1 , wherein about 80% of the airflow entering the engine is moved through the bypass passage. 
     
     
         3 . The gas turbine engine assembly of  claim 1 , including a fan and a gear train, wherein the gear train reduces the rotational speed of the fan relative to a shaft of the gas turbine engine, the shaft rotatably coupled to a low pressure compressor of the engine. 
     
     
         4 . The gas turbine engine assembly of  claim 3 , wherein the gear train is a planetary gear train. 
     
     
         5 . The gas turbine engine assembly of  claim 1 , including a variable area fan nozzle that controls a discharge airflow area of the bypass passage. 
     
     
         6 . The system as recited in  claim 5 , wherein the discharge airflow area extends between the variable area fan nozzle and the core engine casing. 
     
     
         7 . The gas turbine engine assembly of  claim 6 , including a controller that is operable to move the variable area fan nozzle to change the discharge airflow area associated with the variable area fan nozzle in response to an airfoil flutter condition. 
     
     
         8 . The gas turbine engine assembly of  claim 7 , wherein the controller influences the discharge airflow area by moving the variable area fan nozzle between a first position having a first discharge airflow area and a second position having a second discharge airflow area greater than the first discharge airflow area in response to the airfoil flutter condition. 
     
     
         9 . A gas turbine engine assembly, comprising:
 a nacelle;   a core engine casing within the nacelle;   a low pressure turbine having a pressure ratio that is greater than five; and   a bypass passage established between the nacelle and the core engine casing, wherein a ratio of an amount of airflow communicated through the bypass passage to an amount of airflow communicated through the core engine is greater than  10 .   
     
     
         10 . The gas turbine engine assembly of  claim 9 , including a fan and a gear train, wherein the gear train reduces the rotational speed of the fan relative to a shaft of the gas turbine engine, the shaft rotatably coupled to a low pressure compressor of the engine. 
     
     
         11 . The gas turbine engine assembly of  claim 10 , wherein the gear train is a planetary gear train. 
     
     
         12 . The gas turbine engine assembly of  claim 9 , including a variable area fan nozzle that controls a discharge airflow area of the bypass passage. 
     
     
         13 . The gas turbine engine assembly of  claim 12 , wherein the discharge airflow area extends between the variable area fan nozzle and the core engine casing. 
     
     
         14 . The gas turbine engine assembly of  claim 12 , including
 a controller that is operable to move the variable area fan nozzle to change the discharge airflow area associated with the variable area fan nozzle in response to the airfoil flutter condition.   
     
     
         15 . The gas turbine engine assembly of  claim 14 , wherein the controller influences the discharge airflow area by moving the variable area fan nozzle between a first position having a first discharge airflow area and a second position having a second discharge airflow area greater than the first discharge airflow area in response to detection of the airfoil flutter condition.