Flexible support structure for a geared architecture gas turbine engine

Abstract

A gas turbine engine includes a fan that has fan blades. A fan shaft is drivingly connected to the fan. A frame supports the fan shaft and defines a frame lateral stiffness. A gear system is connected to the fan shaft and driven through an input. A gear system flex mount arrangement accommodates misalignment of the fan shaft and the input during operation and includes a flexible support that defines a flexible support lateral stiffness that is less than 11% of the frame lateral stiffness.

1 . A gas turbine engine, comprising:
 a fan having fan blades;   a fan shaft drivingly connected to said fan;   a frame supporting said fan shaft and defining a frame lateral stiffness;   a gear system connected to said fan shaft and driven through an input; and   a gear system flex mount arrangement, wherein said flex mount arrangement accommodates misalignment of said fan shaft and said input during operation and includes a flexible support defining a flexible support lateral stiffness that is less than 11% of said frame lateral stiffness.   
     
     
         2 . The gas turbine engine of  claim 1 , wherein said gear system includes a gear mesh defining a gear mesh lateral stiffness and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness. 
     
     
         3 . The gas turbine engine of  claim 2 , wherein said gear system includes a ring gear defining a ring gear lateral stiffness that is less than 12% of said gear mesh lateral stiffness. 
     
     
         4 . The gas turbine engine of  claim 3 , further comprising a gear reduction ratio of greater than 2.3, a bypass ratio greater than ten (10), a fan pressure ratio of less than 1.45 measured across said fan blades alone, and a low pressure turbine with an inlet, an outlet, and a low pressure turbine pressure ratio greater than 5:1, wherein said low pressure turbine pressure ratio is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet prior to any exhaust nozzle. 
     
     
         5 . The gas turbine engine of  claim 4 , wherein said flexible support defines a flexible support transverse stiffness, said gear mesh defines a gear mesh transverse stiffness, and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. 
     
     
         6 . The gas turbine engine of  claim 5 , wherein said ring gear defines a ring gear transverse stiffness and said ring gear transverse stiffness is less than 12% of said gear mesh transverse stiffness. 
     
     
         7 . The gas turbine engine of  claim 6 , further comprising a two stage high pressure turbine. 
     
     
         8 . The gas turbine engine of  claim 7 , further comprising a three stage low pressure compressor. 
     
     
         9 . The gas turbine engine of  claim 7 , further comprising a fan tip speed of less than 1150 ft/second. 
     
     
         10 . The gas turbine engine of  claim 3 , wherein said input to said gear system defines an input lateral stiffness and said input lateral stiffness is less than 11% of said frame lateral stiffness. 
     
     
         11 . The gas turbine engine of  claim 10 , wherein said input lateral stiffness is less than 5% of said gear mesh lateral stiffness. 
     
     
         12 . The gas turbine engine of  claim 11 , further comprising a journal bearing defining a journal bearing lateral stiffness that is less than said gear mesh lateral stiffness. 
     
     
         13 . The gas turbine engine of  claim 10 , wherein said ring gear defines a ring gear transverse stiffness, said gear mesh defines a gear mesh transverse stiffness, said flexible support defines a flexible support transverse stiffness, said ring gear transverse stiffness is less than 12% of said gear mesh transverse stiffness, and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. 
     
     
         14 . A gas turbine engine, comprising:
 a fan having fan blades;   a fan shaft drivingly connected to said fan;   a frame supporting said fan shaft and defining a frame lateral stiffness;   a gear system connected to said fan shaft and driven through an input to said gear system;   a gear system flex mount arrangement, wherein said flex mount arrangement accommodates misalignment of said fan shaft and said input during operation, and includes a flexible support defining a flexible support lateral stiffness that is less than 11% of said frame lateral stiffness; and   a two stage high pressure turbine.   
     
     
         15 . The gas turbine engine of  claim 14 , further comprising a gear reduction ratio of greater than 2.3, a bypass ratio greater than ten (10), a fan pressure ratio of less than 1.45 measured across said fan blades alone, and a low pressure turbine with an inlet, an outlet, and a low pressure turbine pressure ratio greater than 5:1, wherein said low pressure turbine pressure ratio is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet prior to any exhaust nozzle. 
     
     
         16 . The gas turbine engine of  claim 15 , further comprising a fan tip speed of less than 1150 ft/second. 
     
     
         17 . The gas turbine engine of  claim 15 , further comprising a gear mesh defining a gear mesh lateral stiffness and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness. 
     
     
         18 . The gas turbine engine of  claim 15 , further comprising a gear mesh defining a gear mesh lateral stiffness, a ring gear defining a ring gear lateral stiffness, and said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness. 
     
     
         19 . The gas turbine engine of  claim 18 , wherein said ring gear defines a ring gear transverse stiffness, said gear mesh defines a gear mesh transverse stiffness, said flexible support defines a flexible support transverse stiffness, said ring gear transverse stiffness is less than 12% of said gear mesh transverse stiffness and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. 
     
     
         20 . The gas turbine engine of  claim 15 , wherein said input defines an input lateral stiffness and said input lateral stiffness is less than 11% of said frame lateral stiffness. 
     
     
         21 . The gas turbine engine of  claim 20 , further comprising a gear mesh defining a gear mesh lateral stiffness and said input lateral stiffness is less than 5% of said gear mesh lateral stiffness. 
     
     
         22 . The gas turbine engine of  claim 21 , further comprising further comprising a fan tip speed of less than 1150 ft/second. 
     
     
         23 . A gas turbine engine, comprising:
 a fan having fan blades;   a fan shaft driving said fan in operation;   a frame supporting said fan shaft and defining a frame lateral stiffness;   a gear system connected to said fan shaft and driven through an input to said gear system, the gear system including a ring gear defining a ring gear lateral stiffness;   a gear system flex mount arrangement, wherein said flex mount arrangement accommodates misalignment of said fan shaft and said input during operation, and includes a gear mesh defining a gear mesh lateral stiffness and a flexible support defining a flexible support lateral stiffness that is less than 11% of said frame lateral stiffness; and   wherein said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness.   
     
     
         24 . The gas turbine engine of  claim 23 , further comprising a two stage high pressure turbine. 
     
     
         25 . The gas turbine engine of  claim 24 , wherein said flexible support defines a flexible support transverse stiffness, said frame defines a frame transverse stiffness, said flexible support transverse stiffness is less than 11% of said frame transverse stiffness. 
     
     
         26 . The gas turbine engine of  claim 25 , wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness. 
     
     
         27 . The gas turbine engine of  claim 26 , further comprising a gear reduction ratio of greater than 2.3, a bypass ratio greater than ten (10), a fan pressure ratio of less than 1.45 measured across said fan blades alone, and a low pressure turbine with an inlet, an outlet, and a low pressure turbine pressure ratio greater than 5:1, wherein said low pressure turbine pressure ratio is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet prior to any exhaust nozzle. 
     
     
         28 . The gas turbine engine of  claim 27 , wherein said ring gear defines a ring gear transverse stiffness, said gear mesh defines a gear mesh transverse stiffness, said ring gear transverse stiffness is less than 12% of said gear mesh transverse stiffness, and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. 
     
     
         29 . The gas turbine engine of  claim 28 , further comprising a fan tip speed of less than 1150 ft/second. 
     
     
         30 . The gas turbine engine of  claim 29 , wherein said input defines an input lateral stiffness, wherein said input lateral stiffness is less than 11% of said frame lateral stiffness and less than 5% of said gear mesh lateral stiffness.