Geared architecture for high speed and small volume fan drive turbine

Abstract

A gas turbine engine according to an example of the present disclosure includes, among other things, a fan shaft drivingly connected to a fan with the fan having fan blades. A fan shaft support that supports the fan shaft and a gear system drivingly connected to the fan shaft. The gear system includes a ring gear defining a ring gear lateral stiffness and a ring gear transverse stiffness, a gear mesh defining a gear mesh lateral stiffness and a gear mesh transverse stiffness, and a reduction ratio greater than 2.3. At least one of the ring gear lateral stiffness and said ring gear transverse stiffness is less than 12% of a respective one of the gear mesh lateral stiffness and the gear mesh transverse stiffness.

What is claimed is: 
     
         1 . A gas turbine engine, comprising:
 a fan shaft drivingly connected to a fan, said fan having fan blades;   a fan shaft support that supports said fan shaft;   a gear system drivingly connected to said fan shaft, said gear system includes a ring gear defining a ring gear lateral stiffness and a ring gear transverse stiffness, a gear mesh defining gear mesh lateral stiffness and a gear mesh transverse stiffness, and a reduction ratio greater than 2.3; and   wherein at least one of said ring gear lateral stiffness and said ring gear transverse stiffness is less than 12% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.   
     
     
         2 . The gas turbine engine of  claim 1 , further comprising a flexible support defining a flexible support lateral stiffness and a flexible support transverse stiffness, wherein at least one of said flexible support lateral stiffness and said flexible support transverse stiffness is less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness. 
     
     
         3 . The gas turbine engine of  claim 2 , wherein said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. 
     
     
         4 . The gas turbine engine of  claim 3 , wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness. 
     
     
         5 . The gas turbine engine of  claim 3 , further comprising a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across the fan blades alone. 
     
     
         6 . The gas turbine engine of  claim 5 , further comprising 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. 
     
     
         7 . The gas turbine engine of  claim 6 , further comprising a bypass ratio greater than ten (10). 
     
     
         8 . The gas turbine engine of  claim 7 , further comprising a fan tip speed less than about 1150 ft/second. 
     
     
         9 . The gas turbine engine of  claim 7 , further comprising a mid-turbine frame including at least one airfoil extending into a flow path. 
     
     
         10 . The gas turbine engine of  claim 9 , further comprising fan bearings supporting said fan shaft, wherein the gear system is located aft of said fan bearings and the gear system is a planetary gear system. 
     
     
         11 . The gas turbine engine of  claim 7 , wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness. 
     
     
         12 . The gas turbine engine of  claim 2 , wherein said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. 
     
     
         13 . The gas turbine engine of  claim 1 , further comprising a flexible support defining a flexible support lateral stiffness and a flexible support transverse stiffness, wherein said fan shaft support defines a fan shaft support lateral stiffness and a fan shaft support transverse stiffness and at least one of said flexible support lateral stiffness and said flexible support transverse stiffness is less than 11% of a respective one of said fan shaft support lateral stiffness and said fan shaft support lateral stiffness. 
     
     
         14 . The gas turbine engine of  claim 13 , wherein said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness. 
     
     
         15 . The gas turbine engine of  claim 13 , further comprising a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across the fan blades alone. 
     
     
         16 . The gas turbine engine of  claim 15 , further comprising 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. 
     
     
         17 . The gas turbine engine of  claim 15 , further comprising a bypass ratio greater than ten (10). 
     
     
         18 . The gas turbine engine of  claim 17 , further comprising a fan tip speed less than about 1150 ft/second. 
     
     
         19 . The gas turbine engine of  claim 17 , further comprising a mid-turbine frame including at least one airfoil extending into a flow path. 
     
     
         20 . The gas turbine engine of  claim 17 , wherein the flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness. 
     
     
         21 . The gas turbine engine of  claim 17 , wherein the flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness. 
     
     
         22 . The gas turbine engine of  claim 21 , wherein at least one of said flexible support lateral stiffness and said flexible support transverse stiffness is less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness. 
     
     
         23 . The gas turbine engine of  claim 22 , wherein said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness. 
     
     
         24 . The gas turbine engine of  claim 23 , further comprising a fan tip speed less than about 1150 ft/second. 
     
     
         25 . The gas turbine engine of  claim 13 , wherein said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness. 
     
     
         26 . The gas turbine engine of  claim 25 , wherein said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness. 
     
     
         27 . The gas turbine engine of  claim 26 , further comprising a two stage high pressure turbine. 
     
     
         28 . The gas turbine engine of  claim 27 , further comprising a low fan pressure ratio of less than 1.45 wherein said low fan pressure ratio is measured across the fan blades alone. 
     
     
         29 . The gas turbine engine of  claim 28 , wherein at least one of said flexible support lateral stiffness and said flexible support transverse stiffness is less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness. 
     
     
         30 . The gas turbine engine of  claim 29 , further comprising a fan tip speed less than about 1150 ft/second.