Flexible support structure for a geared architecture gas turbine engine

A gas turbine engine, comprising:

• a fan having fan blades;
• an outer housing surrounding the fan, and a bypass flow path within said outer housing;
• a fan shaft drivingly connected to said fan;
• a frame supporting said fan shaft and defining a frame lateral stiffness and a frame transverse stiffness;
• a gear system connected to said fan shaft and driven through an input defining an input lateral stiffness and an input transverse stiffness, said gear system includes a gear mesh defining a gear mesh lateral stiffness and a gear mesh transverse stiffness;
• and
• a gear system flex mount arrangement, wherein said gear system flex mount arrangement accommodates misalignment of said fan shaft and said input during operation and includes a flexible support which supports said gear system relative to a static structure and defines 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;
• and
• wherein at least one of said input lateral stiffness and said input transverse stiffness is less than 11% of a respective one of said frame lateral stiffness and said frame transverse stiffness.