Mounting assembly for a gearbox assembly

A gas turbine engine comprising:

• a fan and a turbine section having a rotating shaft drivingly coupled to the fan;
• an engine static structure;
• a gearbox assembly configured to transfer rotational energy from the turbine section to the fan;
• and
• a mounting assembly for coupling the gearbox assembly to the gas turbine engine, the mounting assembly having:
• a flex coupling configured to mount a first gear of the gearbox assembly to the rotating shaft, the first gear being a split sun gear comprising a forward sun gear and an aft sun gear separate from the forward sun gear, wherein the forward sun gear and the aft sun gear are each rotationally coupled to the rotating shaft;
• a flex mount configured to mount a second gear of the gearbox assembly to an engine static structure;
• and
• a fan frame configured to mount a third gear of the gearbox assembly to the engine static structure,
• wherein each of the flex coupling and the flex mount is characterized by a lateral impedance parameter ratio, a bending impedance parameter ratio, and a torsional impedance parameter ratio,
• wherein the lateral impedance parameter ratio of the flex coupling, the flex mount, or both is less than or equal to 0.5,
• wherein the bending impedance parameter ratio of the flex coupling, the flex mount, or both is less than or equal to 0.5, and
• wherein the torsional impedance parameter ratio of the flex coupling, the flex mount, or both is greater than or equal to 0.1.