Fan assembly for a gas turbine engine

A gas turbine engine comprising:

• a compressor section;
• a combustor;
• a turbine section;
• and
• a fan assembly, the fan assembly defining a fan assembly centerline axis, the fan assembly comprising (a) a fan actuation system, (b) a fan blade hub, (c) a plurality of fan blades, each fan blade being rotationally connected to the fan blade hub and connected to the fan actuation system, the fan actuation system being arranged to rotate about a respective blade pitch change axis, and (d) a counterweight system arranged disconnected from the plurality of fan blades and being connected to the fan actuation system, the counterweight system including (i) a counterweight hub and (ii) a plurality of counterweight levers, each of the counterweight levers having (1) a counterweight trunnion portion rotationally connected to the counterweight hub and connected to the fan actuation system that rotates each counterweight lever about a respective counterweight lever rotational axis extending through the counterweight trunnion portion and extending radially from the fan assembly centerline axis, (2) a cantilever arm having a first end connected to the counterweight trunnion portion and a second end offset from the respective counterweight lever rotational axis, and (3) a counterweight connected to the second end, the counterweight having a counterweight center-of-gravity,
• wherein the fan actuation system is arranged to correspondingly rotate each of the plurality of fan blades and each of the plurality of counterweight levers in unison.

A method of operating a gas turbine engine, the gas turbine engine comprising (1) a compressor section, (2) a combustor, (3) a turbine section, and (4) a fan assembly, the fan assembly defining a fan assembly centerline axis about which the fan assembly rotates when the fan assembly is driven by the turbine section, the fan assembly comprising (a) a fan actuation system comprising a blade-counterweight actuator assembly, (b) a fan blade hub, (c) a plurality of fan blades, each fan blade being rotationally connected to the fan blade hub and connected to the fan actuation system, the fan actuation system being arranged to rotate about a respective blade pitch change axis, and (d) a counterweight system arranged disconnected from the plurality of fan blades and being connected to the fan actuation system, the counterweight system including (i) a counterweight hub and (ii) a plurality of counterweight levers, each of the counterweight levers having (1) a counterweight trunnion portion rotationally connected to the counterweight hub and connected to the blade-counterweight actuator assembly that rotates each counterweight lever about a respective counterweight lever rotational axis extending through the counterweight trunnion portion and extending radially from the fan assembly centerline axis, (2) a cantilever arm having a first end connected to the counterweight trunnion portion and a second end offset from the respective counterweight lever rotational axis, and (3) a counterweight connected to the second end, the counterweight having a counterweight center-of-gravity, the method comprising:

• operating the blade-counterweight actuator assembly, in unison, (A) to rotate the plurality of fan blades to be arranged in a first blade rotational position with respect to the respective blade pitch change axis, and, (B) to rotate the plurality of counterweight levers to be arranged in a first lever rotational position with respect to the respective counterweight lever rotational axis;
• operating the compressor section, the combustor, and the turbine section to cause the turbine section to rotate and to drive rotation of the fan assembly about the fan assembly centerline axis;
• and
• operating the blade-counterweight actuator assembly, in unison, (C) to rotate the plurality of fan blades to be arranged in a second blade rotational position with respect to the blade pitch change axis, and (D) to rotate the plurality of counterweight levers to be arranged in a second lever rotational position with respect to the respective counterweight lever rotational axis, the second blade rotational position imparting a torque by each fan blade about the respective blade pitch change axis, and imparting a first blade axial force by each fan blade to the blade-counterweight actuator assembly, and, the second lever rotational position imparting a torque by each counterweight about the respective counterweight lever rotational axis, and imparting a first counterweight axial force by each counterweight lever to the blade-counterweight actuator assembly, the first counterweight axial force opposing the first blade axial force.