Rotary servo for fixed fail actuators

A method comprising:

• receiving a control signal;
• and
• rotating, by a stepper motor of a servo assembly and based on the control signal, a cylindrical outer spool within a cylindrical outer sleeve in which the cylindrical outer spool is annularly displaced within to deliver a fluid to and thereby actuate an actuator to control compressor variable geometry of a gas turbine engine,
• wherein the cylindrical outer sleeve includes multiple ports,
• wherein the stepper motor is mechanically coupled to the cylindrical outer spool,
• wherein the cylindrical outer spool includes multiple channels configured to provide fluidic interconnection between the multiple ports and a cylindrical inner spool,
• wherein the cylindrical inner spool is annularly displaced within the cylindrical outer spool, the cylindrical inner spool including grooves configured to provide fluidic interconnection through the multiple channels of the cylindrical outer sleeve, and
• wherein the actuator is mechanically coupled to the compressor variable geometry.

A gas turbine engine comprising:

• a combustor;
• a compressor fluidically upstream of the combustor that includes compressor variable geometry configured to control compression by the compressor;
• and
• a rotary actuation system mounted to a body of the gas turbine engine, the rotary actuation system including:
• a servo assembly that includes:
• a cylindrical outer sleeve including multiple ports;
• a stepper motor mechanically coupled to a cylindrical outer spool annularly displaced within the cylindrical outer sleeve;
• the cylindrical outer spool including multiple channels configured to provide fluidic interconnection between the multiple ports and a cylindrical inner spool;
• and
• the cylindrical inner spool annularly displaced within the cylindrical outer spool, the cylindrical inner spool including grooves configured to provide fluidic interconnection through the multiple channels of the cylindrical outer sleeve;
• and
• an actuator mechanically coupled to the compressor variable geometry,
• wherein the stepper motor is configured to rotate the cylindrical outer spool within the cylindrical sleeve to deliver a fluid to and thereby actuate the actuator to control the compressor variable geometry.