Secondary systems and methods of control for variable area fan nozzles

An aircraft, comprising:

• a gas turbine engine;
• a variable area fan nozzle (VAFN) mounted to a downstream end of the gas turbine engine, the VAFN including a plurality of petals and at least one actuator configured to move the plurality of petals;
• and
• a control system in operative communication with the gas turbine engine and the VAFN, the control system including:
• at least one pressure sensor configured to determine a backpressure of the gas turbine engine;
• at least one strain sensor configured to determine a fan blade strain of the gas turbine engine;
• and
• a control module in operative communication with the at least one pressure sensor, the at least one strain sensor, and a primary system configured to configured to acquire primary data indicative of an operating condition of the VAFN, the control module configured to:
• calculate a real-time nozzle area of the VAFN based at least in part on the primary data,
• generate an actuator command based at least in part on the real-time nozzle area and a predetermined table of nozzle areas preprogrammed into a memory of the control module,
• modify the actuator command based on at least one of the determined backpressure and the determined fan blade strain, and
• send the modified actuator command to the at least one actuator of the VAFN to adjust the plurality of petals.

A method for controlling a nozzle area of a variable area fan nozzle (VAFN) having a plurality of petals, the VAFN for use with a gas turbine engine, the method comprising:

• acquiring primary data indicative of an operating condition of the VAFN;
• acquiring secondary data indicative of a backpressure and a fan blade strain of the gas turbine engine;
• calculating the nozzle area of the VAFN based on the primary data;
• generating a desired nozzle area based at least in part on a predetermined table of nozzle areas;
• producing an actuator command based on a difference between the calculated nozzle area and the desired nozzle area;
• adjusting the actuator command based on the secondary data;
• and
• sending the adjusted actuator command to the VAFN to move the plurality of petals, the calculating, generating, producing, adjusting, and sending being performed by a control module associated with the VAFN and the gas turbine engine.