An actuator system for controlling an aerodynamic control surface of an aircraft, the system comprising: a first actuator receiving a first actuator input and a first linear translation element that moves based on the first actuator input, the first linear translation element operably connected to a first portion of the aerodynamic control surface to move the first portion of the aerodynamic control surface; a first sensor assembly disposed relative to the first actuator that generates a first sensor output based on a displacement of the first linear translation element; a second actuator receiving a second actuator input and a second linear translation element that moves based on the second actuator input, the second linear translation element operably connected to a second portion of the aerodynamic control surface to move the second portion of the aerodynamic control surface; a second sensor assembly disposed relative to the second actuator that generates a second sensor output based on a displacement of the second linear translation element; and a controller that generates the first and second actuator inputs and receives the first and second sensor outputs and determines if an error condition exists for the system based on the first and second sensor outputs; wherein the first linear translation element is a threaded ball screw shaft that is driven by a ball nut, wherein the first sensor assembly comprises a first optical sensor and a second optical sensor, wherein the first and second optical sensors are positioned relative to the first linear translation element to detect the threads of the first linear translation element, wherein the first and second optical sensors are positioned with a circumferential offset relative to the first linear translation element. a first actuator receiving a first actuator input and a first linear translation element that moves based on the first actuator input, the first linear translation element operably connected to a first portion of the aerodynamic control surface to move the first portion of the aerodynamic control surface; a first sensor assembly disposed relative to the first actuator that generates a first sensor output based on a displacement of the first linear translation element; a second actuator receiving a second actuator input and a second linear translation element that moves based on the second actuator input, the second linear translation element operably connected to a second portion of the aerodynamic control surface to move the second portion of the aerodynamic control surface; a second sensor assembly disposed relative to the second actuator that generates a second sensor output based on a displacement of the second linear translation element; and a controller that generates the first and second actuator inputs and receives the first and second sensor outputs and determines if an error condition exists for the system based on the first and second sensor outputs; wherein the first linear translation element is a threaded ball screw shaft that is driven by a ball nut, wherein the first sensor assembly comprises a first optical sensor and a second optical sensor, wherein the first and second optical sensors are positioned relative to the first linear translation element to detect the threads of the first linear translation element, wherein the first and second optical sensors are positioned with a circumferential offset relative to the first linear translation element. <EOS>