AHARS or AHRS is an abbreviation for Attitude and Heading Reference System. An AHARS/AHRS unit normally consists of solid-sate sensors that provide attitude, heading, roll, pitch, and yaw for an aircraft. AHARS/AHRS was designed to replace legacy mechanical gyroscopic flight instruments due to higher reliability.  AHARS/AHRS may be combined with an air data computer to produce ADAHRS to provide other data such as airspeed, altitude and OAT (outside air temperature).