This paper describes, the development of a sensor fusion algorithm-based Kalman filter architecture, in combination with a low cost Inertial Measurement Unit (IMU) for an Attitude Heading Reference System (AHRS). A low cost IMU takes advantage of the use of MEMS technology enabling cheap, compact, low grade sensors. The use of low cost IMUs is primarily targeted towards Unmanned Aerial Vehicle (UAV) applications due to the requirements for small package size, light weight, and low energy consumption. The high dynamics nature of smaller airframes, coupled with the typical vibration induced noise of UAVs require an efficient, reliable, and robust AHRS for vehicle control. To eliminate the singularities at ±90 • on the pitch and roll axes, and to keep the computational efficiency high, quaternions are used for state attitude representation. x