AHRS is an important system that provides the 3-dimensional orientation (roll, pitch and yaw or heading) of an aircraft from which the flying performance can be evaluated. The avionics of aircraft are very sophisticated and majority of them do not allow any external interface for logging. As such, a standalone external AHRS is needed which should be comprised of low cost devices so that it becomes affordable for other aircrafts. This paper proposes a low cost Micro-Electrical-Mechanical system (MEMS) based AHRS for low speed aircraft to evaluate the flying performance. MEMS based 3-axis accelerometer, gyroscope and magnetometer have been used to build the AHRS. Low cost MEMS based sensors suffer from bias, drift and sudden spike. Low pass filter has been utilized to reduce the spikes. Complementary filter has been used to pin down the drift of the gyroscope from accelerometer reading. The system has been implemented in Arduino environment. Simulation and real time results have shown correct functioning of the system. Besides using as an AHRS in low speed aircraft, the system can be used for control and stabilization of other real time system.