check this "For the inertial guidance system, ACAL recommended a Bosch BMA150 3-axis accelerometer which works in conjunction with a 2-axis gyrometer and a 1-axis yaw gyrometer to provide the data for the auto-pilot. Initially. the AR.Drone used a QFN-packaged accelerometer, but ACAL suggested migrating to the LGA-packaged BMA150. This reduced both the power consumption and cost," from [http://www.acaltechnology.com/index.php?page=news&id=3634|here.] the datasheet is available [http://www.bosch-sensortec.com/content/language1/downloads/BMA150_DataSheet_Rev.1.5_30May2008.pdf|here]. Just in case you need the navigation board, is is available at places [http://ardrone.parrotshopping.com/us/p_ardrone_product.aspx?i=199966|like this.] Hope this helps, good luck.