>inertial force, not orientation. Is there a formula to extract angular >rate information from an accelerometer reading over time? Sure would Integration. That's what we do in the "heading hold" gyros for helis. Andy ================================================================== Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 Hardware & Software for Industry & R/C Hobbies "Go fast, turn right, and keep the wet side down!" ==================================================================