Somewhat related: I'm curious if the pendulum fallacy also applies to react= ion thrust powered flying objects like helicopters. My instinct says it does? T= hat has interesting implications with regards to the mass distribution of any f= lying copter-like device and implicitly reflects upon the attitude control servo algorythm needed. -- Peter --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .