There has been a lot of theorising, hand wringing, head scratching, chin rubbing etc on this subject. I quite like Switchbaits post #29... The system works fine, just fly the aircraft. Too much supposition can lead to misinformation and mistakes. What would be ideal is the system description and operation from the Aircraft Maintenance Manual to prove once and for all as to how the system operates and lay this topic to rest. Any engineers out there able to assist this think tank?