SASless,
I thought it was Rad-Alt OR IAS that triggered it, but a lot of water has passed under the bridge since then!
The NTSB's issue of Autopilot training is twofold, I think. a) to highlight differences between the HPZ-7000 and HPZ-7600 (of which I am ignorant, having only seen the 7000!) and b) to ensure adequate training in knowledge of the use of coupled modes: how they function and the indications in the cockpit that show what modes are engaged. I assume the A++ in question had a 'round dial' cockpit so annunciations would be limited to the AP control panel and Flight Director control panel. On EFIS a/c the indications are normally presented on the Flight Mode Annunciator strip at the top of the PFD, and the calling and checking of FMA indications should be part of the SOPs for the a/c.
I cannot help but think that either the radalt was unserviceable (hopefully the final report will tell us), or the bugs were set at zero. If they had been set above zero there would have been sudden bright orange light as they passed the bugged height. It's designed to get your attention!
