Shawn
What was most surprising to me was how often the subtle change in altitude went unnoticed, even by the most experienced SPIFR, EC-135 qualified pilots. In most cases, the HTAWS was the first indication of a problem. One of the factors that make this so insidious is that it all takes place well above the Vmin, typically 60- 70 KIAS. Also the rates of descent are very low (<200 FPM). Throw in night over water, NVGs or the increased workload while communicating to first responders on the ground and you have a recipe for trouble.