A Cautionary Tale of Expecting Too Much
About a decade or so ago, I was involved in the substitution of a digital engine fuel control for the old but very reliable hydro-mechanical control on a single (turboshaft) engine helicopter. In order to simplify it and reduce cost, it was in effect, a single-channel system that failed to a manual fuel control. In other words, when the electronics went off line, the pilot had to twist the throttle to maintain rotor rpm just like in a piston-engine helicopter instead of the fuel control maintaining a constant rotor rpm based on the pilot's control inputs.
Our test pilots accepted it, the FAA evaluated and certificated it, the training academy developed a training curriculum for it, and out the door to operators it went.
Unfortunately, the unit was initially a lot less reliable than we thought it would be and when Joe/Jane average pilot had to take over and twist the throttle, he or she often proved inadequate to the task.
After the first couple of crashes following reversion to manual mode were reported, I arranged to fly one for 30 minutes or so and didn't understand what their problem was. My first helicopter flight, like all older helicopter pilots, was in one powered by a piston engine and manually maintaining rotor rpm in takeoff, cruise, and landing was not a big deal even though I wasn't current and certainly not as good as I used to be (although probably never was).
So for a while we tweaked training, improved the unit's reliability, published advisory articles, etc. Nevertheless, the crashes continued. We were expecting too much from a generation who were raised on turbine-powered helicopters and in at least a few cases, older pilots who hadn't twisted a throttle to maintain rotor rpm in a long time.