@MikeD How would it play out at 500 AGL hover versus a 2000 AGL hover, zero forward speed, and engine quits.
Both cases collective full down, and you’re falling like a rock? Being at 2000 allows enough potential energy to be converted into some form of NR, and you’d pull back the cyclic at the last few seconds from the ground?
How does it work on an Astar from 2000?
500 feet gives you zero margin for any error. Remember, that was tested with test pilots who were expecting it and ready to react to it, knowing what they had. For being surprised by it and considering reaction time, 1000 AGL+ is more realistically survivable……depending on one’s piloting technique and how they manipulate the flight controls as it’s occurring. There are ways to help yourself, and ways to make the situation very much worse, in this situation; and the difference between the two is small movements in flight controls.
From 2000 AGL, you’d have to lower the collective quickly to catch the drooping Nr, and keep the helo level, in order to keep the rotor system loaded and allowing the Nr to now reverse itself and begin building as the induced flow goes straight up through the rotor system. As Nr rapidly builds again, you can then lower the nose a few degrees and get some forward airspeed going, even as you are still dropping at a significant VSI. Doing that momentarily i iads the rotor system, and thus serves to both help control the Nr from building too rapidly and overspeeding, while allowing some forward speed to be had that can be converted into a flare and VSI descent arrestment at about 50 feet, to help cushion a landing. Any headwind there might be, only helps the forward speed issue by adding onto it.
Here’s the problem. The above is an extremely precision, finesse, and correct control input at the correct time, maneuver; with very little margins for error or correction of errors. It can be screwed up very easily. Secondly, high hovering auto is not something normally practiced during recurrent, due to its very high risk for things to go bad. Third, helo pilots probably practice normal autos (straight-in, turning) maybe once a year during recurrent, and likely never this specific one, again due to risk. So even if a pilot has seen it, he’s seen it only once per year, and the chance of both reacting correctly, with finesse, and doing it in an instantly and timely manner, is likely not going to happen.
Me personally, im able to perform one from about 1000 AGL (haven’t attempted one any lower yet), but again, that is fully expecting it, being able to react instantly due to expecting it, and in a lighter weight (for training) aircraft with things like heavy cameras and such removed and no extra onboard equipment. If caught by surprise by this, there’d be some degree of flail-factor in immediately entering the maneuver. The only mitigating difference is, when i’m performing a high hover like this, an engine failure is on my mind, so in terms of preparation or expectation, there is that. But if it actually occurred, it would still be a surprise, and even though initial actions would be correct, i’m sure there would still be some sloppiness initially due to startle factor.
Best to remain well outside of this aerodynamic dead man’s zone, give it a wide berth, unless absolutely essential to have to be there. And then, be there for the minimum time needed, not just hang out there. That said, it will be interesting to see what is found with the engine and power train, as they are so highly reliable and robust in this series of aircraft, and hence why i’m keen to know what maintenance had been undertaken, while also looking for any kind of other mechanical failure points.