Heartbreaking! Hopefully lessons are learned, and taken to heart. I found the comments under that video that
@Andy C posted, very informative. A combination of errors, which normally wouldn't result in an accident, but the errors piled up on each other.
Here's what I got from the video:
Night vision goggles, poor peripheral vision in the helicopter, at night with ambient glare. (other vids with Army training heli pilots mention that 4 people in the cockpit for a training flight is best practice- with 2 people checking the sides of the helicopter while the student and trainer work.)
An Air Traffic Controller understaffed, doing 2 jobs at once. Managing the helicopter and the airplane coming in to land.
An allowed margin of 100 feet clearance which is less than the allowable margin for error in a properly functioning altimeter. That horrified a lot of pilots in the comments.
Last minute runway change.
George used to watch Mentour Pilot who often does a post mortem on these accidents, but he takes his time and waits till all the info is in, and when he can devote time to that video so hes' usually 6 months later. He is a working airlines pilot based in Spain or Portugal. He always mentions the swiss cheese model for accidents, which is that the holes all have to line up. Following procedure usually stops up some hole or other, sometimes more, so the accident can be avoided.