[0] - https://en.wikipedia.org/wiki/1994_Fairchild_Air_Force_Base_...
[1] - https://theaviationgeekclub.com/the-story-of-bud-holland-the...
The story from your [0] about one of the crew's last flight with his family on the ground waiting for the post-flight rituals where his wife and 2 kids watching is just horrific. What a fucking asshat of a person.
It’s positive G, but 0.5 up to 2G (otherwise, given that lift is “towards the ceiling of the plane”, so not always straight up during the manoeuvre, you’d accelerate downward, and arresting the fall requires >1G).
Maybe "safe" here means that merely the stress of the maneuver itself wouldn't destroy the craft? But surely the loss of lift is likely to put it at significant risk, as in your example.
Video on youtube: https://www.youtube.com/watch?v=iz1Eze3QrDU
Counterintuitively though my understanding is that barrel rolls are generally safe even for large planes since it's a stable 1G maneuver (some jock irresponsible air force pilot used to regularly barrel roll B-52s until he did one too low and killed himself and the crew)...