I guess that C17 that crashed in Alaska in 2010 pushed the maximum bank angle at what looked like about 80-90 degrees i guess for whatever speed it was doing, I imagine the Riverfire C17 flight was a little less envelope pushing than than the 2010 one....
I don’t think you understand the relationship between attitude, flight path, and angle of attack.
An A380 could be rolled to 90º angle of bank (you’d need to be in other than normal law to do so), without a negative outcome. And an apparently similar manoeuvre could be done, which would have exactly the same out come as the Alaskan crash.
So...how? Well, all you need is to initiate a reasonably steep climb (exactly as done by the C17 in Brisbane), and then, when you want to level off, simply roll the aircraft, but without applying any extra back stick, so the G loading will remain low. The aircraft will not be turning (much), and the nose will gently slice down towards the horizon. Roll out so that you’re wings level at, or slightly below zero pitch.
Now, let’s do it badly.
Whilst level, at reasonably low speed, roll on lots of bank, and attempt to remain level. As you bank, your lift vector is directed away from the vertical. If you break the generated lift (call it G) into components in which one is vertically up, and the other into the turn, you will need to pull sufficient total G for the vertical component to remain at 1G if you want the turn to be level. If you produce less than that 1 vertical G, then the nose will start to slice downwards into the turn. Sadly though, for a 90º angle of bank, you’d have to pull an infinite amount of G to make that level turn. G equals 1/cos (angle of bank). So, for a 30º angle of bank, you’ll need 1.15G. Go to 60º and you now need 2G. And at 80º, you’ll need almost 6G. Stalling is actually related to angle of attack (note, this is not the angle between the nose and horizon), but it’s generally described as a speed. As you pull more G, your stall speed will increase, in direct relation to the square root of the G loading. The upshot is, of course, that if you’re already at low speed, if you roll on a lot of bank, and then try to pull hard enough to remain level, you’re at risk of stalling the aircraft.
But, like everything in aviation, there can be more players involved. If you’re already slow, so the angle of attack is high, any move that allows the nose to get appreciably below the horizon is dangerous, as you’ll also need more than 1G to get the nose to come up again.
We talk about stalling and angle of attack as if it relates to the entire aircraft, but actually it doesn’t. Angle of attack, on most aircraft, is normally measured at the fuselage. But, as we manoeuvre, the angle of attack can will vary across the span of the wing. If I’m flying along level, and suddenly apply full roll control, the down going wing will experience an increased angle of attack, and the up going the opposite. But, if you are already on the verge of the stall, then it’s possible that by applying a lot of roll input, that you could stall the down going wing, at which point the roll will increase dramatically, and you’ll have departed from controlled flight.
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