The lift generated by a wing is in simple terms perpendcular to the span of the wing. As the angle of bank increases, the vertical component of the lift vector decreases, so the steeper the bank angle the more total lift the wing has to produce to maintain a vertical lift component adequate to keep the aircraft flying level through the air.Kevfin:Wow! Based on my understanding of Bernoulli's principle, I didn't think those things could fly sideways...
For example in a 60 degree bank you have to add enough back stick pressure to increase the lift generated by the wings by a factor of 2 (load factor) to create enough total lift to have a vertical lift component great enough to maintain level flight. In this condition the plane and pilot will be turning due to the excess horizontal lift and will be experiencing centrifical fource equal to 2 times the force of gravity (2 G).
Given how the angles work, the steeper the bank the greater the decrease in the vertical lift component. So if you bank just 15 degrees more to 75 degrees, you need to pull 4 G to maintain level flight. The curve continues to get steeper until 90 degrees where there is no vertical lift component and where an infinite amount of G would not be adequate to sustain level flight (not that you would have the power or ability to sustain the infinite G required.
Consequently, stable "knife edge" flight relies on the lift generated by the fuselage of the aircraft. Most aircraft fuselages are not designed to generate lift in that direction and they are nototiously inefficient at producing lift with the aircraft on it's side.
The ability to sustain knife edge flight varies greatly among aircraft types, with some comparatively light piston engine aerobatic aircraft that were designed with this ability in mind being able to do it reasonably well. But knife edged flight is not a trait usually associated with heavily "wing" loaded jet aircraft.
Even jets with excellent power to weight ratios do not exceed a power to weight ratio of 1 to 1 by very much (perhaps 1.2 to 1.3 to 1 when light on fuel) so thrust vectoring only works to maintain level flight when it is directed at near vertical angles. This is not the case with the BAe Hawk in this picture. In any case, the Hawk is not overly endowed with thrust given that it has a 5700 pound thrust engine, an empty weight of about 8,000 lbs and a maximum take off weight of nearly 19,000 lbs.
I'd guess the BAe Hawk is just short of 90 degrees through a roll or, at best, in a hesitation roll with a brief stop at nearly 90 degrees. The exhaust plume seems to support that.
