BOAC;
PJ2 - whatever you think of the "5 deg nose-up" it would not have killed all. The a/c would have flown reasonably happily while the UAS drill was actioned. Any stall warning that might have been thus induced could have been actioned as normal.
Respectfully, I disagree.
First, it is clear that maintaining a pitch attitude of exactly 5deg can be problematic and I think that's what happened here - the PF did not have the experience at high altitude flight to achieve precise control and over-pitched in the same way as the PIOs were introduced in roll - (the reductions in roll show that he learned quite quickly about the sensitivity of roll direct).
Second, the moment one begins the climb one reduces predictability and stability at precisely the moment when both are required to retain some situational awareness and assured energy level of the aircraft. Level flight is most certainly more predictable and any pitch attitude required by rote when the circumstances do not warrant it means something is wrong either with the drill itself or the way it is being interpreted and actioned. In my view, both phenomenon are occurring here in various quarters.
By pitching up to "more or less 5deg", with thrust in CLB and A/THR likely disconnected either by the aircraft or as per the UAS drill and in "THR LK" many unknowns are introduced the most critical one being the energy level (speed) of the aircraft while transitioning from level flight to the climb resulting from the increase in pitch with the possibility of a decreasing speed due to a slightly higher than 5deg pitch.
The airplane was stable before, so why momentarily destabilize it by climbing which is what 5deg NU is certainly going to do? Maintaining level flight prevents the introduction of these unknowns and permits a calm cockpit while reaching for the QRH.
In fact, by the time the QRH page is found and the numbers read out, the UAS event would have been over and normal indications would have returned on this flight. As someone said, this should have been a log-book entry.