It occurs to me that there is one way in which an aircraft could enter a stable and markedly pitch-up attitude without any change of altitude or ground speed, and therefore without any sensation by the crew of acceleration in either the vertical or horizontal direction.
And that is by encountering a strong tailwind. The only sign would be a drop in indicated air speed and the need to pitch up to maintain altitude, and possibly without much need to change the throttle setting.
This might happen near the top of the “hump” over a lenticular cloud, without any reciprocal phenomena later.
Or rather, the reciprocal action by the pilot would be to just to ease the nose down again as the airspeed picked up due to the decreasing tailwind as the aircraft leaves the “hump” behind (with no change in altitude).
There might be up/down draughts as well - I am just trying to discuss the pitch up.
What do you think?
Cheers,
