I encountered a unique situation climbing out of Sondrestrom Fiord, Greenland. At approx FL130, on a clear moonlight night, when approaching a large lenticular cloud, but 3-4000 ft above it, the aircraft increased climb very rapidly, +5000 ft/min; the aircraft pitched up peaking at 30 deg, even with full forward stick. Control was regained after approx 1 min at FL180.
I don’t know which side of the cloud I was on, up-draught or down-draught, but the aircraft transited the full extent of the cloud and did not encounter any reciprocal effects.
I have seen similar, but not the same effect, very close to large thunderstorms (close-up for flight tests; too close for passengers). The overall levels of turbulence were high and even though the aircraft would climb/descend like a lift (elevator) in the very severe up/down-draughts there was no sustained change in pitch. However, any pitching tendency could have been masked by the requirement to maintain constant pitch attitude, and thus with a tight control loop, any stick force could have been masked by a high adrenalin level.
NsF, I don’t follow your logic about pitch up/down. If an aircraft encounters an updraft the relative wind increases the airspeed vector and AoA; this gives more lift and a change in pitch trim, generally nose up (aircraft flying faster requires forward stick). What’s the alternative point of view?