Alf
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?
What does it do in an updraft? AoA increases. The response to this is designed into the aeroplane- it will pitch down to restore- this is called positive stability- when disturbed, it will try and regain its former state. Negative stability is when you disturb the steady state, and the aeroplane diverges from this- ie in a pitch up state, it wants to pitch further up. This is only allowed in computer controlled aeroplanes as a human cannot fly such a machine.