Mine were A319s with a Honeywell box, cannot recall how close or far from the threshold. Being a CDA freak, I would use -V/S all the time. A pronounced, uncommanded positive climb up to lock the GP is something that rings a very distant bell but was weird enough for the brain to store it. Too vague to describe and discuss with colleagues, too infrequent to nail what it was, just a memory of being upset with the machine. Definitely not the F2 balloon effect, which one'd use deliberately if in need for something similar.
Perhaps we need to redefine the scales?
- Look, what is it doing?
- Look, it's doing it again.
- Do not make it do that again.
- I wished it stopped doing this.
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Merry Christmas everyone.