In what professional circles is the term "Negative Deflection" used when considering the rigging (or otherwise) position of flying controls?
In Loads & Aero for aircraft design you normally use +ve for down deflections and -ve for up deflections of any control surface (at least in my experience - might be that different companies use different conventions?)
Either way, there will be a hinge-line axis system and either up or down will be defined as positive. Makes the maths a lot easier
