vapilot2004 says
You don't set a rate of descent. You basically close thrust ( open descent on the Bus ) and then the Elevators control the speed that you have selected. Therefore the rate of descent will vary.
Agreed but there is no normal operational reason for an oscillation in the resulting V path.
no normal operational reason for an oscillation in the resulting V path
In nil wind that would true, but the real world is not like that. As you descend (or climb) the head/tail wind component will change. That will change your IAS and if you have select a 'pitch for speed' mode, the pitch attitude (and thus the V/S) will change to maintain the selected speed.