Selecting low V/S for CDA
Hi,
Flew with a captain recently who got quite annoyed when I selected around -500 V/S in terminal airspace in order to maintain a continuous descent. The other option would have been to go Open Descent (Airbus) and to level off.
Obviously the best possible way to descend for fuel savings and noise is to have the thrust at idle from TOD until established on final (a true continuous descent), however, this requires planning on the part of ATC, and at the airport we were landing at they do not do this. So almost everyone I know selects V/S in order to try to not level off at any point.
Question: Are we just being stupid by selecting V/S and going down at-500 ft/min. Is that captain right? Does this really save any fuel compared to just going down at idle and flying level for a while? Do they amount to the same thing at the end of the day? Is fuel savings only realised on a proper continuous descent from TOD i.e. at idle.