Well 'On Fire' is one good example. Another reason would be that you don't want to spend half an hour descending from FL180 at 600 ft/min.
To reduce your energy by flying in a high drag configuration, means you either have to fly close to Vs, or just under Vf with flaps deployed, or between Va and Vne without flaps. All of which needs to be done with caution. I think that just below Vf is the safest way, and may result in the most amount of drag.
edit.. Just thought of another reason for a fast descent, maybe only applicable to larger aircraft... Loss of Cabin Pressurisation, at higher FLs.... Usually these wings have Speed-Brakes, which help a lot to achieve a high RoD.
Last edited by scifi; 21st September 2023 at 13:19.