awblain
(Delta-v)(Delta-v) = 2g (Delta-h).
As 1kt is very close to about 0.5m/s, for 400kt, Delta-h ~ 200x200/20 ~ 2000m, as HN39 said.
It's for a dragless/liftless object, so more like a bullet than an airliner.
You've contradicted yourself:
saying anything numerical "without drag" is like focussing on a flea while missing a bear it is sitting on.
