The altitude has nothing to do with it. Separation close in to the runway like that is not by altitude.
The helio was instructed to pass behind the RJ, and did not.
Military aircraft usually work UHF, civilian aircraft are on VHF. No idea how they do that at DCA, but there’s a possibility the RJ crew could not hear the transmissions of the helio. This does not help situational awareness for the aircrews.
Supposedly, the tower (local control) has a brightscope radar as well as windows on the tower cab.
Military pilots are generally very very good. But to fly through the final approach at a busy airport without making absolutely sure there’s nobody there?
Hard to understand.
