The NTSB Preliminary Report is out, and it basically only outlines the aircraft movements, flight paths, collision damage and other pertinent facts related to the crash. There are excellent CVR and FDR records from both the helicopter and the CRJ-700. There is NTSB concern over the accuracy of altitude data from the Multi-Purpose Flight Recorder ("MPFR") in the helicopter, and they are currently unsure how this affected other helicopter altitude measuring systems, until further investigation is carried out. The MPFR is a combined CVR and FDR.
In addition, the audio record from the helicopter indicates portions of radio transmissions were not recorded (or heard) - in one case, because the helicopter microphone was keyed when ATC transmission was taking place, and in another section, the word "circling" in the ATC advisory transmission was not picked up by the helicopter recorder, but it is recorded on the CRJ-700 CVR, and on ATC audio recordings.
At the time of the reports release, the NTSB issued an urgent recommendations report, advising immediate steps to be taken, to ensure a major reduction in the level of civilian aircraft and helicopter near-misses, that had been regularly reported in the region, in recent years.
The recommendations report outlines how the helicopter route ("Route 4") along the Potomac River has lax boundaries, and even slight deviation from that poorly-defined route, poses an unacceptably high risk of an MAC with departing or arriving civilian aircraft, that are using the airport runways - especially as flight path altitudes of arriving or departing civilian aircraft over the River, can also have some altitude variations, according to how closely the aircraft is following the glide path or takeoff path.
The NTSB advise that the FAA urgently needs to close the helicopter route ("Route 4") along the Potomac River whilst civilian aircraft are departing or arriving at the airport runways.
However, they also recommend that an alternative helicopter route must be found, to ensure that important Govt, medical, law enforcement, air defense, or presidential transport, can continue at will, and at short notice.
At present there is a NOTAM (active to 31st March, 2025), that prohibits helicopter traffic along the Potomac in the vicinity of DCA flight paths - but that NOTAM also advises that if urgent medical, law enforcement, air defense or Presidential helicopter movement needs to take place along the Potomac River, civilian aircraft will not be allowed to operate along the airport flight paths, until the helicopter has transited the critical zone.
https://www.ntsb.gov/investigations/Documents/DCA25MA108 Prelim.pdf
https://www.ntsb.gov/investigations/AccidentReports/Reports/AIR2501.pdf