US investigators are still trying to determine precisely the altitude at which the Washington mid-air collision occurred, although early indications put the PSA Airlines CRJ700 at 325ft at the time it was struck by a Sikorsky Black Hawk helicopter.
This figure, drawn from the aircraft’s flight-data recorder, has yet to be fully reconciled with initial information obtained from the Washington National control tower suggesting controller screens showed the Black Hawk at an altitude of 200ft near the time of the collision.
National Transportation Safety Board member Todd Inman says the inquiry has “not finalised” the tower data.
“There’s typically, in the [tower] cab ,on that screen, it may be a 4-5s refresh rate,” he says. “But obviously this is something we’re going to be looking at very closely.”
He adds that inquiry has yet to obtain altitude data from the Black Hawk. While he says investigators are “very comfortable” with the CRJ altitude figure – which has an error margin of plus-or-minus 25ft – the inquiry wants to be more certain about the other two altitude data sources.
Given its crucial nature, Inman says the release of only partial altitude information has been the subject of “internal debate”.
“One part of three pieces we have defined,” he says. “Another part, we feel fairly confident but need to get more information. And a third [part] we don’t even have.”
Investigator-in-charge Brice Banning says the helicopter, operating with the callsign ‘PAT25’, was “within the lateral boundaries” of the specified helicopter route, which hugs the east side of the Potomac river shore, and says the ceiling of this route was 200ft.
“We’ve not had the data out of the [flight-data recorder] for the Black Hawk at this time,” he says.
Banning states: “The radar data, where that helicopter is down at 200ft, has less fidelity. So our team is looking into that, but I think it’s important to note that this is a complex investigation. There’s a lot of pieces here, our team is working very hard to gather this data.”
None of the helicopter’s three crew members, nor the 64 occupants of the CRJ, survived the 29 January collision. The regional jet had been inbound to National’s runway 33 when it was hit by the helicopter over the Potomac.
