Federal safety investigators said that the military helicopter that collided with a commercial flight from Wichita last month may have had inaccurate altitude readings in the moments before the crash, and the crew may not have heard key instructions from air traffic controllers.
National Transportation Safety Board Chairwoman Jennifer Homendy told reporters Friday that the Black Hawk's cockpit recorder suggested an incomplete radio transmission may have left the crew unable to hear air traffic control tell them, just before the crash, to move behind the jet.
“That transmission was interrupted -– it was stepped on,” she said, leaving the helicopter’s crew unable to hear the words “pass behind the” because their microphone key was pressed at the same moment.
The collision likely occurred at an altitude of about 325 feet, investigators have said, which would put the Black Hawk above its 200-foot limit for that location.
Cockpit conversations a few minutes before the crash indicated the crew may not have had accurate altitude readings, with the helicopter’s pilot calling out that they were then at 300 feet, but the instructor pilot saying it was 400 feet, Homendy said.
“We are looking at the possibility there may be bad data,” she said.
That generation of Black Hawks typically has two types of altimeters – one relying on barometric pressure and the other on radio frequency signals bounced off the ground. Helicopter pilots typically rely on barometric readings while flying, but the helicopter’s black box captures its radio altitude.
Since the crash, the NTSB has recovered all the flight data recorders and pulled the wreckage of both aircraft from the Potomac.
It will take more than a year to get the final NTSB report on the crash, but officials have been providing regular updates as investigators learn more and they plan to publish a preliminary report in the coming weeks.
The collision occurred as American Airlines Flight 5342 was preparing to land at Reagan National Airport. The U.S. Army Black Hawk was on a training exercise, practicing emergency evacuation routes that would be used to ferry out key government officials in case of an attack or catastrophe.
A few minutes before the twin-engine jet was to land, air traffic controllers asked if it could use a shorter runway. The pilots agreed, and flight-tracking sites show the plane adjusted its approach.
Shortly before the collision, a controller got an alert that the plane and Black Hawk were converging and asked the helicopter if it had the plane in sight. The military pilot said yes and asked for “visual separation” with the jet — allowing it to fly closer than otherwise may have been allowed if the pilots didn’t see the plane. Controllers approved the request.
Roughly 20 seconds later, the aircraft collided.
All 64 people onboard the flight from Wichita were killed, as were the three members of the helicopter crew.
The collision was the deadliest plane crash in the U.S. since 2001, when a jet slammed into a New York City neighborhood just after takeoff, killing all 260 people on board and five more on the ground.
