Army Helicopter Might Have Missed Critical Instruction Before Midair Crash

National Transportation Safety Board officials said on Friday that they were investigating what appeared to be confused communications inside the cockpit of an Army Black Hawk helicopter moments before colliding with an American Airlines jet last month near Ronald Reagan National Airport.

N.T.S.B. investigators are still trying to determine whether and how the miscommunications contributed to the collision that killed all 67 people in both aircraft over the Potomac River on Jan 29. The American Airlines regional jet was arriving at National Airport from Wichita, Kan. The Black Hawk crew was carrying out a training mission so the pilot could perform a required annual evaluation flight.

During a news conference, the investigative board’s chair, Jennifer Homendy, gave two instances of when the air traffic controller had given instructions to the Black Hawk three-person crew on how to weave through the busy National Airport airspace that the crew may not have completely received.

The first instance, Ms. Homendy said, involved the helicopter crew members’ possibly not hearing the air traffic controller inform them that the American Airlines jet was “circling” to switch runways for landing. She said investigators could hear that word when replaying the controllers’ communications but noticed it was missing from the Black Hawk’s cockpit voice recorder.

The airplane, American Airlines Flight 5342, was making its final descent after having been transferred from Runway 1, a regular landing strip for commercial regional jets, to Runway 33, a strip used far less often.

Later, Ms. Homendy said, the air traffic controller told the Black Hawk helicopter to pass behind the plane that was seconds away from landing. But based on cockpit voice recorder data from the helicopter a “portion of the transmission that stated ‘pass behind the’ may not have been received by the Black Hawk crew,” Ms. Homendy said.

That is because the Black Hawk’s microphone key was depressed for 0.8 seconds, which meant that those words were “stepped on” — or not audible to the crew during that time — she said.

Moreover, it appears the instructor pilot, later identified as Chief Warrant Officer Andrew Eaves, interpreted the controller’s instruction as telling the Black Hawk crew to move toward the river’s east bank. He relayed that to the pilot, identified as Capt. Rebecca M. Lobach. That is not, in fact, what the controller said, according to Ms. Homendy.

This instruction from the controller to the Black Hawk was critical because, at that point, the control tower had been alerted that the two aircraft were veering perilously close to each other.

The N.T.S.B. is also investigating possible discrepancies with the Black Hawk’s altitude readings. The altitude is another crucial piece of the puzzle because the helicopter was in a designated path where the maximum height was 200 feet above the river. Yet the midair collision appeared to be at about 300 feet, meaning the helicopter was out of position.

Ms. Homendy said that during the flight, Officer Eaves and Captain Lobach appeared to give conflicting information on their location.

At 8:43, when the Black Hawk was west of the Key Bridge, Captain Lobach indicated the helicopter was at 300 feet while the instructor pilot reported that it was at 400 feet.

“Neither pilot made a comment discussing an altitude discrepancy,” Ms. Homendy said. “At this time, we don’t know why there was a discrepancy between the two. That is something that the investigative team is analyzing.”

At 8:45 p.m., as the Black Hawk passed over Memorial Bridge, Officer Eaves told Captain Lobach that they were at 300 feet and needed to descend to 200 feet, Ms. Homendy said. Captain Lobach affirmed that they would descend to 200 feet.

Investigators do not yet know why the helicopter did not move to that altitude.