The crew of the Army helicopter that collided with an American Airlines jet may have had inaccurate altitude readings in the moments before the crash, investigators have said.
The soldiers may also not have heard key instructions from air traffic controllers to move behind the plane, it was revealed.
NTSB chair Jennifer Homendy said the recording from the Black Hawk suggested an incomplete radio transmission may have left them without understanding how it should shift position just before the January 29 crash, in which all 67 aboard the two aircraft were killed.
‘That transmission was interrupted – it was stepped on,’ she said, leaving them unable to hear the words ‘pass behind the’ because the helicopter’s microphone key was pressed at the same moment.
‘At 8:47:42 – or 17 seconds before impact – a radio transmission from the tower was audible on both CVRs directing the Black Hawk to pass behind the CRJ,’ Homendy told reporters.
‘CVR data from the Black Hawk indicated that the portion of the transmission that stated ‘pass behind the’ may not have been received by the Black Hawk crew.’
Homendy said the helicopter was on a ‘check’ flight that night where the pilot was undergoing an annual test and a test on using night vision goggles.
Investigators believe the crew was wearing night vision goggles throughout the flight and that there was nothing to suggest that the crew had removed them.