Summarize this content to 2000 words in 6 paragraphs Officials confirmed the crew of the Army Black Hawk helicopter that collided midair with an American Airlines passenger plane near Ronald Reagan Washington International Airport may not have known it was flying too high and may not have heard critical messages from air traffic control prior to the fatal crash.The Jan. 29 crash over the Potomac River, which happened during an Army “flight check,” killed 67 people. There were no survivors.National Transportation Safety Board (NTSB) Chair Jennifer Homendy said during a news conference Friday that critical messages from air traffic control, relayed to the Black Hawk just seconds before the crash, may have been missed. HARROWING VIDEO FROM MILITARY BASE SHOWS NEW ANGLE OF MIDAIR CRASH CATASTROPHELess than 20 seconds before the collision, a radio transmission from the tower was audible on both cockpit voice recorders (CVR), directing the Black Hawk to “pass behind” the CRJ passenger plane. “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 transmission was stepped on by a .8-second mic key from the Black Hawk, as the Black Hawk was keying the mic to communicate with air traffic control (ATC), according to the NTSB.FAA, NTSB TO BRIEF SENATORS ON WASHINGTON, DC, MIDAIR COLLISIONThe instructor pilot then told the pilot flying that ATC appeared to be asking for the helicopter to move left toward the east bank of the Potomac River.While the NTSB confirmed the Black Hawk was flying too high at a radio altitude of 278 feet, the agency also noted the barometric altimeters in the cockpit may have been showing the crew a different figure.”We are seeing conflicting information in the data, which is why we aren’t releasing altitude for the Black Hawk’s entire route,” Homendy said. “We are looking at the possibility [that there] may be bad data. Were they seeing something different in the cockpit that differed from the [flight data recorder] (FDR) data, which was radio altimeter?” The two previous issues had the possibility of being remedied by the Black Hawk’s automatic dependent surveillance broadcast (ADS-B), which can prevent traffic conflicts by estimating spacing and separation.But the NTSB said it was “not transmitting” during the flight, prompting a review of equipment, programming and whether there was an equipment malfunction.Another possibility, Homendy said, is that the ADS-B was turned off.The agency will continue to investigate, while also assessing visibility concerns. VICTIMS IDENTIFIED IN DC PLANE CRASH INVOLVING AMERICAN AIRLINES JET AND MILITARY HELICOPTERHomendy said the Army Black Hawk crew was likely wearing night-vision goggles throughout the flight, which could have affected what they were able to see in the dark near a bright airport.”It’s going to be a factor in our visibility study,” she said. “We’re going to have to see what was possible for them to see at the time, leading up to the collision and the accident sequence.”Recorder data shows there was no audible reaction from the Black Hawk crew prior to the crash, indicating they were not aware of the impending collision.
