The National Transportation Safety Board provided an update on Friday into the investigation of the deadly Army Black Hawk helicopter and American Airlines flight collision.
It has been just over two weeks since the crash that killed 67 people - three on board the military helicopter and 64 on board the airplane.
NTSB Chairman Jennifer Homendy said that the on-scene investigation has ended.
The Black Hawk’s mission was what was called a “check ride” or a practical exam for a pilot to be qualified. It was a combined night vision and annual check ride.
The crew was likely wearing their night vision goggles and if they removed the goggles, Homendy said they would have had a discussion among them about going “unaided.” There was no recording on the voice recorder of such a discussion happening.
They were following the helicopter Route 1 and Route 4 as defined by the Federal Aviation Administration. The maximum ceiling for Route 1 varies from 1300 feet outside of the city to 300 feet near the Key Bridge and 200 feet south of Memorial Bridge.
The Black Hawk was flying south from Maryland. The Black Hawk helicopter crew requested to use Route 1 to get to the airfield on Fort Belvoir. It was approved. It started descending as it took Route 1.
The American Airlines flight initially had permission to land at Ronald Reagan Washington National Airport via runway 1 and was preparing to land. They were eventually asked to switch to runway 33 and agreed to do so.
The Black Hawk was flying a mile from the Key Bridge with the pilot saying they were at 300 feet but the instructor pilot indicated they were at 400 feet. Neither was heard on the voice recorder discussing the discrepancy, Homendy said. There is no indication of why there was a discrepancy.
The Black Hawk instructor pilot told the pilot that they were at about 300 feet when they passed Memorial Bridge and told the pilot to descend.
Radio transmission from the control tower told the Black Hawk crew that there was flight traffic near their path, circling to land at runway 33. A portion of the transmission about the circling may not have been received by the helicopter crew. It was heard on one recording but not that of the helicopter. The recorders are being evaluated as to why that could have happened, Homendy said.
The helicopter crew said they had the air traffic in sight.
The American Airlines flight when it turned to land was at a height of 516 feet moments before the crash. Twenty seconds before the crash, a transmission from the tower was received in both the plane and helicopter asking the Black Hawk crew if the plane was in sight. There was a conflict alert in the background of the air traffic control transmission, Homendy said.
The American Airlines flight received an automated alert for traffic in the area.
Seventeen seconds before impact, the Black Hawk was told to pass behind the American Airlines flight, but the portion of the message that was “pass behind the” may not have been received by the helicopter crew, Homendy said. The transmission was stepped on by a .8 second mic key by the helicopter crew.
The helicopter crew then told air traffic control that they saw the traffic and asked for visual separation, the instructor pilot told the pilot that they believe the air traffic control told them to move left, toward the east bank of the Potomac River.
Seven seconds before the collision, the American Airlines flight was on final landing approach at 344 feet. Two seconds before the crash, the American Airlines was at 313 feet.
The Black Hawk was 278 feet and had been steady for five seconds before the crash, Homendy said. She noted that while the radio altitude of the helicopter was 278 feet at the time just before the crash, which may not have been what the crew had been seeing on the barometric altimeter. She said there is conflicting information in the data from the data recorders.
Sean Payne, branch chief of the NTSB vehicle recorder division, said his team will validate the data of the recorders.
He said the radio altitude, which is determined by bouncing a signal to the ground or in this case the Potomac River, was “good data” meaning it was valid. It is not the primary means of determining the height by the pilots.
Pilots use the barometric altitude. That was not recorded flight data recorder and takes into account some atmospheric conditions and displayed on instrument panels.
The barometric pressure setting is an adjustment used on the barometric altimeter and was not recorded by the flight data recorder.
Pressure altitude is an engineering altitude that can be used by the helicopter’s systems but it was not valid. Normally the NTSB can determine the barometric altitude using the pressure altitude but cannot in this case because the data was bad, Payne said.
The NTSB vehicle recorder division is trying to determine how the faulty data impacted the helicopter’s systems, Payne explained.
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