(Bloomberg) — Safety investigators probing January’s midair collision between an American Airlines Group Inc. regional jet and a US Army Black Hawk near Washington found a key instrument on the helicopter was displaying inaccurate altitude data that could have led the pilots to think they were flying lower than they actually were.
The US National Transportation Safety Board on Wednesday kicked off a three-day hearing to pour over findings in its investigation into the crash that killed 67 people.
According to the agency, the Black Hawk’s so-called barometric altimeter, which determines altitude by measuring changes in air pressure, was showing the helicopter at 100 feet (30 meters) below the American Airlines jet at the time of the crash.
It’s unclear, however, if the helicopter crew cross-checked that data against other devices like the radio altimeter, which determines altitude by measuring the time it takes for radio waves to travel to the ground and back to the aircraft.
“There is a possibility that what the crew saw was very different than what the true altitude was,” NTSB Chair Jennifer Homendy told reporters during a break in the hearing.
She also said some were very quick to point to pilot error in this case, and while it’s still something the agency is looking at, “it’s possible there was zero pilot error here.”
She said the NTSB is considering whether it should release any urgent safety recommendations on the altimeter issue before the agency puts out its final report, adding that she hadn’t been satisfied with the Army’s responses so far on how they would address the problem.
Documents released from the NTSB’s investigation show a typically hectic night in the airspace over Washington area, with controllers juggling communications with a steady stream of commercial jets along with military helicopters and an air ambulance.
“He’s got ‘em stacked up tonight,” the instructor on the doomed Black Hawk noted to the pilot he was instructing, according to the helicopter’s cockpit voice recording.
Kylene Lewis, a representative for the US Army, said there’s no official policy on which altimeter pilots must use or whether they have to compare data across devices. She also said Army pilots are supposed to check their barometric altimeters before flights and as long as they’re within a 70-foot margin of error, they’re considered suitable for use.
The NTSB had previously said it was looking at whether the helicopter may have been getting faulty altitude readings, but this is the first time the agency confirmed findings on that front.
As part of their probe, investigators tested three other Black Hawks that were of the same model — Sikorsky UH-60L — and from the same Army battalion as the accident helicopter. They found when they flew the aircraft over the tidal portion of the Potomac River where the crash occurred, their barometric altimeters showed them being 80 to 130 feet lower than their actual altitude above sea level.
The midair collision close to Ronald Reagan Washington National Airport, which was the worst US civil aviation disaster in decades, sparked renewed concerns about aviation safety and led to a crackdown on helicopter flights near the airport. It also helped galvanize support for major upgrades to the nation’s aging air traffic control system.
The public sessions are digging into the equipment on the Black Hawk helicopter, the crowded airspace and air traffic control training and procedures at the hub. There are often multiple factors that lead to a tragedy like January’s midair collision.
The Army Black Hawk, with a three-person crew on a training mission, was flying above a 200-foot limit imposed on helicopters in the area. Investigators have also found the pilots appear to have missed a key instruction from air traffic controllers to “pass behind” the American CRJ-700 regional jet. In addition, the Army pilots were also likely wearing night-vision goggles, which can impair peripheral vision.
The helicopter also wasn’t broadcasting its position using a technology known as ADS-B Out, which would have helped give air traffic controllers and other aircraft more precise information on its location.
The NTSB has previously said it’s unclear whether the crew of the Black Hawk purposely turned off ADS-B Out or if there was some other issue with their equipment.
The helicopter hadn’t relayed location data in the two years prior to the accident, Homendy has said. Eight other Black Hawk helicopters from the same Army fleet had stopped transmitting data at some point between May and November 2023, even when ADS-B Out was turned on, she told lawmakers in March.
The accident also drew attention to the notoriously congested airspace near Reagan National airport — a favorite of tourists, lawmakers and power brokers thanks to its close proximity to the US capital.
It boasts the country’s most active runway, feeding commercial planes into airspace jam-packed with other civilian and military aircraft, including helicopters.
Just a few months after the midair collision, two flights into Reagan were forced to abort landings in May due to a nearby US Army Black Hawk helicopter that was traveling to the Pentagon.
The NTSB identified more than 15,000 instances since October 2021 in which commercial planes and helicopters came within an unsafe distance. That includes 85 times when aircraft were separated by less than 1,500 feet laterally and less than 200 feet vertically.
The captain of the plane that landed immediately before the crash later told accident investigators that he’d declined a request by controllers to land on the airport’s lesser-used diagonal runway after discussing it with his first officer, who was nervous about handling the landing. But, he heard the doomed American jet behind him accept the instruction.
“Controller seemed exceptionally busy, that did catch my attention, that he seemed a little task saturated, but it’s not unusual for them to be real busy,” said the pilot, whose name was redacted. “It caught my attention because he seemed a little bit … overloaded, let’s put it that way.”
–With assistance from Julie Johnsson and Mary Schlangenstein.
(Updates with additional details from hearing from fourth paragraph.)
More stories like this are available on bloomberg.com
Source link
[ad_3]
[ad_4]