A key area of focus during the first day of the NTSB investigative hearing on the Jan. 29, 2025 midair collision of American Airlines Flight 5342 with a U.S. Army Black Hawk Sikorsky UH-60L helicopter is the helicopter’s air data system and barometric and radar altimeter discrepancies. The accident resulted in the deaths of all passengers and crew on the CRJ700 airliner and the three crew members on the Black Hawk.
To conclude on August 1, the hearing will not generate any conclusions as to the cause of the accident. During opening remarks this morning, NTSB chair Jennifer Homendy explained, “An investigative hearing allows the NTSB to gather sworn testimony from witnesses on issues identified by the investigative team for a specific event or systemic safety issues. Investigative hearings are fact-finding proceedings. The purpose is to receive testimony and evidence, which may be of aid in determining the cause of an accident. This is not an adversarial hearing.
“The board does not permit cross-examination of witnesses in the legal sense, nor do we permit questions related to fault, outside litigation, or legal liability in general. Such questions are not relevant to the fact-finding purposes of an investigative hearing conducted by the NTSB or our statutory mission. This does not mean difficult questions won’t be asked. They will be, and they should be. This is an investigation. We are here to improve safety. That is our sole focus.”
The nighttime Black Hawk flight was an annual evaluation for the pilot using night-vision goggles along helicopter routes near Washington, D.C., and the weather was visual meteorological conditions. The Black Hawk’s callsign was PAT 25. Flight 5342 was a PSA Airlines CRJ700, callsign Bluestreak 5342, doing business as American Airlines Flight 5342, flying from Wichita to Ronald Reagan Washington National Airport (KDCA). Flying along Route 1 from Cabin John, Maryland, along the Potomac River to Washington, D.C., the helicopter went past Hains Point, where Route 1 transitioned to Route 4, then past DCA and the Wilson Bridge. South of the Memorial Bridge to the Wilson Bridge, the maximum altitude along Route 4 is 200 feet, and where Route 4 crosses near the final approach glide path to DCA’s Runway 33, the difference between the route’s 200-foot maximum altitude and the altitude of the aircraft on final approach is only 75 feet. (Those routes have subsequently been moved elsewhere.)
According to the NTSB preliminary report on the accident, the Black Hawk’s radio altimeter indicated 278 feet at the time of the collision, and the CRJ’s final recorded radio altitude was 313 feet.
During the hearing, the NTSB’s technical panel noted, “Investigators identified discrepancies related to the accident helicopter’s altitude, leading to additional investigative work to determine the validity of the altitude information displayed to U.S. [Army] pilots and the altitude data recorded by the helicopter’s flight data recorder, or FDR. “While the radio altitudes of the crews and the helicopter…were within 10 feet at the approximate time of impact, the helicopter’s corrected pressure altitude was 100 feet lower than the CRJ’s corrected pressure altitude.”
These discrepancies led the NTSB to conduct altimeter tests using Sikorsky UH-60L helicopters from the same battalion as the accident helicopter. During the tests, the right-seat pilots wore cameras that recorded the instrument panel. The NTSB downloaded the FDRs from each helicopter after the tests to compare the data to the cockpit instrument videos.
What the tests found was that before engine start, the barometric altimeters of all three helicopters were within 20 to 45 feet of field elevation. Once in a hover, “The barometric altimeter readings dropped significantly and were lower than the helicopters’ actual on-the-ground elevation or hover altitude. Notably, the barometric altimeters continued to be 80 to 130 feet lower than the helicopters’ determined altitude above sea level [MSL] when flying at speed over the tidal portion of the Potomac River later in the test…In summary, we found discrepancies between the FDR pressure altitude and determined height above sea level for the accident.”
Asked about these discrepancies, an Army representative explained that the altimeter tests were “an anecdotal event. It doesn’t use the standard flight test methods that the military and the FAA would use in order to characterize a pitot-static system. So there’s not an independent truth measurement of barometric pressure.” He also pointed out that one of the three helicopters had an out-of-specification altimeter due to an inoperative vibrator. “So that right altimeter data would be in question for that aircraft.”
Much of the morning portion of the hearing focused on how Army pilots could detect such a discrepancy and whether they could tell when flying by reference to barometric altimeter readings whether they were off by 100 feet. Asked about which reference pilots use when flying at low altitudes, Army Black Hawk pilot and chief warrant officer Kylene Lewis said, “In my experience, when flying at low altitude, I would be referencing the radar altimeter.” Asked when she would transition between the two, she said, “Certainly 200 feet and below, I would be referencing the radar altimeter. However, if I was flying on a published MSL route, I would be referencing barometric altitude.”
She was asked, “Could you pick up on a difference visually, looking out the window, between flying at 200 feet versus 300 feet, is there enough of a difference at those altitudes?”
“That’s a difficult question to answer,” Lewis responded. “I’m not sure if you’d be able to resolve that difference…I don’t know that I could 100% accurately determine the difference in altitude.” Lewis also clarified that she had not flown the routes near Washington, D.C.
Lewis was later asked if she had reviewed material in the NTSB docket, and she responded, “I’ve reviewed all of the material for the air data systems and altimeters.”
“Did you find anything disturbing in what you read?”
“In my opinion, the amount of clearance between the helicopter route and potentially the altitude of an aircraft passing over top of it was concerning.”
The hearing continued with further discussions of the Black Hawk’s pitot-static system design, FAA and military standards for altimeter and pitot-static system design, and the Army’s plans for updating flight manuals to let pilots know about altimeter discrepancies, which is expected by September.
“I hope every Army aviator is not having to watch the NTSB…livestream to figure out that there’s a discrepancy in the altitudes of the planes that are flying around us,” said the questioner (whom AIN was unable to identify, due to problems with the livestream). “Sorry for my frustration.”