Altimeter Error In Black Hawk Also Possible Factor

The National Transportation Safety Board (NTSB) said in a news briefing that the crew of the U.S. Army Black Hawk helicopter involved in the mid-air collision near Washington, D.C., on January 29, may have missed crucial radio calls from air traffic controllers in the seconds just before the accident. There also appears to be confusion over the exact altitude the helicopter was flying when the collision occurred.

Jennifer Homendy, Chair of the NTSB, said that the on-scene portion of the accident investigation has concluded, and further investigation will be conducted off-site at various labs and other secure locations.

When Homendy was asked if there was any indication the Black Hawk crew could see the impending collision before the impact, she said NTSB investigators have no indication that the crew would have seen it.

She said it’s also believed now that the crew was wearing night vision goggles throughout the flight because they were required for the checkout flight for the pilot. Removing the goggles would have required a discussion among the crew but the cockpit voice recorder (CVR) did not contain any evidence of such a discussion.

The NTSB will conduct a visibility study with NVGs to determine what the crew could have seen or not seen.

Homendy said that data from the Black Hawk’s CVR “indicated that the portion of the transmission stating the [jet] was circling may not have been received by the Black Hawk crew.” That radio call was heard on the jet’s CVR but not the helicopter’s.

In addition, the Black Hawk crew may not have heard the ATC instruction to ”pass behind the jet” because that transmission was stepped on (interrupted) by the Black Hawk keying the mic. On the CVR, the instructor pilot can be heard telling the flying pilot that he thought ATC said to move left toward the east bank of the Potomac.

Regarding the helicopter’s altitude, Homendy said the helicopter’s radio altimeter indicated it was flying at 278 feet at the point of collision and they are confident in that data. However, that might differ from what the pilots were seeing in the cockpit on the primary altimeters, which measure barometric pressure.

Homendy said, “We’re confident with the radio altitude of the Black Hawk at the time of the collision, that was 278 feet, but I want to caution that does not mean that’s what the Black Hawk crew was seeing on the barometric altimeters in the cockpit. We are seeing conflicting information in the data, which is why we aren’t releasing altitude for the Black Hawk’s entire route.”

FMI:  www.ntsb.gov/