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Touchscreen controls in the cockpit of an Alaska Airlines Boeing 737-9 aircraft during an event showcasing the latest updates to the ecoDemonstrator program at Boeing Field in Seattle, Washington, U.S., Monday, Sept. 27, 2021. Boeing Co. is exploring how “We want to integrate sustainability improvements into aircraft design, production, maintenance and recycling to prepare for the next commercial aircraft,” said Mike Sinnett, vice president of product development for Boeing Commercial Airplanes. Photographer: David Ryder/Bloomberg via Getty Images
Investigators will never know exactly what Alaska Airlines pilots said last week in the chaotic, loud first moments after a door plug on a Boeing 737 MAX 9 flew away, leaving a hole in the side of its fuselage shortly after takeoff.
Because the cockpit voice recorder – one of the practically indestructible so-called black boxes on board every airliner – has a crucial weakness: a short memory span.
According to US standards, cockpit voice recorders, or CVRs, are designed to record on a two-hour loop. As each cycle repeats, the previous sound is overwritten with new sound – a factor that has impacted 10 investigations in the past five years, including several investigations into near-misses on U.S. runways in 2023, according to Jennifer Homendy. Chairwoman of the National Transportation Safety Board.
“Cockpit voice recorders are not only convenient … they also help us determine exactly what was going on,” she said in a news conference Sunday evening. “And it’s the key to safety.”
This is an anomaly in the age of inexpensive and extensive digital storage, where every passenger's phone on board a flight could easily have more capacity than the plane's voice recorder.
Now Homendy wants the recording standard to change.
It is calling on the Federal Aviation Administration to require a 25-hour recording window for the cockpit voice recorder on all aircraft – a duration that is already standard in European airline regulations.
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The FAA last year proposed requiring a 25-hour recording time for cockpit voice recorders. But it would only apply to newly manufactured aircraft, Homendy noted, adding that she would like the FAA to change its proposal and require retrofitting of currently flying aircraft.
“You can easily install another cockpit voice recorder and extend the time from two hours to 25 hours,” she said Sunday evening.
CVRs are a critical tool in investigators' efforts to shed light on an incident like the one that occurred Friday over Portland, Oregon.
“If we have the CVR, we can somehow match the timeline with everything that happened in the cockpit,” Homendy told CNN's Pete Muntean, adding that investigators would be “able to isolate the smallest sounds.” to shed light on an incident.
“It’s not just about communication – it’s about everything else. You can hear what is happening to the engines. A lot of times you can hear what's happening when the door is thrown open or that headsets have gone flying,” she said. “It is really important.”
There is a process to freeze the recording and prevent further overwriting. A mechanic or pilot can cut power to the recorder and preserve it as a time capsule that can later be downloaded to a specialized laboratory, such as the NTSB's Washington laboratory or France's Bureau d'Enquêtes et d'Analyses.
Alaska Airlines tried that in this case, Homendy suggested in the press conference. After the plane landed in Portland, airline employees were busy setting up their emergency operations center. Finally, they sent a mechanic to inspect the voice recorder.
Jennifer Homendy, chairwoman of the National Transportation Safety Board, speaks to the media about the investigation into Alaska Airlines Flight 1282 in Portland, Oregon, on Saturday, January 6, 2024.
“There was a lot going on, on the flight deck and on the plane. “It’s a very chaotic event,” she said. “The circuit breaker for the CVR was not pulled. The maintenance team went to get it, but after about two hours it was on time.”
“Unfortunately, this is a loss for us, a loss for the FAA and a loss for safety,” Homendy said. “This information is critical not only to our investigation, but also to improving aviation safety.”
Reached for comment on the overwritten CVR and other aspects of the incident, Alaska Airlines told CNN it could not comment and would need approval from the NTSB.
“We have asked the NTSB for permission to answer these questions – they are not allowing us to comment at this time,” the airline said. “We will provide information as soon as the NTSB gives us permission to do so.”
In some cases, two hours is enough: Shortly after the incident, a plane lands and the plug is pulled to save the recording. But in other cases the planes continue to fly. In the case of a dramatic runway collapse last year at New York's John. The pilots took off from F. Kennedy International Airport on the several-hour journey to London after almost colliding with another loaded passenger plane.
While CVRs used to record only the last 30 minutes of a plane's audio, the two-hour recording capacity is still “a nuisance,” CNN Aviation analyst Miles O'Brien said.
“It's kind of scandalous to me these days that we're only recording the last two hours,” he said Monday. “With digital data and hard drives and no more tape loops, we can record for more than 24 hours,” he said.
O'Brien also wants to go beyond Homendy's recommendation: In addition to the audio recordings, he also wants to see video recordings in the cockpit, which he believes will be rejected by the pilots because they see it as an invasion of privacy.
“If what you do can have consequences that lead to the death of others, I think you may have to give up a little bit of your so-called privacy,” he said. “It’s high time we improve the amount of data we get from these cockpit voice recorders, including video.”
CNN's Dakin Andone contributed to this report.