737 Max anti-ice system fix is slow going

Boeing’s own internal assessments put the development, testing and validation of the anti-ice fix at nine to 18 months.

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Release Date
February 29, 2024
737 Max anti-ice system fix is slow going

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Dennis Tajer, an American Airlines captain and spokesperson for the Allied Pilots Association that represents the company’s pilots, shared a photo with The Air Current from a recent flight aboard one of the airline’s 737 Max 8s. Tajer, as pilot in command, had stuck a yellow post-it note above the cockpit navigation display with a reminder to turn off the jet’s anti-ice system after five minutes.

Tajer and other Max crews around the world have been operating with this reminder as part of their normal procedures since August when the Federal Aviation Administration first issued an airworthiness directive that cautioned a risk of severe damage to the Max’s engine inlet structure if the anti-ice was left active “more than five minutes” in a certain set of conditions. 

Related: Boeing’s 737 inlet issue drags on Max 7 certification

Pilots using personalized reminders for all sorts of tasks in the cockpit is extremely common, but the post-it note cue underscores the lack of detailed alerting in the master caution system aboard all generations of the 737, relying on pilot memory to switch off the potentially hazardous anti-ice system. “Easy to get distracted with other duties and miss turning off,” said Tajer, who has been sharply critical of Boeing. “That’s why I use a decades-old technique.”

The FAA was satisfied that deactivation after five minutes was safe, pending a formal upgrade to the Max fleet promised by the end of May 2026. Boeing had planned to ask the FAA to extend the same guidance to the 737 Max 7 to allow it to be certified at the end of last year. 

Even after the accident aboard Alaska Airlines 1282, Boeing planned to press ahead with its request of the FAA. It was only after a meeting between Boeing CEO David Calhoun and U.S. Senator Tammy Duckworth on Jan. 24 that Calhoun was persuaded to abandon the request, he recounted on the company’s earnings call on Jan. 31. Boeing formally withdrew its request on Jan. 29. The FAA’s position on protecting the existing fleet hasn’t changed.

Related: Report: Decades of corporate decision making eroded Boeing safety culture

Even before that meeting, Boeing customers and suppliers viewed Boeing’s Time Limited Exemption (TLE) request of the FAA, which would allow the agency to certify the Max 7 (and the Max 10 by extension) without modification, as politically untenable after Alaska 1282. A Congressionally mandated report on Boeing’s Organization Designation Authorization (ODA) released Monday that presented the company’s safety culture as “disconnected” between its management and workforce has only reinforced that position. On Wednesday, FAA Administrator Mike Whitaker said Boeing had 90 days to develop a comprehensive action plan to improve safety and quality in the company. Calhoun was at the FAA in meetings with Whitaker and others for seven hours the prior day, Reuters reported.

“Boeing must commit to real and profound improvements. We will hold them accountable every step of the way,” said Whitaker.

Related: The fallout for Boeing will extend far beyond the 737 Max 9 grounding

With the requested TLE formally withdrawn, both Max 7 and 10 derivatives face an uncertain timeline for approval as Boeing moves to “incorporate an engineering solution that will be completed during the certification process.” 

Meanwhile, at least one major U.S. airline is monitoring compliance with the requirement to turn off the anti-ice system on its Max fleet in dry air within five minutes. So far, it’s been mixed, as pilots can be occupied with other tasks in a high-workload cockpit, said one senior airline safety official who spoke with The Air Current under the condition of anonymity.

According to two people familiar with the details, the corner case for the risk of damage to the nacelle exists at a combination of concurrent factors, including an altitude between 20,000 and 30,000 feet in level flight, comparatively warm and dry air around 50 degrees Fahrenheit (10 degrees Celsius) and a specific set of engine conditions. Such temperatures at those altitudes are rare.

Related: Boeing exits 2022 with congressional exemption for Max

Today, Boeing has yet to nail down a conclusive fix for the anti-ice system. Several options remain under consideration and its final decision may end up a combination of design changes. The company has activated a multidisciplinary team to focus exclusively on the problem. This so-called “Tiger Team” is getting increased resources to design the modification for the Max 7 and 10. Neither aircraft can be certified by the FAA without this modification.

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“And in terms of the timeline, I would go back to what we said in earnings, which will be inside of a year,” said Boeing CFO Brian West on Feb. 13 during an investor conference — echoing Calhoun’s own expectation of a nine-month process. “Keep in mind that we have to get a robust design. We have to do all sorts of analytical and test protocols, both with the team in Renton, as well as the engine manufacturer. And that just takes time and we’ll take the time. It’s intense and it will be robust and we have to just allow them to do the work.”

But inside Boeing, the process of defining the fix is moving slowly. The company’s own internal assessments put the development, testing and validation of the fix at nine to 18 months, according to those familiar with the company’s planning, showing that leadership’s assessment is at the optimistic end of its own thinking today. That timeline is separate from any additional requirements or evaluations that may present themselves for the certification of both Max derivatives.

The area of vulnerability within the 737 Max engine inlet is at the lower end of the inner inlet ring where temperatures under certain conditions risk causing damage to the structure.
The area of vulnerability within the 737 Max engine inlet is at the lower end of the inner inlet ring where temperatures under certain conditions risk causing damage to the structure.

Southwest Airlines has removed the Max 7 from its planning for 2024, and according to people familiar with its evaluations, the expectation of the airline for flying the airplane is likely not before late 2025 or 2026. Boeing’s assessment before withdrawing the exemption request was to have the fix ready for retrofit on the Max 8 and 9 by the end of May 2026, which remains the plan tied to its August airworthiness directive. United Airlines has also formally removed the 737 Max 10 (previously slated for late 2024 or early 2025), still expected to follow certification of the Max 7, from its planning for the foreseeable future.

Related: United has few good alternatives to 737 Max 10

One airline briefed on the early anti-ice progress said that one possible element of the solution has been in wind tunnel testing. The company hopes to converge on a complete design for the revised anti-ice system as early as March.

The company is focusing its attention on one particular area of vulnerability on the nacelle at the lower end of the inner inlet ring where temperatures under certain conditions risk causing damage to the structure that surrounds the jet’s engines. Boeing’s task is to either bolster cooling or find a way to reduce the temperature of the engine bleed air passing through the inlet.

Boeing declined comment for this article.

Write to Jon Ostrower at jon@theaircurrent.com

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