A Transport Canada safety official in an email to his counterparts in the United States, Europe and Brazil outlined his misgivings about the revised 737 Max flight control software and suggested that the only solution was outright removal of the system from the jet’s design.
The Tuesday, November 19 email sent by Jim Marko, manager of Aircraft Integration & Safety Assessment for the Canadian aviation regulator’s National Aircraft Certification Branch, said he is “troubled by the continuance of open issues, and new issues constantly appearing” with the latest version of the Maneuvering Characteristics Augmentation System (MCAS) that are at the center of two 737 Max crashes in 2018 and 2019.
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The email exchange is a small slice of an enormous global engineering and regulatory process that has been unfolding since the crash of Lion Air 610 in October 2018 and Ethiopian 302 in March. His suggested removal of MCAS has yet to manifest as a regulatory requirement, but Marko’s comments provide a window into how expert regulators are evaluating the proposed changes to the 737 Max.
The email and the presentation slides detailing Marko’s suggested path for removing MCAS from the 737 Max were reviewed and published by The Air Current.
Subscribe to TAC“Judging from the number and degree of open issues that we have, I am feeling that final decisions on acceptance will not be technically based,” Marko wrote. “This leaves me with a level of uneasiness that I cannot sit idly by and watch it pass by.”
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“MCAS introduced nasty behaviors that have to be suppressed which are not on the [737]NG. Are we all smart enough to think that we have wrapped a net around anything that can go wrong from hereon in?”
Marko’s conclusion is that “the only way I see moving forward at this point…is that MCAS has to go,” he wrote, emphasizing in his presentation that there was an “urgent” need to boost the confidence of regulators and the public.
His email was accompanied by a 737 Max flight control system diagram and illustrates his suggested re-design and accepting that in certain conditions, the aircraft might not fly precisely the same way as its predecessor. “Yes it does bring and (sic) impact with regards to handling and compliance but it looks more like a something we could easily find a way to accept.”
“Ultimately he’s saying ‘can we make this good enough?'” without adding significant uncertainty and complexity to the Max flight control system, said Peter Lemme a former Boeing flight control engineer.
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Marko said his objective was to suggest a solution that doesn’t turn the 737 Max into the earlier generation 737, but rather exceed the safety of the previous design and “how to get some confidence back to us all that we as Authorities can sleep at night when that day comes when the MAX returns to service.”
It is not clear if removing the MCAS from the 737 Max would be feasible, given the certification requirements related to the responsiveness of the pilot controls when the aircraft is in a high angle of attack scenario in either wings-level flight or wind-up turns. The recent Joint Authorities Technical Review suggested that an “unaugmented” 737 Max without MCAS “would have been at risk of not meeting…requirements due to aerodynamics.”
In its current iteration, Marko suggested that one aspect of the MCAS’s design — a limit on its movement of the jet’s horizontal stabilizer that would always be able to be overcome by pilot controls — was “ineffective” and was an outstanding high risk issue as part of the ISSA or Initial System Safety Assessment. In the case of Lion Air 610, the MCAS system had activated to the point that the nose down trim commands had exceeded the crew’s ability to overcome the forces when pulling back the controls. Marko writes that this “is another point that was just discovered.”
Nicholas Robinson, Transport Canada’s director general said in a statement that Marko’s correspondence “reflects working level discussions between highly trained aircraft certification experts of key aviation authorities who have been given wide latitude for assessing all issues and looking at all alternatives for the safe return to service of the aircraft.
“The views are at the working level and have not been subject to systematic review by Transport Canada.” Air Canada, WestJet and Sunwing Airlines operate 41 737 Max aircraft.
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An FAA spokesman echoed that sentiment. “The FAA and its international partners have engaged in robust discussions at various stages in this process as part of the thorough scrutiny of Boeing’s work. This email is an example of those exchanges.”
Both Transport Canada and FAA said that the 737 Max will not return to service until it has completed testing and the regulators are satisfied the aircraft and its revised training address the issues brought to the fore by both crashes.
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Boeing said in a statement, “we continue to work with global regulators to provide them the information they are requesting to certify the MAX for safe return to service.” The company has said it has been planning to have the 737 Max cleared by the FAA by the end of the year. FAA officials have pushed back on establishing any specific timeline for the jet’s return.
It is far from clear how widespread Marko’s view on MCAS within the regulatory community at this point in the re-development of the Max’s flight control system, but the New York Times said Linh Le, an FAA system safety engineer who received the email, shared his assessment. In an apparent attempt to cultivate and discuss the alternative viewpoint, Marko said to the email’s recipients that he didn’t “have any reservations if you pass this to others in your organization.”
Marko’s email was first reported by the New York Times.
Write to Jon Ostrower at jon@theaircurrent.com
