Boeing CEO disputes MCAS details “intentionally withheld” from airlines

"That's simply untrue," wrote Muilenburg to employees.

In an internal message to Boeing employees Monday, company chief executive Dennis Muilenburg staunchly defended how it handled development and deployment of the 737 Max’s Maneuvering Characteristics Augmentation System.

Muilenburg, in a company message reviewed by The Air Current, disputed media reports claiming the company “intentionally withheld” information from airlines on the stall recovery system now at the center of the investigation into the crash of Lion Air 610 that killed all 189 aboard.

“That’s simply untrue,” wrote Muilenburg to employees. “The relevant function [of MCAS] is described in the Flight Crew Operations Manual, and we routinely engage with customers about how to operate our airplanes safely.”

Related: What is the Boeing 737 Max Maneuvering Characteristics Augmentation System?

Muilenburg’s assertion amounted to Boeing’s most aggressive defense since the October 29 crash and directly contradicts its largest 737 Max customer, Southwest Airlines.

Southwest’s pilots were told by its management last week: “Since it operates in situations where the aircraft is under relatively high g load and near stall, a pilot should never see the operation of MCAS. As such, Boeing did not include an MCAS description in its FCOM.” The Southwest explainer continues: “In this case, MCAS will trim nose as designed to assist the pilot during recover, likely going unnoticed by the pilot.”

A Boeing spokesman declined to comment.

United Airlines’ pilots union leadership defended Boeing and its level of disclosure surrounding the systems differences between the Next Generation and Max models of the single-aisle workhorse. The question surrounding the crash, said Capt. Todd Insler, chairman of the carrier’s Air Line Pilots Association unit, should center on the actions of the Lion Air pilot’s handling of any abnormal operations of the aircraft.

Related: Boeing issues 737 Max fleet bulletin on AoA warning after Lion Air crash 

Muilenburg, who said the loss of the Lion Air flight “is weighing heavily on our collective hearts and minds” defended the company’s workforce and its most popular product. “I have supreme confidence in all of you and our products, including the 737 Max, but when it comes to safety, our standards of excellence can never be too high.”

The company’s top executive wrote that “many question are unanswered” around the ongoing Indonesian investigation, but he argued that “continued media speculation has introduced false assumptions” and “it’s important you know the facts to the extent we can share them at this stage of the investigation.”

Air safety investigators believe erroneous angle of attack data may have activated MCAS, trimming the 737 Max 8’s nose down to command a dive from which its pilots could not recover.

The company plans to brief airlines worldwide on Tuesday regarding the stall recovery system, according to Bloomberg News.

“Regardless of the outcome, we’re going to learn from this accident and continue to improve our safety record,” wrote Muilenburg. “However, we will not share or debate details in the media. It’s not appropriate and would violate the integrity of the investigation.”

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