It is still unclear when the update will be rolled out.
The MCAS flight control law was originally designed to enhance the pitch stability of the 737 MAX during to make the handling similar to that of other 737 models. The system initiates during manual flight when the aircraft has an elevated angle of attack (AOA) and flaps up.
Boeing Chief Executive Officer Dennis Muilenburg was on hand to witness the demo flight. (Image courtesy: The Boeing Company via Twitter)
“We at Boeing are sorry for the lives lost in the recent 737 MAX accidents. These tragedies continue to weigh heavily on our hearts and minds, and we extend our sympathies to the loved ones of the passengers and crew on board Lion Air Flight 610 and Ethiopian Airlines Flight 302. All of us feel the immense gravity of these events across our company and recognize the devastation of the families and friends of the loved ones who perished,” said Boeing Chief Executive Officer, Dennis Muilenburg, in a statement published today.
“The full details of what happened in the two accidents will be issued by the government authorities in the final reports, but, with the release of the preliminary report of the Ethiopian Airlines Flight 302 accident investigation, it’s apparent that in both flights the Maneuvering Characteristics Augmentation System, known as MCAS, activated in response to erroneous angle of attack information,” continued Muilenburg.
According to Boeing, the MCAS software update will “provide additional layers of protection if the AOA sensors provide erroneous data. The software was put through hundreds of hours of analysis, laboratory testing, verification in a simulator and two test flights, including an in-flight certification test with Federal Aviation Administration (FAA) representatives on board as observers.”
Muilenburg added, “The history of our industry shows most accidents are caused by a chain of events. This again is the case here, and we know we can break one of those chain links in these two accidents. As pilots have told us, erroneous activation of the MCAS function can add to what is already a high workload environment. It’s our responsibility to eliminate this risk. We own it and we know how to do it.”
Although Boeing did not mention when the update would be rolled out, the company provided an outline of the changes:
- Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
- If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
- MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the airplane.
According to these updates, MCAS will reduce the crew’s workload during non-normal flight situations while preventing erroneous data from causing MCAS activation.
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Boeing has also updated its 737 MAX computer-based training to include the MCAS function, associated existing crew procedures, and related software changes. The company will make the training available to all 737 MAX pilots once it is approved.
“This update, along with the associated training and additional educational materials that pilots want in the wake of these accidents, will eliminate the possibility of unintended MCAS activation and prevent an MCAS-related accident from ever happening again,” said Muilenburg.
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William Kucinski is content editor at SAE International, Aerospace Products Group in Warrendale, Pa. Previously, he worked as a writer at the NASA Safety Center in Cleveland, Ohio and was responsible for writing the agency’s System Failure Case Studies. His interests include literally anything that has to do with space, past and present military aircraft, and propulsion technology.
Contact him regarding any article or collaboration ideas by e-mail at firstname.lastname@example.org.