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Boeing to update 737 MAX anti-stall software with three proposed fixes

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Boeing to update 737 MAX anti-stall software with three proposed fixes

Boeing on Wednesday (Mar 27) announced plans to update the anti-stall system on the 737 MAX aircraft, which has been grounded in response to an Ethiopian Airlines crash that killed all 157 people on board.

The Nairobi-bound plane was the same type as the Indonesian Lion Air jet that crashed in October, killing 189 passengers and crew, with some detecting similarities between the two accidents.


In a call with media that offered an update on 737 MAX software and training, Boeing's vice-president of product and development for its commercial division, Mr Mike Sinnett, cited three proposed updates to the system known as MCAS, or Maneuvering Characteristics Augmentation System.


The first will see the MCAS compare information from both the sensors that establish the "angle of attack" (AOA), a measurement that determines how close a plane is to stalling. The previous set-up only linked the MCAS to one sensor at a time, ignoring the other.


If both sensors disagree by 5.5 degrees or more with the flaps retracted, the MCAS will not activate. This, Boeing said, "will eliminate the chance of erroneous data causing MCAS activation".


Next, Boeing said the MCAS will only be activated once per instance during sensor disagreements or what it described as a “non-normal condition”.


“There are no known or envisioned failure conditions where MCAS will provide multiple inputs,” it added.


Thirdly, the MCAS can never command more stabiliser input than can be counteracted by the flight crew pulling back on the control yoke.
“Pilots continue to always have the ability to override MCAS and manually control the airplane.


“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,” said Boeing.


There will also be changes to the 737 MAX’s primary display in the cockpit with an updated configuration to include an alert if the AOA disagrees. In addition, an optional indicator is available for customers who wish to have an electronic AOA indicator on the primary display. Mr Sinnett said that 20 per cent of Boeing’s 737 MAX customers are keen on including the latter to their aircraft fleet.


Additional training will be implemented in light of the MCAS updates, said Boeing. This includes computer-based training and manual reviews. The course is designed to provide 737 pilots with “an enhanced understanding” of the MCAS function, crew procedures and software changes.


Boeing said that currently, to earn 737 type rating, pilots must complete a course lasting a minimum of 21 days. This includes instructor-led classes and simulator training. 


All 737 MAX pilots must complete the additional training prior to returning to flight, the company stated.




 The airframer said its next steps include engagement and feedback with customers and regulators.


However, certification of the updated software is at the discretion of the respective regulators, though it will be first be certified and “scrutinised” by the US Federal Aviation Administration (FAA).


“The rigour and thoroughness of the design and testing that went into the 737 MAX MCAS update give us confidence in its safety. We look forward to working with all our 737 MAX customers as they implement this upgrade - from the software installation through crew training,” said Mr Sinnett.


 A Boeing 737 MAX 8 airplane sits on the assembly line during a brief media tour in Boeing's 737 assembly facility, Wednesday, Mar 27, 2019, in Renton, Washington. (Photo: AP/Ted S Warren) 


When asked by Channel NewsAsia if Boeing would be compensating airlines for loss of 737 MAX-related revenue or if incentives would be provided for new 737 MAX orders, Mr Sinnett declined to comment.


FlightGlobal's Asia Finance editor Ellis Taylor said the update is but a first step towards restoring confidence in the aircraft type.


"It will be a long-term process," he said.

Mr Taylor also believed that training regimes will be tougher and more extensive for the 737 MAX than before.


“Prior to the accidents, the 737 MAX training for pilots who had flown the earlier 737NG was pretty minimal and mostly paper-based,” he added. “I expect that there will also be greater detail on the specific system changes between the (737) NG and the MAX, as that was something that was not really part of the training regime for most pilots.”


Despite the updates, Taylor said the onus is still on Boeing to convince the aviation industry that the changes will not lead to further accidents.


“It is hard to guarantee that at the moment, given we don’t know how much the MCAS played a part in the Ethiopian crash and what other factors may have been involved there.


"It’s important to point out that this fix was developed in response to the Lion Air crash, but it’s too early to say if it would have prevented the Ethiopian crash if it had been made earlier, because the investigation into that event is still ongoing," he said.







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