Both the Lion Air crash and the Ethiopian Airlines crash occurred with the 737 Max-8 airplane, but Boeing’s software update appears to be for all planes in the Max line. There’s concern among aviation experts that the two crashes may be related to automation of flight control systems in the plane, but the investigation into what caused Sunday’s crash is still in its early stages.
"Southwest Airlines is currently operating 34 of the 737 Max-8 planes, while American Airlines currently flies 24 of the Max-8 aircraft. United Airlines doesn’t fly the Max-8, though it does have 14 of the Max-9 in its fleet.
For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority," declared the company.
The Boeing announcement insists that pilots are “always” able to override erroneous automation, something that has been a chief concern for those investigating the Lion Air crash. It’s believed that the plane may have pushed its own nose down too far in an effort not to stall and that the pilot was unable to correct for the false reading.
"A pitch augmentation control law (MCAS) was implemented on the 737 MAX to improve aircraft handling characteristics and decrease pitch-up tendency at elevated angles of attack. It was put through flight testing as part of the certification process prior to the airplane entering service. MCAS does not control the airplane in normal flight; it improves the behavior of the airplane in a non-normal part of the operating envelope.
Boeing’s 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018," said the company.
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