A 737 MAX 8 of China Southern Airlines departs for a flight to Bangkok. In a move that some see as more politics than safety, China was one of the first countries to ban flights by the 737 MAX 8. (N509FZ)

As investigations continue into the cause of two crashes of Boeing 737 MAX 8 airliners in the span of just five months, Boeing announced that the company is working with the FAA to release a software update to the computerized flight control system that may have played a role in the disasters.

While no definitive causes have yet been identified, investigators are focusing their scrutiny on erroneous readings from the angle of attack (AOA) sensors on the nose of the airliner, and how those readings may have caused the airliner’s Maneuvering Characteristics Augmentation System, or MCAS, to command the airliner’s flight surfaces to lower the nose against the pilot’s wishes. In the case of Lion Air Flight 610, which crashed into the Java Sea shortly after takeoff killing 189 passengers and crew, the two AOA sensors differed by as much as 20 degrees prior to takeoff. The false readings may have led the flight computer to believe the aircraft was in a stall condition during normal level flight. Ethiopian Airlines Flight 302, which crashed two days ago with 157 fatalities, displayed a similar flight profile and flew erratically shortly after takeoff before pilots lost control.

Though the 737 MAX 8 has drawn most of the attention since the crash of two such aircraft in just five months, the MCAS software that is the focus of the investigation, as well as Boeing’s upcoming software update, is present on the whole line of MAX aircraft, such as this United Airlines 737 MAX 9. (Tim Shaffer)

In a press release on Tuesday, Boeing announced that it has been working with the FAA on a software fix for MCAS, and that the update would be released in the coming weeks.

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.

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A 737 MAX 8 of Southwest Airlines. Southwest Airlines. Along with American Airlines, Southwest is the leading operator of the 737 MAX 8 in the US. (Tomás Del Coro)

Despite assurances from Boeing, the FAA, and other regulatory agencies that the 737 MAX 8 is safe to fly, a growing number of airlines and governments have grounded the airliner until a fix has is in place. Following moves by Ethiopia and China to ground the MAX 8 yesterday, England, Australia, and Singapore followed suit today, brining the total to 15 countries that don’t want MAX 8s in their airspace. Vietnam, home to the privately-owned airliner VietJet, which has yet to enter the MAX 8 into service, has said that the government won’t certify the airliner until it is satisfied that fixes have been made. Operations in the US and other countries are continuing as normal while the investigation in to the crashes continues.

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