Boeing said the 737 Max 8 is a “safe airplane” and it is developing a flight control software upgrade in the wake of the Ethiopian Airlines crash on Sunday (10 March) that killed all 157 passengers and crew on board.
The US aircraft manufacturer released a statement, just as more country aviation regulators ordered their airlines to stop flying the 737 Max 8 – adding to those announced yesterday including Ethiopian and regulators in China and Indonesia.
Singapore’s aviation authority has suspended use of the aircraft and said the affected airlines include SilkAir, which operates six Boeing 737 Max 8 aircraft, as well as China Southern Airlines, Garuda Indonesia, Shandong Airlines and Thai Lion Air.
The Australian aviation regulator has also suspended use of the 737 Max 8. The move affects only Singapore Airlines subsidiary Silk Air and Fiji Airways, as no Australian carriers use the model.
Aerolineas Argentinas, Aeromexico and Gol also said they have temporarily grounded the aircraft. Aerolineas operates five 737 Max 8s, Aeromexico six and Gol seven.
The US Federal Aviation Administration (FAA) told airlines yesterday it believes the model to be “airworthy”, despite the second fatal crash of the 737 Max 8 in less than five months after a Lion Air 737 Max 8 crashed on 29 October killing 189.
Boeing said in a statement that it will deploy a flight control software upgrade for the 737 Max “in the coming weeks” and it has been developing the software enhancement in the aftermath of the Lion Air crash, but did not link it to the Ethiopian 737 Max 8 crash.
The US manufacturer said: “The 737 MAX is a safe airplane that was designed, built and supported by our skilled employees who approach their work with the utmost integrity.
“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.”
Boeing continued: “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.
“Boeing has been working closely with the Federal Aviation Administration (FAA) on development, planning and certification of the software enhancement, and it will be deployed across the 737 MAX fleet in the coming weeks. The update also incorporates feedback received from our customers.
“The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement.
“It is important to note that the FAA is not mandating any further action at this time, and the required actions in AD2018-23.5 continue to be appropriate.
“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.
“Additionally, we would like to express our deepest condolences to those who lost loved ones on Ethiopian Airlines Flight 302. A Boeing technical team is at the crash site to provide technical assistance under the direction of the Ethiopia Accident Investigation Bureau and U.S. National Transportation Safety Board. It is still early in the investigation, as we seek to understand the cause of the accident.”