Questions surrounding the Boeing 737 Max 8 crash

Aviation Report
The Ethiopian Airlines plane that crashed Sunday, killing 157, was the same model that crashed in October during a Lion Air flight in Indonesia. The two deadly accidents raised questions and public alarm about the safety of the aircraft, a Boeing 737 Max 8.
After the deadly crash on Sunday, The New York Times asked readers to send their questions about the type of plane that was involved.
More than 1,000 readers responded to the request. Christine Negroni, an aviation writer, a former air safety investigator and the author of the book “The Crash Detectives.” replied to questions. Some of the questions and replies are presented here with due recognition to the US media.
Which airlines have the Boeing 737 Max 8 in their fleet, and what’s the best resource to see what plane will be flying a particular route?
—Shehroz
Around the world, 47 airlines have the Max 8 in their fleet, including airlines on every inhabited continent. But more than two-thirds of the airlines operating the Max 8 have grounded it.
Is the new technology associated with the Lion Air crash new to only the Max 8 series of aircraft? If it is found that the same technology also had a role in the Ethiopian Airlines crash, what sort of repercussions would Boeing be subject to?
—Marcus Bierbaum, Cleveland
The technology that is under scrutiny is the maneuvering characteristics augmentation system, or MCAS. It is part of the flight control software on both the Max 8 and the Max 9. If information from the Ethiopian Airlines crash suggests the software might have been a factor in the disaster, the consequences for Boeing could be severe. It has already begun a costly and complex redesign of the flight control software. It has been sued by families of the victims and suffered a blow to its reputation.
Boeing’s customers have also suffered consequences, as the majority of airlines that fly the Max 8 have grounded their planes or have been told to by their government’s regulators. Additionally, on Tuesday, the European Union and other countries around the world banned Max models from flying in their airspace.
What training is required for 737 pilots to transition to flying the 737 Max 8? Have the requirements changed?
—Don Griffin, Houston
The training required to transition from one model of 737 to the next depends on the airline. The 737 has a “common cockpit” design, meaning that a pilot certified to fly one model can easily move to another. Airlines that use several variants of the aircraft appreciate that flexibility.
A Southwest Airlines captain told me that at his company pilots who will fly the Max 8 are required to watch a video to familiarize themselves with slight differences in the systems and the engines. A spokesman at American Airlines, Ross Feinstein says pilots must review a training manual before moving to the Max.
Are all pilots that fly the 737 Max 8 explicitly trained on Boeing’s MCAS flight control system? Do they learn how it works and how to turn it off if it malfunctions?
—Alexandra Zaporozec, Chicago
Before the crash of Lion Air Flight 610 in October, Boeing had not notified pilots that the MCAS was operating on the Max or that in certain circumstances it might cause the airplane to pitch down. After the Lion Air crash, Boeing sent a service bulletin to its customers, and the Federal Aviation Administration followed up with an emergency directive ordering Boeing to change the airplane flight manual and provide the flight crew with a way to avoid being surprised or reacting incorrectly to the MCAS.
Have pilots on other flights of this plane experienced failure of the sensors and successfully manually overridden the MCAS?
—Jerry Engelbach, Mexico
The day before the Lion Air crash, the pilots who flew the same airplane reported problems with the angle-of-attack sensor, which tells pilots the angle of the airplane as it passes through the air. Maintenance workers at Lion Air replaced the sensor, and the plane was put back in service to fly as Flight 610. Outside of that event, which was revealed after the crash, there have been no other public reports of pilots experiencing this kind of problem.
That said, pilots of any version of the 737 could encounter situations in which a flight control surface on the tail of the airplane can push the nose down unexpectedly, causing the plane to dive. This is a situation they train for in the simulator.
What they could not train for — because they did not know — was that the MCAS would force the airplane into a cycle of repeated dives. The pilot could stop this cycle only by removing power from a control surface.
Is there any reason to believe foul play may have been involved in this crash?
—Rick Thompson, Sanibel, Fla.
Rick, you ask a good question. On the day of the accident, the State Department issued a travel advisory for both Meskel Square, a traditional meeting place in Addis Ababa, Ethiopia, and the city’s Bole International Airport. Government and embassy personnel were advised not to use the airport that day.
That said, so far there has been no indication from the Ethiopian government or anyone else that a terrorist or a criminal attacked the flight. Still, your question reminds us all to keep an open mind about what might have happened to Flight 302.