Pilots for two U.S. airlines flying Boeing's 737 MAX weren't trained about a key change to an automatic system that's been linked to the fatal crash of a Lion Air jet last month, according to pilot representatives at both airlines.

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Pilots flying Boeing’s 737 MAX for American Airlines and Southwest Airlines were not informed during training about a key change to an automatic system that’s been linked to the fatal crash of a Lion Air jet last month, according to pilot representatives at both airlines.

Jon Weaks, president of the Southwest Airlines Pilots Association, said Monday the airline and the pilots “were kept in the dark.”

“We do not like the fact that a new system was put on the aircraft and wasn’t disclosed to anyone or put in the manuals,” he said in an interview. What’s more, he noted, Boeing and the Federal Aviation Administration have now warned “that the system may not be performing as it should.”

“Is there anything else on the MAX Boeing has not told the operators?” he added. “If there is, we need to be informed.”

In order to protect against a possible stall on the MAX, Boeing made a change to a flight-control system so that it automatically pushes the nose of the aircraft down when a bladelike sensor that sticks out of the fuselage indicates that the nose is pitched up and putting the plane in danger of a stall.

In the Lion Air crash that killed 189 people in Indonesia, investigators have determined that this sensor, the Angle of Attack (AOA) sensor, was feeding bad data to the jet’s flight computer, activating the system and repeatedly pushing the nose of the plane down when in fact there was no danger of a stall.

Tracking data indicate that the Lion Air jet pitched up and down like a roller coaster during the 12-minute flight before the pilots apparently lost control and nose-dived into the Java Sea.

A former Boeing executive, speaking on condition of anonymity because discussion of accident investigations is supposed to be closely held, said that Boeing engineers didn’t introduce the change to the flight-control system arbitrarily.

He said it was done primarily because the much bigger engines on the MAX changed the aerodynamics of the jet and shifted the conditions under which a stall could happen. That required further stall protection be implemented to certify the jet as safe.

Last Tuesday, Boeing sent out a warning bulletin to all airlines operating the plane worldwide informing pilots how to cut off the system if it malfunctions. Next day, the FAA issued an emergency airworthiness directive mandating that all airlines make pilots aware of the procedure.

Early Saturday morning, Capt. Mike Michaelis, chairman of the safety committee of the Allied Pilots Association (APA) at American Airlines, sent out a message to pilots informing them of details Boeing had shared with the airline about this new 737 MAX system  — called MCAS (Maneuvering Characteristics Augmentation System).

“This is the first description you, as 737 pilots, have seen,” the message from the pilots association at American reads. “It is not in the American Airlines 737 Flight Manual … nor is there a description in the Boeing FCOM (Flight Crew Operations Manual). It will be soon.”

The description of MCAS provided by Boeing states that the system is designed to activate only “during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall” and that it is “commanded by the Flight Control computer using input data from sensors and other airplane systems.”

Michaelis’ message told American pilots to familiarize themselves with the procedure for cutting off that system. “At the present time, we have found no instances of AOA anomalies with our 737 MAX8 aircraft. That is positive news, but it is no assurance that the system will not fail,” he wrote.

Only three U.S. airlines are currently flying the MAX, the third being United Airlines. A representative for United Airlines pilots declined to comment until more information is available.

APA spokesman Dennis Tajer said Monday that the detail on the MCAS system “is new information for us.”

He said his training on moving from the old 737 NG model cockpit to the new 737 MAX consisted of little more than a one-hour session on an iPad. The airline doesn’t have simulators specific to the MAX model.

Apart from that, the only MAX-specific training was practicing cross-wind landings, which are trickier in the MAX because the wingtips have large downward-pointing strakes that might touch the ground in hard cross-winds.

But the cockpit displays and systems seemed identical, he said.

“We assumed they were mostly cosmetic differences,” said Tajer. “Why we weren’t informed of this, I don’t know. Pilots are calling us and asking.”

With the revelation that the MAX has a shift in the flight-control system not present on the earlier 737 models, he said, APA safety experts are in “aggressive exploratory mode” to find out all the ramifications.

“We want to know everything about the airplane that we are accountable to fly safely,” Tajer said.

At the “Pilots of America” online chat forum, one American Airlines pilot posted the APA message and then added a personal reaction:

“We had NO idea that this MCAS even existed. It was not mentioned in our manuals anywhere (until today). Everyone on the 737 had to go through differences training for the MAX and it was never mentioned there either,” the anonymous pilot posted. “I’ve been flying the MAX-8 a couple times per month for almost a year now, and I’m sitting here thinking, what the hell else don’t I know about this thing?”

News that Boeing had not informed the airlines of the change was first reported Monday by Bloomberg News.

The fact that U.S. pilots were not informed about the change means that almost certainly the Lion Air pilots too were unaware.

Boeing, sticking to protocols that require any information relevant to the Lion Air crash to come from the Indonesian safety regulators, declined to provide any detail Monday about the MCAS system and why airline pilots were not made aware of the shift in the system.

Instead Boeing offered a statement: “We are taking every measure to fully understand all aspects of this incident, working closely with the investigating team and all regulatory authorities involved,” Boeing said. “We are confident in the safety of the 737 MAX. Safety remains our top priority.”


Read more about the Boeing 737 Max here »