737 Max 8
The first 737 Max 8 takes off on its maiden flight in January 2016. (Photo: Boeing)

U.S. Grounds Remaining Boeing Max 8s and 9s

The U.S. Federal Aviation Administration grounded all remaining Boeing Max 8s and Max 9s on March 13. The decision came just hours after Canada moved to ban the models from its airspace based on new satellite data that suggests similarities between this week's crash of Ethiopian Flight 302 and the October 29 crash of Lion Air Flight 610. The FAA said it based its decision on evidence collected at the site of the Ethiopian crash and “newly refined” satellite data. American Airlines, Southwest Airlines, and United Airlines had stood as the last operators of the type following moves by the rest of the world’s aviation safety authorities to suspend their use into and over their territories. U.S. President Donald Trump announced the "emergency" order at about 2:30 p.m. Washington time.

The move by the U.S. marked an abrupt reversal after the FAA on Tuesday said its latest review showed “no systemic performance issues” and no basis for grounding the aircraft. However, a chorus of calls for grounding the airplanes by U.S. lawmakers on Tuesday and Wednesday along with Trump’s own stated misgivings placed pressure on aviation authorities.

Senator Richard Blumenthal of Connecticut suggested that the government shutdown earlier this year might have interrupted the FAA’s work with Boeing on releasing a planned software upgrade meant to mitigate the suspected problem that led to the October crash of the Lion Air flight into the Java Sea, killing 189 people. The FAA, however, had initially stood by its decision only to issue a Continued Airworthiness Notification to the International Community (CANIC) that reiterates directives arising from the Lion Air crash.

“External reports are drawing similarities between this accident and the Lion Air Flight 610 accident on Oct. 29, 2018,” said the FAA. “However, this investigation has just begun and to date, we have not been provided data to draw any conclusions or take any actions.”

The CANIC noted that the FAA plans to issue an airworthiness directive next month that codifies certain flight-control-design changes underway at Boeing. The changes include activation and angle-of-attack signal “enhancements” and a maximum command limit of the maneuvering characteristics augmentation system (MCAS). Meant to improve pitch response at high angles of attack and prevent pilots from raising the airplane’s nose too high, the MCAS in the 737 Max 8 and Max 9 does not appear in the 737 NG. Engineers made the change to address differing stall characteristics in the Max resulting from its larger and heavier CFM Leap-1B engines. The MCAS can, however, force the airplane into a dive under circumstances such as faulty inputs from its angle-of-attack sensor, potentially leading to a crash, according to a November 7 emergency airworthiness directive issued by the FAA.

Boeing said it recommended to the FAA on March 13 that the fleet be grounded. The company noted that it "continues to have full confidence in the safety of the 737 Max,” but added that after consultation with the U.S. Federal Aviation Administration, the U.S. National Transportation Safety Board, and aviation authorities and customers, it had determined "out of an abundance of caution and in order to reassure the flying public of the aircraft’s safety" that it should recommend a temporary suspension of operations of all 371 aircraft in the 737 Max global fleet.

Show comments (1)

It would appear to be a combination of issues that could be contributing to the problem: Could be that AOA sensors, Could be data going into and coming out of DADC, or an electrictronic interference somewhere.

However, in my humble opinion, the problem was created during the design phase. You don't create an MCAS "patch”for basic design challenges. I have read from a number of sources that the aircraft exhibits some pitch up characteristics due to the larger engines, their installation and orientation. So rather than go back and refine the design, they decided to us MCAS to prevent the nose up problem during climb out. Do I think the aircraft should have been grounded? Not necessarily, but it seems there could be some kind emergency AD put out to do simple things, like, limit autopilot operation until the aircraft has reached a certain altitude, where pitch isn't a problem, or second segment climb. There could have been other temprorary measure invoked too. I don't know a lot about the max. Only what I've been able to read.

I just think this type has been pushed to far, and deviated too much from the original type certificate. Other manufacturers have done similar things. Why isn't FAA stopping this? If Boeing had designed a new type, they wouldn't have been making engineering compromises along the way. That’s not acceptable.

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