Canadian regulators—citing satellite tracking data that suggest the flight profile of the Ethiopian Airlines 737 MAX that crashed March 10 is similar to that of last October’s Lion Air MAX 8 accident—has banned all MAX operations in Canada until further notice.

The move, announced at 11:45 a.m. Canadian eastern daylight time March 13 and done via a safety notice, is based on data received overnight and reviewed “this morning” by Canadian aviation experts, Transport Minister Marc Garneau said during a press briefing. 

The satellite data analyzed included Ethiopian flight ET302’s course, vertical profile, and “fluctuation in that vertical profile,” Garneau said. This was overlaid with a similar data set for Lion Air flight JT610.

“We know what happened with the Lion Air flight,” Garneau said. “We wanted to see if the Ethiopian flight resembled it.”

They saw enough similarities to ban MAX operations.

Garneau cautioned that while the links between the two accidents “are not conclusive, there are similarities that exceed a certain threshold in our minds.”

Canada’s grounding justification is the strongest link yet between the two accidents involving newly delivered MAX 8s. In each case, the aircraft departed on early morning flights in clear weather. Both crews soon reported flight control problems and requested to return to their departure airports. Soon after, both went nose down at high speed and crashed.

The JT610 accident probe is focusing on erroneous sensor data triggering automatic nose-down inputs generated by the MAX’s Maneuvering Characteristics Augmentation System (MCAS), which helps the aircraft’s performance match the 737 Next Generation (NG) in certain manual flight profiles. 

Faulty data, such as a single angle-of-attack (AOA) sensor telling the aircraft that its nose its higher than it is, can cause MCAS to repeatedly push the nose down with automatic stabilizer deflections to compensate. Pilots can counter MCAS in several ways, including a switch that adjusts the automatic trim. But continuous faulty data will cause MCAS will respond with nose-down input, countering the pilots' inputs. This was apparently the case on JT610. 

Like the 737NG, the MAX includes a cutout switch that completely stops the automatic stabilizer movements—a last-resort step included in a pilot checklist designed to prevent unwanted nose-down input. The JT610 crew apparently did not activate the switches.

Little is known about what happened on ET302’s flight deck. The flight data and cockpit voice recorders have been recovered, but the data has not been analyzed. Airlines and regulators, caught in a state of limbo, have opted to ground the MAX and wait for more information.

The US had been the lone notable exception until shortly after Canada grounded the MAX aircraft when US President Donald Trump announced the US also grounded the MAXs—the last country to do so—in a White House briefing at 2:30 p.m. US ET March 13.

Sean Broderick, sean.broderick@aviationweek.com