Under normal circumstances, trim is used to keep an aircraft flying level, but the MCAS makes automated nose-down movements. That would make the situation harder to manage, possibly accounting for their decision to turn the system back on. "It appears the flight crew reactivated electric trim," former Boeing engineer Peter Lemme said. And failing to fully fix the trim before MCAS is deactivated can make it physically impossible for pilots to control the plane, Fehrm said. At speeds up to 250 knots (288 mph) pilots can stabilize trim with the manual wheel.

Source: Ethiopian News April 04, 2019 20:15 UTC