Ethiopian Airlines pilots initially followed Boeing procedures pre-crash

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But the pilots failed to regain control of the system, and the MCAS was reactivated again-triggering yet another automated correction of the aircraft's stabilizers that would have pushed the nose of the plane down.

Last week, the acting FAA administrator went to Capitol Hill to defend the government's response to the two crashes.

John Goglia, a former member of the National Transportation Safety Board, said MCAS was designed largely to reduce the nose-up effect during takeoff and avoid a risky aerodynamic stall, or loss of lift from air flowing over the wings.

Air Canada, which previously suspended its 2019 financial forecasts, has removed 24 MAX jets from its flight schedule until July 1, following grounding of the Boeing jets after two recent crashes involving the model.

"Given the many serious questions surrounding the Boeing 737 MAX and the FAA's certification process, it has become abundantly clear that an independent body must be able to review every step of the process and help restore public confidence. well before the MAX is allowed to be restored to service", DeFazio said in a statement.

It said the flight crew performed different scenarios that exercised various aspects of the software changes to test failure conditions for its Maneuvering Characteristics Augmentation System, or MCAS. Ethiopian Airlines is also in the midst of an expansion drive, while other 737 MAX customers and victims' families want answers, and potentially compensation.

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Although aircraft experts say MCAS can not turn back on by itself, the report is expected to shed light on whether and why the crew chose to restore electrical power to the system at the risk of setting off more automated nose-down movements. They have lost more than 8.5 per cent since the Ethiopian crash.

The Wall Street Journal report, citing unidentified people briefed on the matter, said the pilots had initially shut off the anti-stall system called MCAS that was pushing the airplane's nose down shortly after it took off from Addis Ababa. Boeing is in the midst of upgrading the software while adding extra training.

A directive issued after the Indonesian crash instructed pilots to use cut-out switches to disengage the system in the event of problems and leave it switched off.

Boeing's new MCAS flight control system for its 737 MAX aircraft appears foolproof, Norwegian Air Chief Executive Bjoern Kjos said on Wednesday after visiting the plane maker in Seattle. Soon after, the pilots restored power to the horizontal stabilizer.

Aerospace analyst Bjorn Fehrm said in a blog post for Leeham News that pilots may have deliberately re-activated the system in order to make it easier to trim or control the aircraft only to be overwhelmed too quickly by counter-moves from MCAS.

Safety experts stress accidents are usually caused by a combination of factors and the probe is at an early stage.

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