The Federal Aviation Administration said on Monday that it is proposing requiring four key Boeing 737 MAX design changes to address safety issues seen in two crashes that killed 346 people and led to the plane’s grounding in March 2019.
The agency is issuing a proposed airworthiness directive to require updated flight-control software, revised display-processing software to generate alerts, revising certain flight-crew operating procedures, and changing the routing of some wiring bundles.
The announcement is significant, but there are still other major steps, including finalising pilot-training procedures, that must be completed before the 737 MAX can resume flights. The public has 45 days to comment on the changes, and it is still unclear if flights will resume before the end of 2020.
The FAA said in a separate 96-page report released on Monday that it “has preliminarily determined that Boeing’s proposed changes to the 737 MAX design, flight crew procedures and maintenance procedures effectively mitigate the airplane-related safety issues” in the two fatal crashes. The airworthiness directive seeks to require Boeing changes.
The FAA said the changes minimise “dependence on pilot action and the effect of any potential single failure.”
The crisis about the grounding of the once top-selling 737 MAX has cost the US planemaker more than $19bn, slashed production and hobbled its supply chain, with criminal and congressional investigations still continuing.
The FAA’s extensive review has taken more than 18 months and included the full-time work of more than 40 engineers, inspectors, pilots, and technical support staff. To date, the FAA has conducted more than 60,000 hours of review, certification testing, and document evaluation.
The agency is also proposing that 737 MAX operators conduct an Angle of Attack (AOA) sensor system test and perform an operational readiness flight prior to returning each aeroplane to service. The changes are designed to prevent the erroneous activation of a key system known as MCAS tied to both crashes, to alert pilots if two AOA sensors are receiving conflicting data and to ensure flight crew can recognise and respond to erroneous stabiliser movement.
The wiring change will ensure the MAX complies with the FAA’s wire separation safety standards.