European aviation safety regulators have told their US counterpart they want further testing of repairs to 737 Max's troubled flight control systems before the plane is released to return to service.
According to the Wall Street Journal, the EU Aviation Safety Agency (EASA) told the Federal Aviation Authority (FAA) that it was not satisfied with the demonstrations of reconfigured aircraft safety systems involved in two crashes in Indonesia and in Ethiopia that killed 346 people.
Boeing had originally scheduled the aircraft to go back into service by the end of August, but disagreements over the software's details, centered on how the plane's flight control computers now intend to start working together, put that date to a minimum. in late November.
The goal, according to the Journal, is to add redundancy by having both computers work simultaneously to eliminate potential problems due to computer chip malfunctions.
The problem is separate from changes in the defective aircraft maneuverability enhancement system (MCAS), but is related to an emergency procedure that pilots can use to troubleshoot aircraft system problems.
In recent months, Boeing and regulators have agreed on MCAS software revisions designed to reduce horsepower and reduce the likelihood that the system will take action and force the nose of the plane.
Last week, Boeing CEO Dennis Muilenburg said test pilots had completed more than 700 Max flights.
"We are very confident in this software solution and now we are just going through the final steps to make sure that everyone is confident of airplane safety," he said at a public appearance in New York.
The new problem was identified during testing in June when a test pilot found that the procedure took longer than acceptable to perform.
An aircraft manufacturer spokesman said: "We continue to work with regulators to address their concerns and work on the 737 Max software certification process and training updates and safe return of the aircraft to service."
Boeing's latest troubles come when pilots at Southwest Airlines, one of the largest troubled jet operators, sued the company, claiming that grounding 737 Max jets with the loss of 30.000 scheduled flights cost them more than $ 100 million in salaries. . .
In court documents, the Southwest pilots' association accused Boeing of lying when it said the planes were as safe as their predecessors.
"Our pilots are not expected to suffer a significant and increasing financial loss as a result of Boeing's negligence," Jon Weaks, union president, said in a statement. In total, 387 737 Max flown by 60 airlines are grounded.
Boeing shares have fallen 11% since the launch of 737 Max in March, costing the company $ 27 billion in market capitalization. Prior to the crashes, the aircraft accounted for nearly 70% of Boeing's commercial aircraft overall deliveries and 30% of its total operating profit.