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By Andrew Tangel and Andy Pasztor
Boeing Co. and federal regulators said they have identified a new software problem on the 737 MAX, further delaying the process of returning the troubled jet to service.
The new issue involves software that is separate from changes to the aircraft's faulty flight-control system called MCAS, according to people familiar with the matter. The software system in question, though distinct from MCAS, is related to an emergency procedure that can be used by pilots to address MCAS malfunctions, these people said.
The plane maker disclosed in a securities filing on Wednesday the Federal Aviation Administration's request to address the new problem, which it said wouldn't be covered by planned changes to the MCAS system.
Boeing said it agreed with the FAA's decision and request and is working on the required software fix.
The software issue involves an emergency procedure that would be used to counteract MCAS if it malfunctions, erroneously pushing the plane's nose down, according to the people familiar with the matter. The FAA identified the problem last week during simulator tests, these people said, after an agency test pilot determined that the procedure took more time than was acceptable to execute.
It wasn't immediately clear whether the new problem was related to software that was original to the aircraft or postcrash revisions in conjunction with changes to MCAS.
Boeing believes it can resolve the issue with a software tweak, these people said. Otherwise, they added, there is a chance that the company would have to replace a computer chip in all 500 MAX planes that have been delivered or built, a process that would add significant delays.
Certification flight tests, an important step before regulators around the world allow the MAX to fly again, had been expected to begin as soon as last week, according to people familiar with the details.
"Boeing will not offer the 737 MAX for certification by the FAA until we have satisfied all requirements for certification of the MAX and it's safe return to service," the company said in its filing.
An FAA spokesman said the agency is following a thorough process and has no timeline for allowing the 737 MAX to return to service. "The FAA recently found a potential risk that Boeing must mitigate," he said.
A total of 346 people died in two 737 MAX crashes in Indonesia and Ethiopia. Regulators around the globe grounded the aircraft after the Ethiopian crash in March.
United Continental Holdings Inc. on Wednesday became the latest U.S. carrier to strike the MAX from its schedule through Labor Day. United said it is pulling MAX flights out of its schedule until Sept. 3, following similar moves by American Airlines Group Inc. and Southwest Airlines Co. United said it is trying to minimize disruptions by swapping out aircraft and using bigger planes in lieu of the MAX, but it will still have to cancel some 1,900 flights in August, or 60 a day.
Wednesday's developments illustrate how unexpected complications can upset months of painstaking preparations to get the MAX fleet back in the air. Boeing originally submitted an MCAS software fix to the FAA in January, and since then the Chicago plane maker has been on a roller-coaster ride of shifting timetables and deadlines for getting the green light from the FAA.
Boeing previously hasn't submitted filings about last-minute changes and delays to the Securities and Exchange Commission.
It isn't clear how long this latest delay may last. The biggest variable, according to one of the people familiar with matter, is whether Boeing can make the required changes entirely through software revisions. FAA officials still have to be convinced that is feasible, this person said. If a new microprocessor or other electronic component is required, the person added, the delay could stretch into months rather than weeks.
In particular, people familiar with the matter said, the software issue relates to how quickly pilots can use electric switches on the control column, or yoke, to get the aircraft into more level flight.
Stabilizing the aircraft is an early step in the emergency procedure, which later calls for hitting separate switches to cut off power to MCAS and the plane's system for electronically moving its rear-horizontal stabilizer that controls the angle of the plane's nose.
The emergency procedure has come under scrutiny in the wake of the crashes.
After a Lion Air 737 MAX crashed in Indonesia in October, Boeing and the FAA emphasized that pilots should use the procedure to disable MCAS in the event it misfired. Pilots in that accident don't appear to have followed the procedure.
But after an Ethiopian Airlines 737 MAX crashed in March, investigators and executives at the plane's operator said the pilots followed Boeing's emergency procedure.
That claim, however, has been sharply disputed by outside pilots, aviation industry officials and safety experts, who say the Ethiopian Airlines pilots didn't appear to have adequately followed the procedure's steps and apparently turned MCAS back on before its fatal nosedive.
--Alison Sider contributed to this article.
Write to Andrew Tangel at Andrew.Tangel@wsj.com and Andy Pasztor at firstname.lastname@example.org
(END) Dow Jones Newswires
June 26, 2019 21:10 ET (01:10 GMT)
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