FORT WORTH, Texas—A review of
737 MAX jets has expanded to include emergency procedures used by pilots on earlier 737 models, further delaying the MAX’s return to service, according to U.S. government officials.
The Federal Aviation Administration hasn’t questioned the safety of older jets currently in service, these officials said, but the broadened review has become a significant factor in adding months to the time expected to get the grounded fleet of 737 MAX jets back in the air.
As part of the FAA’s safety analysis of a proposed software fix for the MAX fleet, these officials said, the agency also is considering changes in how pilots of the entire 737 family are trained to respond when the flight-control computer or other systems erroneously push the plane’s nose down.
That includes the generation of the jetliner that preceded the MAX, known as the 737 NG—some 6,300 of which are used by more than 150 airlines globally and which form the backbone of short- and medium-range fleets for many carriers.
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The agency’s focus on revisiting the justifications for those procedures, which hasn’t been reported before, has made the process of approving the fix to the 737 MAX more complex and time-consuming than the industry and the FAA initially anticipated, the officials said. At a press briefing this week, acting FAA chief Daniel Elwelldeclined to offer a specific date when he expects the MAX to return to service.
“While we are working with the FAA to review all procedures, the safety of the 737 NG is not in question,” in light of “its 20-plus years of service and 200 million flight hours,” a Boeing spokesman said.
The global MAX fleet of around 400 planes was grounded in March, in the wake of two fatal nose-dives triggered by the misfiring of an automated flight-control system called MCAS. The two crashes killed a total of 346 people.
The pending software fix is intended to make it easier for pilots to override MCAS, which moves a horizontal panel on the tail to point the nose down.
Mr. Elwell has said the agency is pursuing “a thorough, robust and complete” investigation of the dual MAX crashes and “we’re looking at everything” from emergency procedures to training to maintenance to previous agency safety signoffs.
Senior FAA officials spelled out details of safety analyses related to older 737 models in briefings to agency inspectors and international regulators earlier this week, the officials said. The FAA’s expanded safety analysis began months ago, according to the officials.
The agency, according to the officials, is re-evaluating assumptions and safety assessments stretching back to the FAA’s initial approval of 737 NG models in the late 1990s, and in some cases versions that flew many years earlier. Unlike the MAX, the NG models don’t include MCAS.
Some previously developed cockpit procedures are partly based on Boeing’s earlier assumptions that pilots would respond in just a few seconds to erroneous nose-down commands, the officials said, and the FAA is evaluating how realistic that might be.
U.S. regulators are reassessing whether Boeing’s proposed software fix for the MAX—combined with potentially revised emergency procedures and checklists—would give pilots somewhat more time to react, roughly 20 seconds.
In April, FAA officials told airline and pilot union officials at a meeting in Washington that the agency was re-examining what is called the runaway stabilizer trim procedure, a series of steps to counteract erroneous nose-down commands, according to Dennis Tajer, a spokesman for the union that represents pilots at
Parts of the procedure may date to the FAA’s original safety certification of the 737 in the 1960s, he said. The review of the trim procedure was earlier reported by CNN.
The FAA is reassessing the extent of force required to manually counteract nose-down commands in extreme circumstances, by turning a wheel—known as the trim wheel—located between the pilots. The necessary force increases with the speed of the aircraft.
The FAA hasn’t decided whether to mandate new or revised training procedures for earlier 737 models as a result of the expanded studies, the government officials said. Airlines could also voluntarily adopt such changes. Regardless of whether the FAA mandates new or adjusted pilot training, it is likely to require changes to language in pilot manuals explaining emergency procedures.
Mr. Tajer said the existing checklist for the trim wheel procedure, which is what pilots reference and train to, might not include all the information aviators need. For example, some Boeing manuals say two pilots may be needed to manually turn the wheel. But other material provided to airlines for their manuals say merely that the wheel could be difficult to turn.
Over the years, FAA rules for approving new planes or derivatives of existing models typically barred emergency procedures requiring two pilots. “There’s signs of a potential weakness of that checklist,” Mr. Tajer said.
Any issues raised by the review need to be resolved before the FAA’s final green light for MAX aircraft to resume carrying passengers, the officials said.
The FAA is conducting its hazard analyses in conjunction with regulators from Canada, Brazil and the EU, according to one of the officials.
On Thursday, after a summit here with international regulators from more than 30 countries discussing the MAX’s return to service, Mr. Elwell said “we got more questions than we got recommendations.”
The summit, originally described by industry and U.S. government officials as a way to garner an international stamp of approval for the proposed fix, ended without any formal consensus or action by the participants. But Mr. Elwell said “we left with the enthusiastic agreement to continue dialogue.”
The FAA also has pressured Boeing to “go back and do a complete new” safety assessment, an update that has added extra time to process, the official said. Boeing is answering some 200 specific questions on that assessment posed by the FAA in the last month, according to another government official.
—Alison Sider contributed to this article.
Write to Andy Pasztor at [email protected]