The critical flights on the updated Boeing 737 MAX that must be flown by Federal Aviation Administration (FAA) pilots before the plane can be certified again are now unlikely to happen before late April, according to two people familiar with the details.
The delay of more than a month from recent plans means that Boeing’s publicly announced goal of winning FAA approval to fly the plane again by “midsummer,” previously considered a very conservative schedule, now looks tight and could slip further.
One person with close knowledge of the required steps said that after the certification flight, assuming all goes well, it could take up to a further 60 days for regulators to complete the remaining steps in the process, which would push out the ungrounding of the aircraft to late June at the earliest.
A person who is familiar with Boeing’s internal efforts, however, expressed hope that the jetmaker can still meet its target schedule: “I think we’re still within the midyear ungrounding estimate. So middle/late summer,” said the second person.
He added that the midsummer target had “a lot of margin built in to deal with emergent issues” like those that have recently arisen.
Still, it was just over two weeks ago that FAA Administrator Steve Dickson told reporters in London that a MAX certification flight could occur “in the next few weeks.” Since then, that schedule has clearly slipped considerably.
Software and wiring fixes pending
Before a certification flight can happen, Boeing must have at least one MAX aircraft ready with all the final fixes and software updates installed. Among the issues to be resolved first are a faulty cockpit indicator light and a decision on whether Boeing must rewire some of the flight control wiring bundles to comply with safety regulations.
During flight tests of the upgraded MAX flight control system this year, an indicator light erroneously came on in the cockpit indicating that the horizontal tail of the jet — the stabilizer that controls the aircraft’s nose-up or nose-down pitch — was “out of trim,” meaning out of position to maintain the pitch the pilot has commanded.
Boeing initially dismissed this as merely a nuisance light that would require a simple software patch and wouldn’t cause a delay.
However, engineers have now established that the problem is trickier to fix than first thought. It stems from a small disagreement between the angles of the two parts of the stabilizer on either side of the tail. Unlike in the original MAX system design, the upgraded MAX now uses both of the plane’s two flight computers to compare data from the two sides of the airplane. The computers note the discrepancy between the angles and the software logic triggers the light.
Collins Aerospace, a unit of United Technologies headquartered in West Palm Beach, Florida, makes the flight control software to Boeing’s specifications. Boeing has tasked Collins with fixing the software, but it’s turning out to be more work than is suggested by the term “patch.”
“We feel good about the software fix to correct it,” said the person familiar with Boeing’s internal efforts. “It will just take some time.”
The other unresolved issue is that the flight control wiring in the MAX does not meet the latest safety regulation that was introduced to prevent electrical shorts. Boeing missed this during original certification. It has proposed to the FAA that it be allowed to leave the wiring as is, based on the safe history of the earlier 737 NG model, which has the same wiring.
But the person familiar with the required steps to certification said “Boeing has a daunting task in making a case that they don’t have to rewire the airplanes.”
The second person, the one familiar with Boeing’s internal efforts, said that a certification flight “is likely in April or May” and that rather than any specific issue, the delay is due to “the overall work on the system safety analysis” (SSA).
The SSA requires detailed analysis of all the possible system failures and estimating a probability for each. The painstaking work of combing through the potential faults and their probabilities is taking a lot of time, he said.
“I don’t ascribe it to stab trim-out light or wire bundles specifically,” the second person said. “This is the most scrutinized plane system, probably ever. Issues that in the past or on any other plane … would be done in service are being asked to be resolved now,” before being allowed to fly again.
After successful FAA certification flights are completed, the MAX must then pass a series of further milestones before it can fly again, a process estimated to take 45 to 60 days.
After the certification flights, the Joint Operations Evaluation Board (JOEB), which comprises the FAA’s Flight Standardization Board (FSB) and officials from foreign regulators in Canada, Europe, and Brazil, will meet to evaluate minimum pilot training needs.
The FSB will issue a report that will be made available for public review during a comment period expected to be about 15 days.
Additionally, the FAA will review Boeing’s final design documentation, which also will be reviewed by the multi-agency Technical Advisory Board (TAB).
After all these FAA technical reviews are complete, Administrator Dickson has said he won’t give the final clearance for the MAX to fly until he has flown it himself and is “satisfied that I would put my own family on it without a second thought.”
For now, Boeing’s target for that remains midsummer. Airlines will need another month at least after that to train their pilots and get their first MAX jets out of storage and readied to fly.
American and Southwest this month removed the MAX from their flight schedules until mid-August. United Airlines has pushed out the MAX until early September.