The Federal Aviation Administration has found a new problem in Boeing's troubled 737 Max that the company must address before the regulatory agency will allow the airplanes to fly passengers again. The discovery further delays the airliner's return to service.
Southwest, American and United Airlines, the three U.S. carriers that fly Max jets, have already pulled the aircraft from their schedules through Labor Day weekend and this latest development could set back the plane's return to commercial flight well into the fall.
Boeing's popular narrow-body aircraft has been grounded since March after an Ethiopian Airlines 737 Max crashed shortly after taking off from the airport in Ethiopia's capital, Addis Ababa, killing all 157 people on board. It was the second crash of a Max plane in five months; as a Lion Air jet crashed in Indonesia last October, killing 189 people.
Investigators link both crashes, in part, to an automated flight control system that acted on erroneous information from malfunctioning sensors and put the planes into nose dives the pilots could not pull the planes out of.
Boeing has developed a software fix for that flight control system, called MCAS, but sources familiar with the situation tell NPR that in simulator testing last week, that FAA test pilots discovered a separate issue that affected their ability to quickly and easily follow recovery procedures for runaway stabilizer trim and stabilize the aircraft.
A statement from the regulatory agency says as part of a process designed to discover and highlight potential risks, "the FAA found a potential risk that Boeing must mitigate."
Boeing says in a statement that the company is working on the required software fix to address the FAA's request. A spokesman told NPR the company is committed to working closely with the FAA to safely return the 737 Max to service.
Just a few weeks ago, officials with the FAA and Boeing had suggested the 737 Max could be certified to fly airline passengers again by the end of this month. Now that timeline is being pushed back at least a few weeks, if not considerably longer.
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There's more trouble for the aviation giant Boeing. The FAA cites a new problem in the 737 Max in addition to the problem linked to two deadly Max plane crashes. Regulators are ordering Boeing to address this new glitch, which could possibly push back the return of the plane by months. NPR's David Schaper has more.
DAVID SCHAPER, BYLINE: Here's how the new problem was discovered. FAA test pilots were in a Boeing simulator last week running through various scenarios to test out Boeing's fix to the MCAS flight control system when they discovered another problem - at least one test pilot was unable to quickly and easily follow Boeing's recommended recovery procedures for holding the plane out of a nosedive, a failure that the pilot called potentially catastrophic.
Aviation industry sources who asked not to be identified say this new glitch is unrelated to the original MCAS system issue that is linked to Max plane crashes in Indonesia and Ethiopia, but instead it appears to be a problem with a microprocessor.
CHRISTINE NEGRONI: It seems as if the processor in the flight control system isn't fast enough to keep up with the pilot inputs or with the - whatever the software patch is.
SCHAPER: That's aviation safety journalist Christine Negroni, who wrote the book "The Crash Detectives." She says the problem could lie in Boeing's initial design of the plane, and she says fixing it is like trying to remove the eggs after they've already been beaten into the cake batter.
NEGRONI: It's very, very difficult to go into interlocking systems and extricate, patch and fix without having some sort of subsequent down-the-line effect, and this is exactly what I believe we are seeing.
PETER DEFAZIO: This is of tremendous concern.
SCHAPER: That's Oregon Democrat Peter DeFazio, who chairs the House Transportation Committee, which has been investigating the 737 Max crashes and how the Boeing plane was certified by the FAA.
DEFAZIO: There's real questions here. We've demanded reams of documents, which were received from Boeing, you know, about how the original problem happened. And this new problem, we don't even exactly know yet.
SCHAPER: DeFazio says this new 737 Max problem, along with reports of design flaws and safety problems at Boeing manufacturing facilities, raises questions about the entire safety culture at Boeing. Christine Negroni agrees and says these concerns are not new.
NEGRONI: The real question is here - what is going on at Boeing? What's going on at Boeing? There's all sorts of symptoms; we need to see what is the illness.
SCHAPER: For his part at the Aspen Ideas Festival this week, Boeing CEO Dennis Muilenburg denied there's a safety culture problem.
(SOUNDBITE OF ARCHIVED RECORDING)
DENNIS MUILENBURG: Know that we have a commitment to excellence in our company in all of its dimensions. And I'll go back again to our relentless pursuit of safety.
SCHAPER: Neither Boeing nor the FAA would speculate on how long it could take for the company to develop a fix for this latest 737 Max problem. Airlines around the world have already had to park nearly 400 of the planes for more than four months now, costing them millions in lost revenue. Southwest is the biggest U.S. customer of the Max and has had to cancel close to 150 flights a day. It announced today it's pulling the 737 Max from its schedule through October 1. American and United have canceled Max flights through at least Labor Day.
David Schaper, NPR News, Chicago.
(SOUNDBITE OF MURCOF AND VANESSA WAGNER'S "AVRIL 14TH") Transcript provided by NPR, Copyright NPR.