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The Boeing 737 MAX is still flying worldwide—despite mounting evidence that the aircraft is unsafe.

Investigation reports from the Indonesian and Ethiopian governments on the Boeing 737 MAX crashes in 2018 and 2019 indicate that both of those brand-new planes had preexisting defects that have yet to be resolved. The Ethiopian investigators also concluded that production quality issues played a pivotal role in these disasters. The U.S. government’s egregious failure to acknowledge this key fact puts countless more passengers at risk—and is a slap in the face to the families of the 346 victims, who deserve to know the truth.

By Ed Pierson Published January 13, 2023

Ask almost anyone what caused two Boeing 737 MAX planes to crash moments after takeoff in 2018 and 2019, and they’ll likely say what has been repeatedly parroted by the media and U.S. government agencies: a software malfunction. This theory, expertly peddled by Boeing’s public relations army, is a narrative that regulators have been content to support. But in reality, a wealth of evidence shows this malfunction was only partly to blame.

There is no doubt that flawed software was a contributing factor in these tragedies. But it is now well documented that the implicated Maneuvering Characteristics Augmentation System (MCAS) software that repeatedly pitched the planes downward was triggered in both crashes by the failure of an Angle of Attack (AOA) sensor—a three-pound component of the 737 MAX’s highly interconnected flight control system.

To close the case after focusing almost solely on the software malfunction is to completely ignore a question that virtually screams from the Indonesian and Ethiopian governments’ reports on the accidents: Why did the AOA sensor fail in each of these airplanes? This vital question has not been satisfactorily answered by Boeing or by U.S. investigators, meaning the root causes of the 737 MAX crashes have not been fully addressed—endangering the flying public.

On December 23, 2022, the Ethiopian Aircraft Accident Investigation Bureau released its 331-page final report on the crash of the Ethiopian Airlines plane. The report concludes the AOA sensor on flight ET302 failed due to production quality defects. It further emphasizes that the crashed Indonesian and Ethiopian planes both displayed defects and anomalies before their fatal flights, and details “intermittent flight control system abnormalities [that] began well before the accident flight.”

According to the report, these issues on the Ethiopian plane began to occur in December 2018 "when the airplane was one month old" and included "several pilot write ups involving temporary fluctuations of vertical speed and altitude.” There were three cases of the “airplane rolling during autopilot operation,” and “altitude and vertical speed indications on the PFD (Primary Flight Display) showed erratic and exaggerated indications.”

The Ethiopian report further states: “MCAS and the lack of pilot training did not trigger the accident; … it was the failure of the sensors due to the production quality defects. If the intermittent defects did not cause the AOA sensors to fail on the accident flight, MCAS would not have activated, and these two accidents would not have occurred.”

Immediately after the release of the Ethiopian report, the U.S. National Transportation Safety Board (NTSB) issued a press release critiquing it, stating that there is no evidence the AOA sensor failed because of a production problem. Rather, based on an analysis by the manufacturer of the sensor, the NTSB press release asserts the sensor could only have failed due to a bird strike.

I was a Senior Manager at Boeing’s 737 factory in Renton, Washington. Months before the 737 MAX disasters, I had serious concerns that process breakdowns and quality defects could lead to exactly the kinds of safety hazards in the planes’ critical systems referenced in the Ethiopian report.

Airplanes must be constructed in a specific order, as set out by the FAA. But the 737 factory was plagued by supply chain issues and unrelenting schedule pressure, and many parts were delivered to the Boeing factory chronically late; without them, workers couldn’t build their section of the plane. This had a cascading effect, because the next workers down the line couldn’t build their section if the preceding components weren’t installed. To meet production targets, planes were assembled “out of sequence,” and workers put in extensive overtime—two big safety flags, as rushing and overwork increase the probability of human error.

Electrical wiring was another critical concern. The Electrical Wiring Interconnect System (EWIS) is the electrical infrastructure of an airplane. MAX airplanes have over 50 miles of wiring; if a technician is rushing, errors can easily be made in the installation. Prior to the crashes, I reported on electrical installation and testing process breakdowns that are directly relevant to the system failures subsequently seen, as any number of EWIS failures could have caused anomalies like those described in both the Indonesian and Ethiopian accident reports.

Unbeknownst to me, the Lion Air airplane was in our production system at the time I brought my concerns to the senior leader of the 737 program. I strongly advised shutting down the factory, but my concerns and recommendations were disregarded. Then, in October 2018, the Lion Air airplane crashed. The production and wiring issues I was flagging, as noted above, have particular relevance to the cause of that disaster. After weeks of troubleshooting electrical and flight control issues in that plane, the airline replaced one of its Angle of Attack sensors. The two-month-old plane crashed the next day.

Lion Air investigators concluded the unrecovered replacement sensor was to blame because it had been miscalibrated—providing an inaccurate measurement—and may have been installed improperly. However, post-accident testing of the original Boeing-installed sensor from that plane revealed defects pointing to production quality issues. For example, two different wires had been epoxied together, resulting in electrical arcing inside the sensor; this is dangerous because arcing can lead to fires, explosions, and system malfunctions.

After the Lion Air crash, I brought the details of my urgent concerns about the numerous production problems higher up the chain, to the attention of Boeing’s CEO, General Counsel, and Board of Directors. But again, production continued. Then in March 2019, the Ethiopian Airlines plane went down. Seeing the prospect of further disasters, I made urgent pleas to the NTSB, Federal Aviation Administration (FAA) and Department of Transportation (DOT). I was stunned when the NTSB—the lead accident investigator in the United States—told me the issues I’d raised fell outside the scope of its role as “Accredited Representative” in the 737 MAX investigations, because the NTSB was just assisting the investigation.

The NTSB concluded the ET302 plane went down due to a bird striking the same AOA sensor previously implicated in the Lion Air flight JT610 crash. The Ethiopian report challenged the NTSB’s theory as to why the sensor failed, stating: “A miscalibrated sensor scenario for JT610 and a bird strike scenario for ET302 cannot explain the flight control system alerting, maintenance messages and electrical/electronic system faults that were occurring on these airplanes in the weeks and days before their accidents.” They went further, asserting, “These accidents were triggered by production quality defects that presented as intermittent system malfunctions.”

The answer to the sensor failure question is important, because production defects mean similar unresolved defects could be on other planes currently flying. To illustrate, the following production quality defects have been discovered in 737 MAX airplanes since the crashes: defective slat tracks on wings, foreign object debris inside fuel tanks, removal of lightning protection around engines, improper installation of fuel sealant (which could lead to fuel leaks), installation of defective motors for the horizontal stabilizer that controls the airplane’s pitch, and faulty electrical bonding and grounding (which could result in loss of critical functions, which could in turn compromise safety in flight and landing).

The public safety threat, Boeing's deceit, and government inaction drove me to testify before the U.S. Congress in 2019 as the “Boeing whistleblower.” Congress, in turn, demanded and received promises to investigate the 737 factory to determine the role production issues played in the crashes. The NTSB made numerous promises to the victims’ families, the public, Congress, aviation regulators, and airlines around the world to fully cooperate with international investigators and provide technical assistance, with the primary goal of preventing another crash. Yet, despite clear evidence of production quality defects and other serious production problems, in a May 21, 2022 email to me and a mother who lost her daughter on flight ET302, the NTSB admitted it did not investigate the 737 factory.

This stunning revelation should shock anyone who is considering stepping onto a 737 MAX or putting a loved one on this plane. As a party to the international investigations, the NTSB has a responsibility to share all relevant information that would aid in determining the cause of these disasters. How is it that the NTSB has failed to look into the production issues that have been flagged to them over and over again?

Make no mistake: Boeing was aware of the production quality risks before the two disasters occurred. They were duly warned, and grossly negligent. In fact, before the disasters, Boeing had quietly eliminated thousands of quality-control inspections on every 737 MAX plane, essentially making factory employees self-inspect and self-certify their work. This extremely dangerous, financially driven program was named “Verification Optimization”. It was a hazardous departure from prior quality-control standards that had required an inspector’s sign-off. Fewer inspections mean more planes can be built and sold in less time, increasing profits. Boeing's International Association of Machinists Union has been fighting this misguided program ever since they were first informed about it in the days after the Lion Air crash. Thanks to persistent union efforts, Boeing is reinstating many of the inspections, but what is the plan for the hundred of planes that left the factory without those inspections?

The MAX airplane has been “recertified” by the FAA, and more than 900 of these planes are now flying around the world. Alarmingly, one U.S. airline with 35 new MAX planes delivered in 2021-22 submitted a whopping 425 malfunction reports in the past year alone. Even more alarming than the quantity is the content. Many of those reports describe intermittent safety issues in flight systems with multiple components. These were difficult for maintenance personnel to duplicate or to troubleshoot conclusively—classic signs of electrical or electronic defects. A few examples of incidents in the past two months alone: electrical arcing cracked a pilot’s window, an autothrottle failed on takeoff, electrical arcing shattered another pilot’s window, and flight management computers suffered a dual failure.

Boeing is quick to tout impressive performance metrics using “big data” statistics such as millions of miles safely flown or hundreds of thousands of safe departures. But these metrics can mask an individual airplane’s actual condition. And there is no way to confirm the accuracy of Boeing’s statistics, because there is no publicly available systems malfunction data for airlines flying the 737 MAX outside the United States.

It is time for the NTSB to follow the evidence outlined in the Indonesian and Ethiopian accident reports and to prevent yet another tragedy by examining and addressing the multitude of issues described above. 737 MAX airplanes need to be grounded until the electrical and electronic defects are fixed. DOT Secretary Pete Buttigieg needs to get involved to ensure the FAA revamps their oversight of Boeing factories and that incident reports are properly investigated and root causes resolved.

Everyone who flies is trusting the U.S. authorities to do everything possible to make sure their plane, and the plane they put their loved ones on, will land safely. More must be done to ensure that not one more life is lost, if it is in our power to prevent it. At the very least, we owe this to the people who lost their lives in these preventable disasters, and to their families.

Ed Pierson is a safety advocate and keynote speaker. He is the Boeing whistleblower who testified before the U.S. Congress during investigations into the Boeing 737 MAX accidents and has authored three reports on these tragedies. In his 10 years at Boeing, he served as a Flight Operations Senior Manager in Boeing’s Test and Evaluation organization—the division responsible for flight testing all aircraft—and then as a Senior Manager at the 737 factory, where he oversaw production system support for the 737 MAX and the military variant P-8 Poseidon, before retiring in 2018. Mr. Pierson also served in active and reserve roles in the U.S. Navy for 30 years, holding several leadership positions, including Squadron Commanding Officer, Leadership & Ethics Instructor, and Operations Center Director. He was recently selected to serve as a board member for FlyersRights. Mr. Pierson is a graduate of George Mason University, the U.S. Naval Academy, and Naval Flight School.

Boeing and the NTSB declined to comment on this article.

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