737 MAX Groundings

The Boeing 737 MAX passenger airliner was grounded worldwide between March 2019 and December 2020longer in many jurisdictionsafter 346 people died in two crashes: Lion Air Flight 610 on October 29, 2018 and Ethiopian Airlines Flight 302 on March 10, 2019. The U.S. Federal Aviation Administration (FAA) resisted grounding the aircraft until March 13, 2019, when it received evidence of accident similarities. By then, 51 other regulators had already grounded the plane, and by March 18, 2019, all 387 aircraft in service were grounded.

In 2016, FAA approved Boeing's request to remove references to a new Maneuvering Characteristics Augmentation System (MCAS) from the flight manual. In November 2018, after the Lion Air accident, Boeing instructed pilots to take corrective action in case of a malfunction, when the airplane would enter a series of automated nosedives. Boeing avoided revealing MCAS until pilots requested further explanation. In December 2018, the FAA privately predicted that MCAS could cause 15 crashes over 30 years. In April 2019, the Ethiopian preliminary report stated that the crew had attempted the recovery procedure, and Boeing confirmed that MCAS had activated in both accidents.

FAA certification of the MAX was subsequently investigated by the U.S. Congress and multiple U.S. government agencies, including the Transportation Department, FBI, NTSB, Inspector General and special panels. Engineering reviews uncovered other design problems, unrelated to MCAS, in the flight computers and cockpit displays. The Indonesian NTSC and the Ethiopian ECAA both attributed the crashes to faulty aircraft design and other factors, including maintenance and flight crew actions. Lawmakers investigated Boeing's incentives to minimize training for the new aircraft. The FAA revoked Boeing's authority to issue airworthiness certificates for individual MAX airplanes and fined Boeing for exerting "undue pressure" on its designated aircraft inspectors.

In August 2020, the FAA published requirements for fixing each aircraft and improving pilot training. On November 18, 2020, the FAA ended the 20-month grounding, the longest ever of a U.S. airliner. The accidents and grounding cost Boeing an estimated $20billion in fines, compensation and legal fees, with indirect losses of more than $60 billion from 1,200 cancelled orders. The MAX resumed commercial flights in the U.S. in December 2020, and was recertified in Europe and Canada by January 2021.

Groundings

Accident investigations

ICAO regulations Annex 13, "Aircraft Accident and Incident Investigation", defines which states may participate in investigations. For the two MAX accidents these are:

# Indonesia, for Lion Air Flight 610 as the state of registration, state of occurrence, and state of the operator.
# Ethiopia, for Ethiopian Airlines Flight 302, as the state of registration, state of occurrence, and state of the operator.
# The United States, as the state of manufacturer and issuer of the type certificate.

The participating state or national transportation safety bureaus are the NTSB for the US and the NTSC for Indonesia. Australia and Singapore also offered technical assistance, shortly after the Lion Air accident, regarding data recovery from the new generation flight recorders (FDR). With the exception of Ethiopia, the officially recognized countries are members of the Joint Authorities Technical Review (JATR).

Lion Air Flight 610

Preliminary investigations revealed serious flight control problems that traumatized passengers and crew on the aircraft's previous flight, as well as signs of angle-of-attack (AoA) sensor and other instrument failures on that and previous flights, tied to a design flaw involving the Maneuvering Characteristics Augmentation System (MCAS) of the 737 MAX series. The aircraft maintenance records indicated that the AoA sensor was just replaced before the accident flight. The report tentatively attributed the accident to the erroneous angle-of-attack (AoA) data and automatic nose-down trim commanded by MCAS.

The NTSC final report, published on October 23, 2019, was prepared with assistance from the U.S. NTSB. NTSC's investigator Nurcahyo Utomo identified nine factors to the accident, saying:

"The nine factors are the root problem; they cannot be separated. Not one is contributing more than the other. Unlike NTSB reports that identify the primary cause of accidents and then list contributing issues determined to be less significant, Indonesia is following a convention used by many foreign regulators of listing causal factors without ranking them".

The final report has been shared with families of Lion Air Flight 610, then published on October 25, 2019.

Ethiopian Airlines Flight 302

On March 11, FAA defended the MAX against groundings by issuing a Continued Airworthiness Notice to operators. The initial reports for Flight 302 found that the pilots struggled to control the airplane in a manner similar to the Lion Air flight 610 crash. On March 13, 2019, the FAA announced that evidence from the crash site and satellite data on Flight 302 suggested that it might have suffered from the same problem as Lion Air Flight 610 in that the jackscrew controlling the pitch of the horizontal stabilizer of the crashed Flight 302, was found to be set in the full "nose down" position, similar to Lion Air Flight 610. This further implicated MCAS as contributory to the crash.

Ethiopian Airlines spokesman Biniyam Demssie said that the procedures for disabling MCAS had just been incorporated into pilot training. "All the pilots flying the MAX received the training after the Indonesia crash," he said. "There was a directive by Boeing, so they took that training." Despite following the procedure, the pilots could not recover.

The Ethiopian Civil Aviation Authority (ECAA) led investigations for Flight 302, and the United States Federal Aviation Administration assisted in the investigation. Both flight recorders (voice and data) were recovered from the crash site on March 11, 2019. The French aviation accident investigation agency BEA announced that it would analyze the flight recorders from the flight. BEA received the flight recorders on March 14, 2019.

On March 17, 2019, Dagmawit Moges, Ethiopia's transport minister, announced that the black box had been found and downloaded, and that the preliminary data retrieved from the flight data recorder show a "clear similarity" with those of Lion Air Flight 610 which crashed off Indonesia. Due to this finding, some experts in Indonesia suggested that the NTSC should cooperate with Flight 302's investigation team. Later on the evening, the NTSC offered assistance to Flight 302's investigation team, stating that the committee and the Indonesian Transportation Ministry would send investigators and representatives from the government to assist with the investigation of the crash.

The Ethiopian Civil Aviation Authority published an interim report on March 9, 2020, one day before the March 10 anniversary of the crash. Investigators have tentatively concluded that the crash was caused by the aircraft's design. , the final report has not yet been published, but there is an interim report available.

Timeline

2016

* March 2016, The General Manager of Boeing's 737 MAX program and the former Chief Project Engineer on the 737 MAX program both approved a redesign of MCAS to increase its authority to move the aircraft's stabilizer at low speed, in order to address "stall characteristics" requirements necessary for FAA certification. Just hours after the approval for MCAS's redesign was granted, Boeing sought, and the FAA approved, the removal of references to MCAS from Boeing's flight crew operations manual (FCOM). The FAA officials who authorized this request remained unaware of the redesign of MCAS until after the crash of the Lion Air flight.

2018

* January 10, The Operational Evaluation Report of the National Civil Aviation Agency of Brazil (ANAC) mentions the MCAS. The FAA had approved Boeing's request to remove MCAS from differences tables and quick reference handbook (QRH); The Operational Evaluation Report prepared by Transport Canada contained the same table as ANAC's, except the reference to MCAS.
* October 29, a 737 MAX 8 operating Lion Air Flight 610 crashed after take-off from Jakarta, killing all 189 on board. Boeing started redesigning the MCAS system right after the accident.
* November 6, Boeing issued an Operations Manual Bulletin (OMB), describing a MAX-specific feature of the pitch trim system, warning that with "erroneous data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds" which "can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after" and instructed pilots to counteract it by running the Runaway stabilizer and manual trim procedure. The background introduction of the bulletin states: "This bulletin directs flight crews to existing procedures to address this condition", and reminds operators to use the "existing procedures in the Runaway Stabilizer NNC on-Normal Conditions when the MAX reacts to a false stall detection. This was Boeing's first public announcement about MCAS, albeit not by name.
* November 7, the FAA issued an Emergency airworthiness directive to owners and operators, requiring revising the aircraft flight manual (AFM) "to provide the flight crew with runaway horizontal stabilizer trim procedures" when "repeated nose-down trim commands" are caused by "an erroneously high single AoA sensor", reinforcing the Boeing bulletin. The FAA directive warned that the problem was an "unsafe condition" that could result in "impact with terrain". The directive informs pilots of a new function specific to MAX models : "Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds." The FAA had removed reference to MCAS from its draft EAD.
* November 10, Boeing referred publicly for the first time to the MCAS by name in a Multi Operator Message to operators. The MCAS control law, a few lines of software code in the , could autonomously command nosedives, when even a single sensor failure resulted in bad data; MCAS was omitted from aircraft manuals and training, therefore flight crews had no knowledge of its existence or functioning until Boeing published a bulletin on November 6.
* November 27, the Allied Pilots Association of American Airlines had a meeting with Boeing to express concerns with the MCAS effectiveness, and was unnerved by the airframer's responses. Union president Daniel Carey later said, "The huge error of omission is that Boeing failed to disclose the existence of MCAS to the pilot community. The final fatal mistake was, therefore, the absence of robust pilot training in the event that the MCAS failed". The Boeing officials acknowledged that they were considering some changes, for example preventing MCAS's repetitive activation to ensure that it only triggers once.
* December 3, the FAA Seattle Certification Office reviewed an unpublished quantitative risk assessment analysis of the MAX, prepared using the "Transport Aircraft Risk Assessment Methodology" (TARAM). The U.S. House Committee on Transportation and Infrastructure made the report public just over a year later, on December 11, 2019. In the committee's words, the report concluded that "if left uncorrected, the MCAS design flaw in the 737 MAX could result in as many as 15 future fatal crashes over the life of the fleet", predicting 2900 deaths over 30 years.
* December 17, in a presentation to the FAA, Boeing deflected blame and continued to assert that appropriate crew action would save the aircraft.

2019

* March 10, another 737 MAX 8 operating Ethiopian Airlines Flight 302 crashed shortly after take-off from Addis Ababa airport, killing all 157 on board, due to a similar faulty MCAS, initiating a worldwide flight ban for the aircraft, starting with China on March 11. This was followed in quick succession the following day, March 12 by Singapore, India, Turkey, South Korea, the European Union, Australia and Malaysia. See timeline and list of groundings by other countries & regions. The US FAA issued an affirmation of the continued airworthiness of the 737 MAX.
* March 13, the U.S. FAA was among the last to order the grounding of the 737 MAX, after claiming there was no reason: China had the most aircraft in service, 96, followed by the U.S. with 72, Canada with 39 and India with 21. The FAA issued an Emergency Order of Prohibition grounding Boeing 737 MAX airplanes, followed by a CANIC.
* March 20, EASA and Transport Canada indicated that they would conduct their own reviews of Boeing's proposed software update.
* March 27, Boeing unveiled a software update to avoid MCAS errors, which was pending certification after already being developed and tested in-flight.
* April 5, Boeing announced it was cutting 737 production by almost a fifth, to 42 aircraft monthly, anticipating a prolonged grounding, and had formed an internal design review committee.
* May 13, Republican Congressman Sam Graves at the House Aviation subcommittee hearing, blamed the 737 MAX crashes on poor training of the Indonesian and Ethiopian pilots; he stated that "pilots trained in the U.S. would have been successful" in handling the emergencies on both jets.
* June 18, IAG signed a letter of intent for 200 737 MAXs at the Paris air show, followed by Turkish SunExpress and Air Astana later in the year.
* June 26, flight tests for the FAA uncovered a data processing issue affecting the pilots' ability to perform the "runaway stabilizer" procedure to respond to MCAS errors.
* October 30, Boeing CEO Dennis Muilenburg testified before U.S. Congress committees, defending Boeing's safety culture and denying knowledge of internal messages in which Boeing's former chief technical pilot said he had unknowingly lied to regulators, and voiced his concerns on MCAS.
* November 22, Boeing unveiled the first 737 MAX 10 flight-test aircraft.
* November 26, the FAA revoked Boeing's Organization Designation Authorization to issue airworthiness certificates for individual MAX airplanes.
* December 17, Boeing confirmed the suspension of 737 MAX production from January 2020.
* December 23, Dennis Muilenburg resigned, to be replaced by board chairman David Calhoun.

2020

* January 7, Boeing recommended "simulator training in addition to computer based training".
* January 9, Boeing released previous messages in which it claimed no flight simulator time was needed for pilots, and distanced itself from emails mocking airlines and the FAA, and criticizing the 737 MAX design.
* January 13, David Calhoun became CEO, pledging to improve Boeing's commitment to safety and transparency, and estimating the return to service in mid-2020.
* January 21, Boeing estimated the ungrounding could begin in mid-2020.
* May 27, Boeing resumed production of the MAX at a "very gradual pace".
* June 28 to July 1, the FAA conducted flight tests with a view to recertification of the 737 MAX.
* September 16, the U.S. House of Representatives releases its concluding report, blaming Boeing and the FAA for lapses in the design, construction and certification.
* September 30, a Boeing 737 MAX test aircraft was flown by FAA administrator Stephen Dickson.
* October 16, Patrick Ky, the executive director of the European Union Aviation Safety Agency, claimed that the updated 737 MAX reached the level of safety "high enough" for EASA.
* November 18, the FAA issued a CANIC, subject to mandatory updates on each individual aircraft. Other regulators were expected to follow.
* December 9, Brazilian low-cost carrier Gol Transportes Aéreos was the first airline to resume passenger service.
* December 29, American Airlines was the first US airline to resume commercial operations.

2021

*January 7, Boeing settled to pay over $2.5 billion after being charged with fraud over the company's hiding of information from safety regulators: a criminal monetary penalty of $243.6 million, $1.77 billion of damages to airline customers, and a $500 million crash-victim beneficiaries fund.
*January 13, the Trinidad and Tobago Civil Aviation Authority authorized the MAX to resume flights in Trinidad and Tobago's airspace.
*January 18, Transport Canada authorized the MAX to resume flights in Canadian airspace. Canadian operators must modify the aircraft to enable pilots to disable the stick shaker when it is erroneously activated, if they are certain that they understand the underlying cause.
* January 27, EASA cleared the MAX to resume service in Europe, subject to additional restrictions similar to those mandated by Transport Canada. Certain approaches requiring precision navigation were however not yet approved as EASA was awaiting data from Boeing as to the aircraft's ability to maintain the required performance in the event of sensor failures.
* February 26, the Australian Civil Aviation Safety Authority lifted its ban on the MAX, accepting the return-to-service requirements set by the FAA. Australia was the first nation in the Asia-Pacific region to clear the aircraft to return to service.
*April 9, Boeing announces that it has notified 16 airlines and the FAA of a potential electrical problem. Boeing refused to say how many planes were affected but four airlines grounded nearly 70 MAX aircraft.
*August 26, the Indian Directorate General of Civil Aviation rescinds its ban on MAX airplanes in India on the condition that they meet the requirements set by the FAA and EASA.
*September 2, Boeing and Ethiopian Airlines reach an undisclosed out-of-court settlement, with Ethiopian Airlines announcing that the MAX could return to service in January 2022. The same day, the Civil Aviation Authority of Malaysia rescinded its ban on the MAX.
*October 14, federal prosecutors indict former Boeing pilot Mark Forkner for fraud, stating he lied to the FAA in an attempt to obtain money from customers. Forkner is the first person to receive criminal charges in the investigation.
* December 2, China's civil aviation regulator cleared the 94 jets stored by 11 carriers in China to fly again, before resuming deliveries in early 2022 of the ~ planes currently stored by Boeing, as over 180 countries out of 195 have lifted the grounding. However, the Civil Aviation Administration of China does not give a date as to when the aircraft can begin passenger operations.
*December 28, Indonesia's ministry of transport removes its ban on the MAX.

2022

* February 1, Ethiopian Airlines cleared the MAX to return to service, with a demonstration flight being held the same day.

Type certification and return to service

Maneuvering Characteristics Augmentation System

MCAS on the 737 MAX was designed to mimic the pitching behavior of the previous generation of the series, the Boeing 737 NG, by pushing down the aircraft nose from an elevated angle of attack (AoA) by automatically adjusting the horizontal stabilizer and trim tab. The system was intended to protect pilots from inadvertently flying at too steep an angle, which could result in a stall. Boeing, however, asserted that MCAS was not an anti-stall system, as the media widely reported it to be. Pilot movement of the control column on the MAX did not disable MCAS, unlike an earlier implementation of MCAS on the U.S. Air Force Boeing 767 Tanker. During certification of the MAX, Boeing requested and received permission from the FAA to remove a description of MCAS from the aircraft manual, leaving pilots unaware of the system when the airplane entered service in 2017. Boeing had also knowingly withheld knowledge, for at least a year before the Lion Air crash, that a system to warn of a possible AoA malfunction did not work as advertised.

On November 6, 2018, Boeing published a supplementary service bulletin prompted by the first crash. The bulletin describes warnings triggered by erroneous AoA data could cause the pitch trim system to repeatedly push down the nose of the airplane and referred pilots to a "non-normal runaway trim" procedure as resolution, specifying a narrow window of a few seconds before the system would reactivate and pitch the nose down again. The FAA issued an emergency airworthiness directive, 2018-23-51, on November 7, 2018, requiring the bulletin's inclusion in the flight manuals, and that pilots immediately review the new information provided. Pilots wanted to know more about the issue, and Boeing responded by publicly naming MCAS for the first time in another message to airlines, noting that MCAS operates "without pilot input."

In December 2018, the FAA had privately predicted that 15 MCAS-related accidents could result if the system was not redesigned. Boeing said it would revise MCAS software by April 2019 to correct any problems. The study was only revealed a year later at the December 2019 House of Representatives hearing. Stephen Dickson, who became FAA administrator during the accident investigations, testified at the hearing about his agency's response after the Lion Air accident, saying "the result was not satisfactory".

After the March 2019 crash of Ethiopian Airlines Flight 302, Ethiopian investigators determined that pilots had attempted the recommended recovery procedure. Boeing admitted that MCAS played a role in both accidents by activating when it received faulty data from an exterior AoA sensor.

In 2020, an FAA Airworthiness Directive approved design changes for each MAX aircraft, requiring input from two AoA sensors for MCAS activation, elimination of the system's ability to repeatedly activate, and allowing pilots to override the system if necessary. Boeing also overhauled the computer architecture of the flight controls to provide greater redundancy. For each aircraft, the FAA would issue the airworthiness certificate, without delegation to Boeing, upon completion of an AoA sensor system test and a validation test flight. The FAA also required that all MAX pilots receive MCAS-related training in flight simulators by 2021. Before the accidents, simulator training on the MAX was not required, because the FAA accepted Boeing's position that the MAX was sufficiently similar to the previous 737 series, the NG.

Reactions

Financial and economic effects

The have had a deep financial effect on the aviation industry and a significant effect on the national economy of the United States. No airline took delivery of the MAX during the groundings. Boeing slowed MAX production to 42 aircraft per month and halted MAX production from January to May 2020. Boeing suffered directly through increased costs, loss of revenue, reputational damage, victim litigation, client compensation, reduced credit rating, and decreased stock value. In January 2020, the company estimated a loss of $18.4 billion for 2019, and it reported 183 canceled MAX orders for the year.

In February 2020, the COVID-19 pandemic and resulting travel bans created further uncertainty for Boeing. In March 2020, news that Boeing was seeking a $60 billion bailout caused a steep drop in its stock price, though Boeing eventually received $17 billion in funds from the coronavirus stimulus. Its extensive supply chain providing aircraft components and flight simulators suffered similar losses, as did the aircraft services industry, including crew training, the aftermarket, and the aviation insurance industry. Major flight simulator supplier CAE increased production of simulators for the Boeing 737 MAX in anticipation of a jump in demand for pilot training in November 2019. At the time of the recertification by the FAA in November 2020, Boeing's net orders for the 737 MAX were down by more than 1,000 aircraft, 448 orders canceled and 782 orders removed from the backlog because they are no longer certain enough to rely on; the total estimated direct costs of the MAX groundings were US$20billion and indirect costs over US$60billion. On January 7, 2021, Boeing settled to pay over $2.5 billion after being charged with fraud.

Popular culture

In September 2021, Frontline PBS released "Boeing's Fatal Flaw", a documentary about how Boeing ignored critical safety issues with the 737 MAX resulting in the crash of two airliners.

In February 2022, Netflix released '' Downfall: The Case Against Boeing'', a documentary about the two plane crashes directed by Rory Kennedy.

See also

* Qantas Flight 72: data failure causing pitch down, severely injuring passengers
* Air France Flight 447: fatal accident following data and pitot tube failure and autopilot disablement
* Turkish Airlines Flight 1951: Dutch authorities have reopened the accident probe into this 2009 accident involving the prior generation 737-800 series aircraft.
* Boeing 787 Dreamliner battery fires: the aircraft was grounded in 2013 for modifications to mitigate or contain the risk of inflight fire.
*Boeing 737 rudder issues

Notes

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