Boeing 737 MAX groundings

In March 2019, aviation authorities worldwide grounded the Boeing 737 MAX passenger airliner after 346 people died in two plane crashes, Lion Air Flight 610 on October 29, 2018 and Ethiopian Airlines Flight 302 on March 10, 2019. Investigators determined that a new automated flight control, the Maneuvering Characteristics Augmentation System (MCAS) malfunctioned on both flights, sending each plane into repeated nosedives. Boeing had omitted the system from crew manuals and training. In November 2018, a week after the first accident, Boeing and the U.S. Federal Aviation Administration (FAA) sent airlines updated procedures for crews to disable MCAS if it malfunctioned. In December 2018, the FAA predicted more accidents if MCAS was not revised, but kept its findings private and believed the advisories to airlines sufficed until Boeing developed a permanent solution.

Boeing 737 MAX groundings
A parking lot at Boeing Field in Seattle, Washington, filled with undelivered Boeing 737 MAX aircraft
Date
  • Lion Air accident: October 29, 2018
  • Ethiopian Airlines accident: March 10, 2019
  • First grounding: March 10, 2019 (2019-03-10) by Ethiopian Airlines
  • Effectively a worldwide grounding: March 13, 2019 (2019-03-13) by the Federal Aviation Administration (FAA)
Duration
  • between accidents: 4 months and 10 days
  • of grounding: 1 year, 1 month and 16 days since March 10, 2019 (413 days ago)
CauseAirworthiness revoked after recurring flight control failure
Deaths346:
  • 189 on Lion Air Flight 610
  • 157 on Ethiopian Airlines Flight 302

On March 10, 2019, the day of the second crash, Ethiopian Airlines grounded its remaining MAX fleet. On March 11, the Civil Aviation Administration of China ordered the first nationwide grounding, followed by most other regulators in quick succession. The FAA publicly affirmed the airworthiness of the airplane on March 11, then grounded it on March 13 after receiving evidence of accident similarities. By March 18, all 387 airplanes, which served 8,600 flights each week for 59 airlines, were grounded worldwide. Boeing suspended MAX deliveries to airlines, but produced another 400 of the aircraft before halting manufacturing in January 2020.

During the groundings, the FAA certification of the MAX was investigated by the U.S. Congress, Transportation Department, FBI and ad hoc panels, which questioned whether the FAA's delegation of authority weakened its oversight of Boeing. In addition to problems with MCAS, several systems and manufacturing defects were also uncovered.

Investigators published their findings on the first anniversaries of the accidents in October 2019 and March 2020. The Indonesian NTSC faulted airplane design, certification, maintenance, and flight crew actions. The Ethiopian ECAA, which determined that the flight crew had attempted the recovery procedure, assigned blame to the aircraft's software design. The U.S. NTSB concluded that malfunctions resulted in multiple cockpit alerts that likely confused the flight crews. The U.S. House of Representatives criticized Boeing's "culture of concealment" during certification and in the aftermath of both accidents. As a result, Boeing reversed its policy and recommended flight simulator training for all MAX pilots. The longest ever grounding of a U.S. airliner was estimated to cost Boeing $18.6 billion by March 2020, and is subject to indefinite delays caused by the coronavirus pandemic. By April 2020, airlines and lessors cancelled nearly 200 orders for the MAX.

Timeline
  • On October 29, 2018, a 737 MAX 8 operating Lion Air Flight 610 crashed after take-off from Jakarta, killing 189 people.
  • On November 6, 2018, Boeing issued a service bulletin warning that with "erroneous AOA 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.[1]
  • On November 7, the FAA issued an Emergency airworthiness directive requiring revising "the 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".[2]
  • On November 10, Boeing referred to MCAS in multi-operator messages.[3] The automated flight control could cause unintended nosedives, but was omitted from crew manuals and training.[4]
  • On November 27, the Allied Pilots Association of American Airlines had a meeting with Boeing to express concerns with the MCAS effectiveness, but was unnerved by the airframer responses.[5]
  • On December 3, the FAA conducted an unpublished "Transport Aircraft Risk Assessment Methodology” (TARAM) analysis that concluded, "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”; it was exposed by the United States House Committee on Transportation and Infrastructure on December 11, 2019.[6]
  • On March 10, 2019, 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 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.
  • On March 27, Boeing unveiled a software update to avoid MCAS errors, already developed and tested it in-flight, to be certified.
  • On 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.
  • On June 18, IAG committed to the 737 MAX with a letter of intent for 200 at the Paris air show, followed by Turkish SunExpress and Air Astana later in the year.
  • On June 26, flight tests for the FAA uncovered a data processing issue affecting the pilots' ability to perform the "runaway stabiliser" procedure to respond to MCAS errors.
  • On 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 its concerns on MCAS.
  • On November 22, Boeing unveiled the first 737 MAX 10 flight-test aircraft.[4]
  • On November 26, the FAA revoked Boeing's Organization Designation Authorization to issue airworthiness certificates for individual MAX airplanes.[7]
  • On December 17, Boeing confirmed the suspension of 737 MAX production from January 2020.
  • On December 23, Dennis Muilenburg resigned, to be replaced by board chairman David Calhoun.[4]
  • On January 7, 2020, Boeing recommended "simulator training in addition to computer based training".[8]
  • On 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 criticising the 737 MAX design.
  • On 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.
  • On January 21, Boeing estimated the ungrounding could begin in mid-2020.[4]

Groundings

After the Ethiopian Airlines crash, China and most other aviation authorities preceded the U.S. Federal Aviation Administration (FAA), the certifying agency for the MAX, in grounding the airliner over perceived safety risks. The FAA issued a Continued Airworthiness Notification to the International Community on March 11 and resisted pressure from U.S. lawmakers to ground the aircraft.[9][10] Boeing CEO Dennis Muilenburg called U.S. president Trump on March 12 to assure him the airplane was safe.[11] On March 13, 2019, the FAA found similarities between the two accidents and grounded the plane.[12] About 30 MAX aircraft were flying in U.S. airspace at the time and were allowed to reach their destinations.[13] By March 18, regulators grounded all 387 MAX aircraft in service with 59 airlines worldwide and making 8,600 flights each week.[14] Several ferry flights were operated with flaps extended to circumvent MCAS activation.

The grounding subsequently became the longest ever of a U.S. airliner.[15] As of January 2020, another 400 newly-manufactured aircraft await delivery to airlines pending the aircraft's return to service.

Accident investigations

Lion Air Flight 610
PK-LQP, the aircraft involved in the crash of 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.[16] The report tentatively attributed the accident to the erroneous angle-of-attack (AoA) data and automatic nose-down trim commanded by MCAS.[17][18]

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".[19][20][21]

The final report has been shared with families of Lion Air Flight 610, then published on October 25, 2019.[22][23][24][25]

Ethiopian Airlines Flight 302
ET-AVJ, the Ethiopian Airlines aircraft that crashed as Flight 302

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.[26] 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.[27] This further implicated MCAS as contributory to the crash.[28][29][30]

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."[31] Despite following the procedure, the pilots could not recover.[32]

The Ethiopian Civil Aviation Authority (ECAA) is leading investigations for Flight 302. The United States Federal Aviation Administration will also assist in the investigation.[33] Both the cockpit voice recorder and the flight data recorder were recovered from the crash site on March 11, 2019.[34] The French aviation accident investigation agency BEA announced that it would analyze the flight recorders from the flight.[35] BEA received the flight recorders on March 14, 2019.[36]

On March 17, 2019, the Ethiopia's transport minister Dagmawit Moges 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.[37][38][39] Due to this finding, some experts in Indonesia suggested that the NTSC should cooperate with Flight 302's investigation team.[40] 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.[41]

The Ethiopian Civil Aviation Authority published an interim report on March 9, 2020, one day before the March 10 anniversary of the crash.[42] Investigators have tentatively concluded that the crash was caused by the aircraft's design.[43][44]

United States
The vertical airspeeds of the Boeing 737 MAX 8s involved in the JT 610 and ET 302 crashes

On November 6, 2018, four days before it identified MCAS by name, Boeing published a supplementary service bulletin prompted by the first crash. The bulletin describes warnings triggered by erroneous AoA data, 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.[45] 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.[46][47] On March 11, FAA defended the aircraft against groundings citing these emergency procedures (Continued Airworthiness Notification to the International Community) for operators.

In December 2018, a month after the Lion Air accident, the FAA had conducted an internal safety risk analysis predicted fifteen more crashes with no repairs to MCAS, but that report was not revealed until the U.S. House hearing in December 2019. FAA's administrator, Stephen Dickson, who assumed the position during the accident investigations, said in retrospect that the accident risk was unsatisfactory.

On September 26, 2019, the NTSB released the results of its review of potential lapses in the design and approval of the 737 MAX.[48][49](p1)[50] The NTSB report concludes that assumptions "that Boeing used in its functional hazard assessment of uncommanded MCAS function for the 737 MAX did not adequately consider and account for the impact that multiple flight deck alerts and indications could have on pilots' responses to the hazard". When Boeing induced a stabilizer trim input that simulated the stabilizer moving consistent with the MCAS function, "... the specific failure modes that could lead to unintended MCAS activation (such as an erroneous high AOA input to the MCAS) were not simulated as part of these functional hazard assessment validation tests. As a result, additional flight deck effects (such as IAS DISAGREE and ALT DISAGREE alerts and stick shaker activation) resulting from the same underlying failure (for example, erroneous AOA) were not simulated and were not in the stabilizer trim safety assessment report reviewed by the NTSB."[49][49][51]

The NTSB questioned the long-held industry and FAA practice of assuming the nearly instantaneous responses of highly trained test pilots as opposed to pilots of all levels of experience to verify human factors in aircraft safety.[52] The NTSB expressed concerns that the process used to evaluate the original design needs improvement because that process is still in use to certify current and future aircraft and system designs. The FAA could for example randomly sample pools from the worldwide pilot community to get a more representative assessment of cockpit situations.[53]

Responsible states

ICAO regulations Annex 13, “Aircraft Accident and Incident Investigation”, defines which states may participate in investigations. For the two MAX accidents these are:[54]

  1. Indonesia, for Lion Air Flight 610 as state of registration, state of occurrence and state of operator.
  2. Ethiopia, for Ethiopian Airlines Flight 302, as state of registration, state of occurrence and state of operator.
  3. The United States, as 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 recognised countries are members of the Joint Authorities Technical Review (JATR).

Type certification and return to service
The Boeing 737 MAX needs to be recertified to fly again

On March 11, 2019, a U.S. federal grand jury issued a subpoena on behalf of the U.S. Justice Department (DOJ) for documents related to development of the 737 MAX.[55][56][57][58] On March 19, 2019, the U.S. Department of Transportation requested the Office of Inspector General to conduct an audit on the 737 MAX certification process.[59] Under a system known as the Organization Designation Authorization, the FAA allowed manufacturers like Boeing to act on its behalf, while the agency retains legal authority to issue a type certificate. The goal for Boeing was to ensure the aircraft retains a compatible type rating with all other aircraft in the 737 family, thus avoiding costly simulator training and the need to learn about new systems like the MCAS.

Over the next several months, The Seattle Times's coverage of the ongoing crisis revealed how management decisions at Boeing and the FAA pushed for cost-saving solutions, but ultimately produced a flawed design with insufficient oversight. [60]

In November 2019, the FAA suspended Boeing's authority to issue individual airworthiness certificates for MAX aircraft. In February 2020, the DOJ was conducting an ongoing investigation into whether Boeing lied to the FAA.[61] In March 2020, the House of Representatives criticized Boeing's culture of concealment and its undue influence over the FAA, as exemplified during certification and in the aftermath of the crashes.

By convention, aviation regulators worldwide accept the certification of aircraft from the country of manufacture and do not review those certifications in much detail.[62] However, since the fatal accidents and grounding of 737 MAX several aviation authorities, particularly the European EASA, will conduct their assessments and validation tests of the MAX prior to authorizing it in their controlled airspace. As of October 2019 the disagreements over various system revision details, Level of Involvement (LoI) between the two leading aviation authorities, FAA and EASA, as well as Boeing's new recommendation of simulator training could delay the 737 MAX return to service.[63]

Maneuvering Characteristics Augmentation System
The MAX uses an adjustable stabilizer, moved by a jackscrew, to provide the required pitch trim forces. Generic stabilizer illustrated.

The Maneuvering Characteristics Augmentation System (MCAS) is a flight control law (software) embedded into the Boeing 737 MAX flight control system which attempts to mimic pitching behavior similar to aircraft in the previous generation of the series, the Boeing 737 NG. When MCAS detects that the aircraft is operating in manual flight, with flaps up, at an elevated angle of attack (AoA), it adjusts the horizontal stabilizer trim to add positive force feedback (a "nose heavy" feel), through the control column, so the pilot will not inadvertently pull the airplane up too steeply, potentially causing a stall. Contrary to descriptions in news reports, however, Boeing claims that MCAS is not an anti-stall system. Stabilizer movement commanded by MCAS pushes down the nose of the airplane automatically without pilot input.

MCAS on the MAX was designed to activate using input from only one of the airplane's two angle of attack sensors, making the system susceptible to a single point of failure. Boeing omitted a description of MCAS from MAX flight manuals, leaving pilots unaware of the system when the airplane entered service.[64] In April 2019, Boeing admitted that MCAS played a role in the fatal crashes of Lion Air Flight 610 and Ethiopian Airlines Flight 302. The first time Boeing publicly revealed the existence of MCAS on the 737 MAX was in a message to airline operators and other aviation interests on November 10, 2018, twelve days after the Lion Air crash.[65] Boeing had also been aware of other software issues that suppressed a crucial AoA disagree message. With no knowledge of MCAS and its behavior, the pilots of the Lion Air flight, the first to crash, were at a disadvantage when attempting to respond to the system's erroneous activation. Procedures emphasized by Boeing and the FAA did not prevent the later Ethiopian Airlines crash, which led to the worldwide grounding of the airliner.

MCAS was first deployed on the Boeing KC-46 Air Force tanker, where it "similarly moves the stabilizer in a wind-up turn".[66] Unlike the 737 MAX, however, MCAS could be overridden on the KC-46 by pulling back on its control column. The Wall Street Journal reported in May 2019 that Boeing failed to share information about that issue for "about a year" before the Lion Air crash in Indonesia.[67]

Reactions

After the Boeing 737 MAX groundings, reactions came from multiple organizations. Boeing initially expressed its sympathy to the relatives of the Lion Air Flight 610 and Ethiopian Airlines Flight 302 crashes victims, but defended the aircraft against any faults until disproven by evidence. Boeing provided several outdated return to service timelines, the soonest of which was "in the coming weeks" following the grounding. Public observers commented upon the "cozy relationship" that exists between the industry and its regulators.

After Boeing's crisis management failed to appease stakeholder concerns with the aircraft, the board removed Dennis Muilenburg as chairman and replaced him with David L. Calhoun on October 11, 2019. Airbus, its main competitor, is unwilling to put the blame on Boeing's engineering as the certification process could be more difficult for every airframer, and its production capacities are already maximized.

Pilots and flight attendants opinions are mixed as some expressed confidence in the certification renewal, while others are disappointed as Boeing had hidden an important safety feature to their knowledge. Most airlines seek compensation from Boeing to cover costs of the disruption, while the 737 MAX received some support when International Airlines Group (IAG) announced at the June 2019 Paris Air Show it could order 200 jets. Opinion polls suggested most passengers are reluctant to fly again aboard the 737 MAX when it will be reintroduced, while most should be comfortable boarding it again after some time passes to prove its safe operations.

Financial and economic effects

The Boeing 737 MAX groundings 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 grounding. Boeing slowed MAX production to 42 aircraft per month until in January 2020, when they halted until the airplane is reapproved by regulators. Boeing has suffered directly through increased costs, loss of sales and revenue, loss of reputation, victims litigation, client compensation, decreased credit rating and lowered 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 global coronavirus pandemic and the resulting travel bans created further uncertainty and complications for Boeing. In March 2020, news that Boeing was seeking a $60 billion bailout caused a steep drop in its stock price. 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. Its customers, the airlines and aircraft lessors, had their operations and strategic plans severely disrupted.

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.[68]
  • Boeing 787 Dreamliner battery fires: the aircraft was grounded in 2013 for modifications to mitigate or contain risk of inflight fire.

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