Signage is displayed on the landing gear of a Boeing Co. 737 Max 9 jetliner at the company’s manufacturing facility in Renton, Washington, U.S. (Photographer: David Ryder/Bloomberg)

Boeing's 737 Max Crisis -- Your Questions Answered: QuickTake

(Bloomberg) -- First flown in 1967, Boeing Co.’s 737 has become the world’s best-selling commercial aircraft. The fourth generation of jets, known as the Max, made its debut in 2017 when Indonesian low-cost carrier Lion Air became the first commercial operator. Yet two fatal crashes within five months -- Lion Air Flight 610 in October off the coast of Indonesia and Ethiopian Airlines Flight 302 in March outside Addis Ababa -- have led to a global grounding of the aircraft and put the 737’s previously sound safety record under the microscope. The crashes have also raised questions about how U.S. flight regulators came to certify the Max.

1. Are the two crashes linked?

It’s too early to say. A preliminary study of the Ethiopian Airlines flight data recorders show “clear similarities,” according to Ethiopia’s transport minister. There were enough parallels for the U.S. Federal Aviation Authority -- the agency that originally certified the 737 Max -- to earlier reverse its initial recommendation not to ground the aircraft. The Lion Air Max 8 that crashed was 2 1/2 months old, the Ethiopian Airlines jet just four months old. In both crashes, the accidents took place not long after takeoff as the planes flew erratically and pilots asked to return to the airport. The investigation into the Oct. 29 Lion Air crash pointed to a malfunction of a safety feature, the Maneuvering Characteristics Augmentation System, that repeatedly forced the plane into a nosedive.

2. What is MCAS?

It’s a set of sensors and software that Boeing installed in the 737 Max to help pilots respond to a situation in which the wings are losing lift because the plane is climbing too steeply. Insufficient lift can produce an aerodynamic stall, which can cause a plane to plummet. If a so-called angle-of-attack sensor on the outside of the aircraft reports that its nose is aimed too high, MCAS is programmed to automatically lower it, allowing the plane to regain speed and lift. In the Lion Air crash, the system was activated by a reading from a single faulty sensor that had been improperly repaired after incidents on earlier flights. The pilots were baffled when the tool meant to stabilize the plane pushed the nose down multiple times, exerting more and more force until they lost control. All 189 people aboard died when it plunged into the Java Sea. Boeing says there is a simple procedure for shutting off MCAS in such situations, but the Lion Air pilots apparently didn’t follow it.

3. What do people say about the system?

The Dallas Morning News reported that pilots in the U.S. repeatedly voiced safety concerns about the Max 8 autopilot system to authorities months before the March 10 Ethiopian Air crash. Many veteran 737 pilots first learned of the flight-control changes on the Max in the aftermath of the Lion Air crash, and some were furious with Boeing for omitting any description of them from most flight manuals. Subsequently, the FAA and other regulators took steps to notify pilots of the MCAS and to remind them how to overcome it in the event of a malfunction. Boeing issued further guidelines on how to override the plane’s automated systems. The FAA says a more formal fix to redesign MCAS won’t be mandated until April. One report said it may come sooner.

4. Why is the FAA under scrutiny?

The U.S. Department of Transportation inspector general’s office was investigating the FAA’s approval of the Max before the second crash took place, Bloomberg reported, citing a person familiar with the probe. The office is seeking to determine whether the agency used appropriate design standards and engineering analysis to certify the anti-stall system, the Wall Street Journal reported earlier. The Seattle Times reported that FAA managers pushed engineers to delegate key parts of safety assessment to Boeing and to speed up approval of the resulting analysis, as development of the model was nine months behind that of rival Airbus SE’s A320neo. The safety report Boeing delivered to the FAA for the MCAS had several flaws, the report said. Boeing said there are “some significant mischaracterizations” in the engineers’ comments. FAA employees warned as early as seven years ago that Boeing had too much sway over safety approvals of new aircraft, prompting an investigation by transport department auditors who confirmed the agency hadn’t done enough to “hold Boeing accountable,” Bloomberg News reported.

5. How many airlines have purchased the 737 Max?

Plenty, but most orders have yet to be fulfilled. As of February, Boeing reported 376 deliveries of the single-aisle jets to 47 airlines or leasing companies. In total, orders from more than 80 operators exceed 5,000. Most sales are the Max 8, the model involved in both crashes. (There’s also, from smallest to biggest, a Max 7, 9 and 10.) The main operators include Southwest Airlines (31 in the fleet through February), American Airlines (24) and Air Canada (23). Norwegian Air, FlyDubai and several Chinese carriers also operate them. (Chinese airlines account for about 20 percent of 737 Max deliveries globally.) Click here for the full list.

Boeing's 737 Max Crisis -- Your Questions Answered: QuickTake

6. How disruptive have the groundings been?

With fewer than 400 Max jets in service, not very, at least for most airlines. In the U.S., for example, the Max makes up about 3 percent of the mainline fleets for three carriers: American, Southwest and United. Some impact will be felt in Miami, where American has concentrated its initial Max deliveries for service to the Caribbean and to New York’s LaGuardia airport. Passengers should be able to tell from their tickets or by checking websites such as flightstats.com whether their flight was supposed to be on a 737 Max. There may be a bump in ticket prices during peak season.

Boeing's 737 Max Crisis -- Your Questions Answered: QuickTake

7. How is the Max different from earlier 737s?

It has bigger engines, incorporates more automation, has a higher range (up to about 3,550 miles, or 6,570 kilometers) and uses less fuel. Visually, the 737 Max differs from older models through its distinctive double winglets and serrated engine housing. Some reviews complained about the new design squeezing in smaller bathrooms and more seats.

8. Were the airlines involved in the crashes safe?

While Africa has a generally poor aviation safety record compared with global norms, Ethiopian Airlines is known for operating a modern fleet that features Boeing 787 Dreamliners and the latest Airbus SE A350, as well as the 737 Max. The state-owned airline, Africa’s only consistently profitable carrier, has built Addis Ababa into a major hub feeding travelers from around the world into dozens of African cities in competition with rivals such as Dubai-based Emirates. Captain Yared Getachew had amassed more than 8,000 flight hours, according to the airline, while first officer Ahmed Nur Mohammod had spent about 200 hours aloft. The plane that crashed had flown about 1,200 hours. Indonesia’s aviation safety record has been criticized. Its airlines, including Lion Air, were banned from flying to the European Union and the U.S. for almost a decade until 2016 because of safety concerns.

Boeing's 737 Max Crisis -- Your Questions Answered: QuickTake

9. What does this mean for Boeing?

The 737 is the company’s largest seller and accounts for almost one-third of operating profit. There’ll be claims from airlines; Norwegian Air said it will seek compensation for the grounding of about 1 percent of its seats. And it may impact sales; Lion Air and several other carriers have suspended deliveries or put orders on hold. There’s also the prospect of substantial payouts to the families of passengers if Boeing is found responsible for the crashes. In the week after the second crash, Boeing lost more than $22 billion, or 12 percent, of its market value. Boeing issued a statement after the U.S. regulator grounded the aircraft saying it still has “full confidence” in the plane. According to an analysis of 47 commercial aircraft by Quartz, no model has been implicated in as many fatalities as quickly as the Max 8 since 1966.

The Reference Shelf

  • A QuickTake on MCAS.
  • Empty coffins buried: BBC.
  • Boeing’s reputation on the line.
  • This graphic identifies 737 Max customers.
  • A New York Times in-depth examination of the Lion Air crash.
  • Ethiopian Airlines’ 157 casualties include UN officials and academics.
  • A QuickTake on U.S. lawsuits from the Lion Air crash.
  • Flawed analysis, failed oversight: The Seattle Times.
  • Boeing’s 737 Max page.
  • China gets tough on the 737 Max.

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©2019 Bloomberg L.P.