Boeing 737 Max crashes show similarities, investigators find – CNET

After two deadly crashes of its 737 Max 8, Boeing is facing massive scrutiny over one of its newest and most critical aircraft models. The airliner remains grounded around the world, and Congress, the FBI and the Trump administration are calling for an inquiry into the FAA's certification process.

The developments are a huge blow to Boeing, which has thousands of 737 Max orders on its books. The official causes of the crashes, which appear to be similar, are still under study. But so far, investigation teams in Indonesia and Ethiopia are focusing on a flight control system designed to stop the aircraft from stalling. Until the official reports are published, here's what we know:

What happened in the most recent crash?

On March 10, Ethiopian Airlines flight 302 departed Addis Ababa Bole International Airport bound for Nairobi, Kenya. Just after takeoff, the pilot radioed a distress call and was given immediate clearance to return and land. But before the crew could make it back, the aircraft crashed 40 miles from the airport at 8:44 a.m., six minutes after it left the runway. Aboard were 149 passengers and eight crew members representing more than 30 nationalities.

The aircraft involved was only four months old. Africa's largest airline, Ethiopian serves cities worldwide (including the US) and is a member of Star Alliance, which includes United Airlines, Lufthansa and Air China. And despite Sunday's crash, and contrary to what some television presenters might think, Ethiopian has a strong safety record. The airline's last fatal crash happened in 2010.

What was the previous crash?

On Oct. 29, Lion Air flight 610 crashed in the Java Sea 13 minutes after takeoff from Jakarta, Indonesia, killing 189 people. As with the Ethiopian crash, the flight crew lost control early in its flight and made a distress call. That aircraft was almost brand-new as well, having arrived at Lion Air three months earlier.

What is the Boeing 737 Max 8?

One of Boeing's newest airliners, the 737 Max 8 made its first flight on Jan. 29, 2016, and entered passenger service with Malaysia's Malindo Air on May 22, 2017. Seating between 162 and 210 passengers, depending on the configuration, it's popular on shorter routes, but also has the range (3,850 nautical miles) to fly transatlantic and between the mainland US and Hawaii.

The design of the Max 8 is based on the Boeing 737, an aircraft series that has been in service since 1968. As a whole, the 737 family is the best-selling airliner in history. At any given time, thousands of some version of it are airborne around the world and some airlines, like Southwest and Ryanair, have all-737 fleets.

What's different about the Max 8?

Compared with previous 737 versions, the Max 8 has bigger, more powerful and more efficient CFM LEAP engines (more on those in a minute), improved aerodynamics and a redesigned cabin interior. It also can fly farther and carry more people than the previous generation of 737s, like the 737-800 and 737-900.

The 737 Max series consists of four models, of which the Max 8 is the most popular. The larger Max 9 has been flying only for a few months and the 737-10 is still in development and has yet to fly. A few airlines have ordered the smaller 737 Max 7, but Boeing has yet to complete any deliveries. (It flew for the first time last May.)

What caused the crashes?

The complete reports haven't been published yet. Crash investigations are tremendously complex — it takes months to evaluate the evidence and determine a probable cause. Investigators must examine the debris, study the flight recorders and, if possible, check the victims' bodies to determine the cause of death. They also involve multiple parties including the airline, the airplane and engine manufacturers and government agencies.

There are important clues so far. Remember those larger CFM LEAP engines? Well, because they're bigger, and because the 737 sits so low to the ground (a deliberate design choice to let it serve small airports with limited ground equipment), Boeing moved the engines slightly forward and raised them higher on their underwing pylons. (If you place an engine too close to the ground, it can suck in debris while the plane is taxiing.) That change allowed Boeing to accommodate the engines without completely redesigning the 737 fuselage.

But the new position changed how the aircraft handled in the air, creating the potential for the nose to pitch up during flight. A pitched nose is a problem in flight — raise it too high and an aircraft can stall. To overcome this action, Boeing designed software called the Maneuvering Characteristics Augmentation System, or MCAS. When a sensor on the fuselage detects that the nose is too high, MCAS automatically pushes the nose down.

Investigators in the Lion Air crash have said that a fault in the the sensor may have been feeding incorrect data to MCAS, pitching the nose down into a dive. According to the preliminary report (PDF) from the Indonesian National Transportation Safety Committee, the Lion Air pilots were unable to determine their true airspeed and altitude and they struggled to take control of the plane before the crash, as it oscillated for 10 minutes. Each time they pulled up from a dive, the system pushed the nose down again. (For a thorough explanation of MCAS, see this story from The Air Current.)

The report also noted that maintenance crews had replaced the faulty sensor two days before the flight and that pilots on the four flights preceding the crash reported incorrect airspeed and altitude information (a passenger likened one of those flights to a "roller coaster ride").

The Air Current and The New York Times reported that the Lion Air plane also lacked a warning light designed to alert pilots to the fault and that Boeing sold the light as part of an optional package of equipment. When asked about the warning light, a Boeing spokesman gave CNET the following statement:

"All Boeing airplanes are certified and delivered to the highest levels of safety consistent with industry standards. Airplanes are delivered with a baseline configuration, which includes a standard set of flight deck displays and alerts, crew procedures and training materials that meet industry safety norms and most customer requirements. Customers may choose additional options, such as alerts and indications, to customize their airplanes to support their individual operations or requirements."

Are the two crashes related?

So far, it appears that they are. Investigators in France are still examining the flight recorder (the "black box") from the second crash, but Ethiopia's Transport Minister said on March 18 that two crashes have "clear similarities." Though he didn't elaborate, satellite data released March 14 showed that the final flight track of the Ethiopian Airlines jet was similar to that of the Lion Air plane. The FAA cited that data in its grounding order.

Investigators at both crash sites have also recovered the jack screws, which manipulate the control surfaces on the horizontal stabilizer that pitch the nose up and down. Both jack screws were set to send the planes into a dive.

Do we know anything else about the Ethiopian crash?

According to the preliminary report released on April 4, the flight crew initially followed Boeing's emergency procedures to disable MCAS by cutting electrical power. For unknown reasons, though, they later turned the system back on as many as four times after they were unable to regain control under manual power.

Initial findings also suggest that the aircraft's fuselage sensor was damaged. Like with the Lion Air crash, the sensor may have then been feeding erroneous data to the MCAS system.

In a statement issued the same day, Boeing Commercial Airplanes President and CEO Kevin McAllister thanked Ethiopia's Accident Investigation Bureau for its hard work. "Understanding the circumstances that contributed to this accident is critical to ensuring safe flight," he said. "We will carefully review the AIB's preliminary report, and will take any and all additional steps necessary to enhance the safety of our aircraft."

What's the current status of the Max 8?

Most operators quickly grounded their planes in the days following the second crash. That list includes both Ethiopian Airlines and Lion Air, but also AeroMexico, Aerolíneas Argentinas, GOL Linhas Aéreas (Brazil), Turkish Airlines, S7 Airlines (Russia), FlyDubai, Air Italy, Cayman Airways, Norwegian, China Eastern Airlines, Fiji Airways and Royal Air Maroc.

More than 40 countries have also banned the 737 Max from flying in their airspace. China (a huge Boeing customer and a fast-growing commercial aviation market) led the way and was joined by Indonesia, Thailand, Malaysia, Australia, India, Oman, the European Union and Singapore, Canada initially hesitated, but soon reversed course.

Up until March 13, the FAA also declined to join the grounding order, saying in a statement tweeted the previous day that there is "no basis to order grounding the aircraft." That was despite a public outcry from a group of senators and two flight attendant unions. But along with Trump's order, the agency said it issued the order due to new evidence it collected and analyzed (see below). The grounding will remain in effect pending further investigation.

Southwest and American have pulled their 737 Max 8s from service and have adjust their schedules to make up for the lost aircraft. The only other holdout, Panama's Copa Airlines, has grounded its planes, as well. The order also has grounded the 737 Max 9, currently in service with United Airlines.

Older 737 models, like the 737-700, 737-800 and 737-900 don't use the flight control system under investigation and aren't affected.

How has Boeing responded?

On Nov. 6, Boeing issued a safety warning advising 737 Max operators of the potential for a sensor failure and instructing them how to deactivate MCAS by flipping a switch. But two days later, The Seattle Times reported that Max 8 pilots were not specifically trained on using MCAS. The reason? According to The New York Times, it was because Boeing, backed by the FAA, wanted to minimize the cost and time of certifying pilots who had already been trained on other 737 versions. An investigation by The Dallas Morning News found that several Max 8 pilots had complained about the inadequate training.

Following the second crash, the company expressed sympathy for the victims' families and said it was sending an investigation team. Then on March 12, Boeing said it was continuing to work with Max 8 customers that have grounded their aircraft.

"Safety is Boeing's No. 1 priority and we have full confidence in the safety of the 737 Max," the statement said. "The United States Federal Aviation Administration is not mandating any further action at this time, and based on the information currently available, we do not have any basis to issue new guidance to operators."

Now playing: Watch this: How United Airlines prepares a Boeing 777 between flights

2:33

On March 13, however, in response to the US grounding order, the company said it supports the action.

"There is no greater priority for our company and our industry," the statement said. "We are doing everything we can to understand the cause of the accidents in partnership with the investigators, deploy safety enhancements and help ensure this does not happen again."

As is common after a crash, Boeing has not commented on specific aspects of the investigation, but on March 11, the company said it would issue a software update by the end of April that would include changes to MCAS, pilot displays, operation manuals and crew training (for more details on those changes, see link above).

But even that timeline is question. The Wall Street Journal reported on March 12 that a MCAS update could have come in January before the second crash. The newspaper says it was delayed, however, by the 35-day US government shutdown earlier this year.

Dennis Muilenburg, Boeing's chairman, president and CEO also published a letter April 4 expressing confidence in the fundamental safety of the 737 MAX. "All who fly on it — the passengers, flight attendants and pilots, including our own families and friends — deserve our best," he wrote. "When the MAX returns to the skies with the software changes to the MCAS function, it will be among the safest airplanes ever to fly."

What does this mean for the FAA?

The agency is under fire on multiple fronts over the crashes. Congress, the Read More – Source

[contf]
[contfnew]

cnet

[contfnewc]
[contfnewc]