Boeing 737 Max: answers to questions from around the world

The Boeing 737 Max has been immobilized worldwide since March 2019 following two fatal accidents involving the aircraft's anti-stall system.

Ten weeks after the latest accident, security authorities around the world are gathering in Fort Worth, Texas, to inform the aircraft manufacturer what steps it has taken to prevent further tragedies. Representatives from 33 countries will also be questioning the US regulator, the Federal Aviation Administration, about its role in aircraft certification.

These are key questions.

What is the importance of the Boeing 737?

This is the plane that, more than any other, has helped to democratize aviation. The 737 is the most popular airliner in the world in terms of the number of sales. Over the last fifty years, more than 10,000 vehicles have been built, putting it well ahead of its main competitor, the Airbus A320.

The jet is spearheading many airlines – including Ryanair, which operates exclusively on the 737-800, and America's largest low-cost carrier, Southwest.

How is the Max version different?

Boeing had to offer airlines a more efficient jet. The company could have designed a new aircraft, but instead chose to continue the evolution of the 737. One of the commercial strengths of this approach is the commonality: the idea that trained pilots to the generation current aircraft can be transferred to the Max with a minimum of training.

The last variant, which started flying in service scheduled two years ago, uses much of the same cell, but its engines are much bigger – a development that improves the aircraft's energy efficiency. .

The Boeing 737 is much lower on the ground than its more modern counterpart, the Airbus A320. This feature allows pbadengers to get on and off the plane using its own internal steps and facilitates the access of the engineers.

But this also challenged Boeing's designers. If the last big engines had simply been suspended on the wings, as in the previous versions, the ground clearance would have been insufficient.

The problem has been solved by mounting the engines higher, so they are integrated in the wing and significantly more forward. This change, however, has aeronautical consequences. Under certain circumstances, the aircraft may tip up, increasing the risk of stall, as the wings do not generate enough lift so that the aircraft can continue to fly safely.

How was this problem addressed?

With a new software called Manicure Enhancement System (MCAS). The anti-stall system monitors the angle between the wing and the airflow, called the "angle of attack". This is measured by a wind vane on the outside of the plane. If the system detects that the angle becomes dangerously stiff, it activates an elevator in the tail to push the nose down – and this, repeatedly, even canceling the pilot's commands.

On October 29, 2018, a Boeing 737 Max operating under flight number 610 from Lion Air took off from Jakarta. Only one defective angle of attack sensor triggered the MCAS response. He initiated a fatal fight between the pilots and the anti-stall system. As the captain and the first officer struggled with the controls, MCAS repeatedly lowered the nose of the plane, causing an accident that killed all 189 pbadengers and crew members.

What happened after this tragedy?

Boeing provided advice to 737 operators and Max pilots on how to combat a misplaced MCAS. But on March 10, 2019, flight 302 of Ethiopian Airlines crashed at high speed shortly after takeoff from Addis Ababa, causing the death of 157 pbadengers and the crew.

The initial investigation showed that the pilots were fully aware of the problem and had responded appropriately. But the badpit voice recorder and the black box investigators revealed another battle between two men and technology installed on one of the most modern aircraft in the world.

While the cause of the accident was better known, aviation authorities around the world began to anchor the Boeing 737 Max. Although the highly respected British Civil Aviation Authority (CAA) banned the aircraft from leaving British airspace, the FAA insisted that there were no fundamental problems.

About 24 hours later, the FAA also issued a grounding order.

What security authorities want to know?

They want answers to a series of specific questions about Boeing engineers' improvements to anti-stall software. procedural changes; and what training the planner proposes to offer to ensure that flight crews around the world are aware of the new system and its limitations.

But they will also ask research questions about the initial certification of the Boeing 737 Max. Repeated accusations that the manufacturer and the FAA have become too close, as the safety regulator failed to challenge the designers.

In the process, the principle of redundancy, which allows multiple breakdowns without jeopardizing the plane, seems to have been neglected. For an airplane to crash after events triggered by a single failure – in this case, the angle sensor attack – goes against from the philosophy of aviation safety.

In previous strandings, including the Boeing 787 Dreamliner in 2013, the world has just taken the lead in the FAA. This may not happen again.

What is the effect of the grounding?

Summer is the busiest aviation in the world, and the inability to fly more than 500 aircraft has been a big problem for many airlines, including American Airlines, Norwegian, Tui and Ryanair – which was to begin to fly a Boeing 737 Max specially designed for this purpose. the -200 version this month.

Additional capacity is reserved to respect schedules, but some flights are canceled. The cost to the airlines is in the billions of pounds. This month, Tui said that the costs badociated with chartering aircraft and other measures to address the grounding would go to 200 million euros. – if the plane was allowed to fly in time for the record month of August – to 300 million euros if the grounding continued until the scheduled time . end of summer.

At the meeting in Fort Worth, it will be known that the FAA has no timetable for the return to service of the Boeing 737 Max. Interim administrator, Dan Elwell, said: "It takes a year to find everything we need to give us confidence to lift the order, while there is so."

What did it do to trust Boeing?

The whole sad saga has proved extremely detrimental to the builder's reputation with airlines, pilots and pbadengers. The grounding of the Boeing 787 Dreamliner, which lasted four months, was imposed after a series of battery fires, none of which harmed the traveling public. There is now praise for this plane.

But the defects of the 737 Max are involved in two calamitous tragedies. Even when the grounding order is lifted, the concern will probably persist.