The reasons behind the tragedies of the Boeing 737 MAX

In 2010, the European consortium Airbus presented the A320neo aircraft, a development of an existing platform, and developed aeronautics.

With refined aerodynamics and modifications to the cab and engines, thethe aircraft achieved a fuel economy of 15% at a time when airlines are trying to reduce their costs by any means possible.

He flew for the first time in 2014 and entered service with Lufthansa in 2016, quickly becoming a commercial success with 6,501 orders, in its A319, A320 and A321 versions, and 678 aircraft delivered.

Boeing, mythical American builder and only real competitor of Airbus in the global duopoly of commercial aircraft, began to lose market. The competitor of the A320neo was its 737 Next Generation, a high-performance and reliable aircraft that, however, was behind in fuel consumption.

The competition led to the launch in 2011 of the 737 MAX, the fourth version of the aircraft designed in the 1960s, with new engines and a series of modifications aimed at leveling the situation with the A320neo. It flew for the first time in 2016 and entered service in 2017, after receiving 5,011 orders and delivered 350 aircraft.

The MCAS system and two similar accidents

Although data is still expected on black boxes in Ethiopia, it has been reported that the accident in Indonesia occurred in October this was due to a failure of the altitude and speed sensors, a resulting conflict with the automated MCAS system and the inability of the crew to disable the latter.

Accidents share similarities. ABoth aircraft fell shortly after takeoff, both pilots They reported a problem and asked to return to the airport, and both flights were detected similar patterns of vertical speed changes, ie steep climbs and descents.

Investigations into what happened in the tragedy of Indonesia indicate that the erroneous information generated by a sensor failure, already detected in previous flights, led the MCAS to make erroneous corrections to the aircraft's stabilizers, causing the fall. The same thing could have happened in Ethiopia.

MCAS (System for increasing maneuvering characteristics or system to increase maneuvering characteristics) so remained at the center of attention, especially because, according to a complaint by the Union of American Pilots (ALPA), its existence and the cancellation procedure would not have been included by Boeing in the manuals (FCOM), at least before the accident in Indonesia.

Look on automation

The MCAS function consists of correcting the inclination of the nose of the airplane, or its angle of attack, in order to avoid the so-called "stall", the moment the plane reaches a speed below the minimum and loses lift, then falls as if it 's been a stone. In this way, when the instruments signal that the device goes up too much, it loses speed quickly, the MCAS intervenes and corrects automatically.

If the information is wrong, the correction will cause the crash of the aircraft on the ground. That's why it's possible to cancel the system, but it's not a simple procedure and the crews were not initially trained to do so simply because they did not appear in the FCOM.

The reasons for this alleged clipping vary. According to statements by Southwest Airlines, the main user of the Boeing 737 MAX in the United States, collected by the specialized newspaper The air stream, Boeing decided not to include information on the MCAS because "since it works in situations of very high gravitational load and close to stall, a pilot must not see the operation of the MCAS".

"The pilot probably does not realize it," says the Southwest text. The explanation dispelled no doubt, but she was the only officer present after the accident in Indonesia.

Almost at the same time, experts related to the investigation into this tragedy told the Wall Street Journal that Boeing's motivation to not give details about his new system had to do with "Do not flood the average drivers with too much information, especially technical data, which they need or can digest."

This mountain of technical data on the operation of MCAS was finally sent by Boeing to its customers, but only after the death of 189 people on the Lion Air flight. But that's not the end, as the Sunday crash showed.

The problem of the weight of the engines

The development of the MCAS may have another explanation, in addition to the desire to automate processes that has been a trend of the aviation industry over the last few decades, as it is. pbaded with the "fly by wire" system (or flight with electronic controls).) introduced by Airbus in its first A320 and that caused problems and fatal accidents at the time.

Apparently, the new 737 MAX CFM International LEAP-1B engines, which offer similar fuel consumption levels to those of the A320neo, arebigger and heavier than those used in the 737 Next Generation.

As the 737 are notoriously low planes when they are on land, it stands out The current of air, the new engines had to be placed in a higher position and just a little ahead of the previous ones. This required the extension of the landing gear before.

Although it seems minorall these changes resulted in changes to the aircraft's mbad and aerodynamics, affecting the behavior of the 737, a platform known for its stability. The new MAX has turned out to have a tendency to raise the nose, generating the risk of stalling if it is not compensated adequately by the pilot. To counter this problem, MCAS has been developed, claiming that the system did it silently and effectively without even the pilot's noticing that the plane had a dangerous trend.

The process also checks a shadow on the procedures of the United States Federal Aviation Administration (FAA), who certified the safety of the aircraft in 2017, was lukewarm after the accident occurred in Indonesia in 2018 by issuing an emergency directive to revise the certificates and It took several days to ban the 737 MAX flights in 2019 after the tragedy in Ethiopia.

For many experts, the changes made to the 737 MAX were so important and had an impact on the behavior of the aircraft.that they must demand a total certification of the aircraft as it was completely new, a long and expensive processas indicated by a site survey NCC based on the opinions of NASA engineers.

Boeing, for its part, agreed with the FAA to partially certify the modifications and the new parts themselves, keep the general certificates issued for the 737 Next Generation, which steals in another way.