The crashes of Boeing 737 Max 8 from Lion Air in October and Ethiopian Airlines in March would have originated a failure of the anti-stall system of the aircraft. Boeing announced Friday, March 21 that equipment reporting this malfunction would no longer be optional.
An optional warning signal, pilots not trained enough, the flight certification procedure attributed to the device in question: a puzzle of malfunctions begins to assemble to try to understand the cause of the two Boeing 737 Max crashes causing the death of 346 people.
The fate of the aircraft darkened on Friday (March 21st), when Garuda, the Indonesian national airline, announced the cancellation of an order for 49 aircraft, saying that its customers had lost confidence in this model. At the same time, Ralph Nader, an American lawyer famous for his campaigns for consumer rights since the 1960s, called for the creation of an advocacy organization for passengers. These announcements follow the discovery of the origins of the crash of 29 October, off the island of Java in Indonesia, and that of 10 March, north-east of Addis Ababa, the capital of the Ethiopia.
Crash in Ethiopia, a wind of desolation
Very quickly, the Ethiopian investigators and their French counterparts, dispatched to assist in the analysis of the flight recorders, pointed out the role of a new equipment designed to prevent the aircraft from flying out manually, the MCAS ( an acronym that could be translated as "system for improving maneuverability characteristics"), and referred to "Clear similarities" between the two disasters.
The anti-stall system at the center of attention
With this system, one or two probes measure the incidence of the aircraft, also known as the angle of attack. When this angle of attack is excessive, the aircraft risks stalling and loss of control. Before reaching this stage, the MCAS intervenes and puts the aircraft in a dive to allow it to regain speed.
During both crashes, the MCAS received erroneous information, one of the two sensors measuring the angle of attack being defective. Boeing had made the light signal warning of a malfunction of the anti-stall system a pay option. Neither Lion Air nor Ethiopian Airlines, victims of the crashes, had taken it, unlike American companies.
In addition, the crew of Lion Air was not able to disable the MCAS: Boeing would have underestimated the need for crew training software that he equipped all 737 Max. "An anti-stall system, by itself, is great, says Claude Carlier, aeronautics specialist. But perhaps, both in terms of Boeing and companies, we underestimated the need to teach crews the handling of this new tool. Many programs have difficulties in their infancy, this was also the case of the Airbus A320, the competitor of the Boeing 737. It is still a bit early to draw definitive conclusions. "
SLIDESHOW – Ethiopian Airlines Boeing crash, time of mourning
The certification procedure in question
The US Department of Transportation has commissioned an audit on the certification issued to the 737 Max by the US Federal Aviation Administration (FAA). It appeared that the latter, deemed close to Boeing and faced with a lack of resources, had delegated its certification work to employees of the aircraft manufacturer. Which, according to a former FAA official, Michael J. Dreikorn, returns to "Entrust the fox to keep the hen house", and motivates Ralph Nader's initiative to create a victims' association.
Boeing has already ensured that the warning signal, hitherto optional, would now systematically equip all 737 Max, nailed to the ground since the second disaster. The blow is tough for the American manufacturer, who has delivered only 370 out of the 5,000 ordered aircraft: the program is vital for the aircraft manufacturer, which ensures that the pace of production will be maintained, while conceding improvements from the week next, officially due to winter storms that have lengthened the delivery times of its suppliers.