NEW YORK (Reuters) – US inspectors have been considering grounding part of the Boeing 737 MAX aircraft last year after learning that the aircraft manufacturer has turned off the warning signal to warn of malfunctions in the MCAS anti-stall system. AFP a source close to the file.
C are employees of the Federal Agency of Aviation (FAA) were responsible for supervising and monitoring the airline Southwest Airlines, the largest customer of the 737 MAX, with a fleet of 34 aircraft in service at the time.
They had speculated that the aircraft could be immobilized to allow time to determine whether the pilots needed additional training or not, said the source on condition of anonymity.
After discussions, they had finally abandoned this track, but the information was not up to the top officials of the federal agency, said this source, confirming information from the Wall Street Journal.
The inspectors had discovered that Boeing had chosen to make the warning signal optional and paid after Southwest had asked the builder to reactivate it following the crash of a Lion Air 737 MAX 8 that resulted in the death of 189 people last October 29 in Indonesia.
Boeing had automatically disabled this signal in the 737 MAX delivered to Southwest without informing the airline. Neither it nor its pilots were aware of the changes when they began to fly the plane in 2017, told AFP a Southwest spokeswoman.
Like the regulators, they only became aware after the drama of Lion Air.
“Prior to the Lion Air accident, the signals (…) were presented by Boeing as operational, regardless of whether or not you selected the feature,” the Southwest spokesperson said.
But “after the Lion Air accident, Boeing informed Southwest that the signals were inoperable if we had not taken the option,” she added.
That’s when Southwest chose this option for all its devices, the spokeswoman said.
Contacted by AFP, Boeing ensured that the warning signal would now become a basic and free feature for all customers.
“This change will be made on all MAX whether they are in production or being modified for those who were on duty,” said a spokesperson.
The FAA did not want to comment on the immobilization information, but a spokesman said the signal was “an option for the airlines”.
MCAS was also implicated in the crash of an Ethiopian Airlines 737 MAX 8 that crashed on March 10, southeast of Addis Ababa, killing 157 people.
This air disaster resulted in ground immobilization across the planet of the 737 MAX fleet. Boeing is working on MCAS modifications to get the ban lifted, but the crisis, he said Wednesday, has already cost him $ 1 billion.
The bill is expected to rise, as the aircraft manufacturer will undoubtedly compensate airlines that have canceled thousands of flights until this summer and have had to expand their customer services and reservations teams.
The 737 MAX Ethiopian Airlines and Lion Air were not equipped with the warning signal, had revealed to AFP in March an industrial source.
Dubbed “disagree light” in the language of Boeing, this warning light would be triggered in the event of erroneous information transmitted by one or two angle of attack (AOA) probes to the MCAS stabilization system.
The latter measures the angle of attack and dive the aircraft to allow it to regain speed and move away from the risk of fatal stall.
According to initial evidence from Lion Air, one of the two AOA impact probes failed.
Another problem appeared during this same accident: although faulty, the probe continued to transmit information to the computers, in particular to the MCAS.
However, this instrument takes control of the flight controls and makes the aircraft dive, even if the pilot tries to do the opposite, as long as the system is not disabled.
With the AOA out of service, the MCAS should have been disabled. What did not know the crew of Lion Air.
Boeing suspended deliveries of 737 MAX and reduced production by about 20%.