Boeing: the United States considered an independent review of the 737 MAX anti-stall system unnecessary


The 34 Boeing 737 MAX 8s fleet of the Southwest American airline has been grounded since mid-March (AFP / Mark RALSTON)

The US authorities did not consider it necessary to independently evaluate the safety of the 737 MAX MCAS anti-stall system, preferring to rely on Boeing's results on the software involved in two tragedies involving the aircraft, he said Tuesday. to AFP a source close to the file.

This information is part of the preliminary results of an internal audit by the Federal Aviation Agency (FAA) on the certification of the 737 MAX, whose inspection of part of the systems was entrusted to Boeing engineers via a procedure established about ten years ago called the ODA.

The Wall Street Journal says that during the 737 MAX certification, Boeing did not tell the authorities that the MCAS malfunction could be disastrous at the time of certification just over two years ago.

If the aircraft manufacturer had done so, this would have triggered an in-depth revision of the software, the malfunction is the cause of the crash of the Ethiopian Airlines 737 MAX 8 accident that killed 157 on 10 March, according to the preliminary survey.

It is also an MCAS problem that would have caused the tragedy of a 737 MAX 8 of Lion Air on 29 October in Indonesia, after completing 189 deaths.

These two dramas have led to the grounding of the entire 737 MAX fleet worldwide since mid-March.

– No test flights yet –

Uncertainties are hovering over a return to service of this aircraft, Boeing has not yet submitted to the US regulatory authorities the modification of the 737 MAX for the abolition of the flight ban and the test flight with the FAA has not yet taken place , a government source told AFP Tuesday.

On May 22, the FAA invited the civil aviation authorities of various countries in the United States to explain how it inspected the modified 737 MAX.

The FAA initially approved the 737 MAX at the beginning of 2017 and entered service in May of that year.

Maneuverability Features The Augmentation System (MCAS) is a system that optimizes the flight profile and maintains the aircraft in a safe trajectory.

It's new on the 737 MAX, a re-engineered version of the 737. To evolve this last, the American aircraft manufacturer has installed more powerful engines.

It was therefore necessary to protect the aircraft from a higher risk of stalling, hence the development of the MCAS.

The first elements of the Lion Air investigation revealed that one of the two AOA incidence probes had failed but had continued to transmit information to the ECUs, including the MCAS.

But this software takes control of flight controls and directs them even if the driver tries to do the opposite until the system is disabled.

– The companies assigned –

The FAA's internal audit indicates that Boeing did not intend to deceive the regulator, AFP told the source, adding that the FAA itself had already established that the MCAS was not influencing the flight path. unit.

The regulator also considered that no further control was needed because the changes made by Boeing did not affect the way the MCAS operated in flight, especially in the event of sudden or "problematic" movements, the same source said near the file .

The FAA also considered that, in the case of incorrect data sent to MCAS, the pilots had been trained to deactivate it and regain control of the aircraft.

"The MCAS did not trigger an additional safety assessment because it did not affect the most critical flight phase, considering cruising speed," an AFP spokesman told AFP. the FAA.

Contacted by AFP, Boeing, which announced an almost 25% drop in civil aircraft deliveries in the first four months of the year, did not respond.

The news comes on the eve of a hearing at the United States Congress by Daniel Elwell, the interim chief of the FAA.

In addition to the FAA, the Ministry of Transport is conducting an audit of the 737 MAX, while the Ministry of Justice is conducting a criminal investigation into the design of this aircraft from November.

American Airlines and Southwest, two large customers of the 737 MAX, received court summons in November to request information after the collapse of Lion Air, said two sources close to the case at the AFP on Tuesday.

"We are fully cooperating with the investigations," a Southwest spokeswoman said.

lo / alb / AB

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