American regulators considered grounding some Boeing 737 Max planes last year after learning of a fault with a system that is now the chief suspect in two deadly crashes, according to a source close to the matter.
Investigators in the Lion Air crash in October off the coast of Indonesia and the Ethiopia Airlines disaster in March have focused on the planes’ anti-stall system, called the Maneuvering Characteristics Augmentation System (MCAS).
Last year, inspectors with the Federal Aviation Administration discovered Boeing de-activated a signal designed to inform the cockpit crew of a malfunctioning of the MCAS system, the source said.
The inspectors were in charge of monitoring Southwest Airlines, the biggest user of 737 Max planes, with a fleet of 34 of them at the time, added the source.
Before the Lion Air crash, which killed all 189 people on board, “the [signals] were depicted as operable by Boeing on all Max aircraft” regardless of whether the cockpit crew thought they had them turned on or off, said a Southwest spokeswoman.
She said after the accident, Boeing told Southwest the signals were “turned off unless they were specifically designated as being turned on” – prompting the airline to choose that option for all its aircraft.
It was at that point inspectors learned Boeing had decided to make the malfunction alert an optional extra costing more money – and had deactivated the signal on all 737 Max delivered to Southwest without informing the carrier.
They considered recommending grounding the planes as they considered whether pilots flying the aircraft required additional training about the alerts, said the source.
They decided against that – but never passed details of the discussions to higher-ranking officials in the FAA, the source said, confirming a story in The Wall Street Journal.
The FAA would not comment on the planes coming close to being grounded last year.
The Ethiopia Airlines crash left all 157 people on the plane dead and led to all Boeing 737 Max planes all over the world being grounded. In this case, the MCAS is also being looked at as a possible cause of the crash.
In times of mid-air distress, the system is supposed to activate on its own and push the nose of the plane down to keep it from stalling.
Boeing is working on changing the MCAS so it can get the planes back in the air.
– with reporting by AFP