Boeing knew of 737 Max alert issue linked to crashes for a year before telling US regulator
Plane maker told FAA that feature was no longer available as standard only after Lion Air crash
Boeing did not tell US aviation regulators that a safety feature, available on earlier models as standard, had become an optional extra on its 737 Max aircraft.
The plane maker told the Federal Aviation Authority that the alert mechanism was no longer a standard fitting only after one of the aircraft, operated by Indonesian carrier Lion Air, crashed with all 189 people on board killed in October last year.
Five months later another 737 Max, operated by Ethiopian Airlines, also crashed, killing 157 people and leading to the model being grounded around the world.
Boeing said yesterday in a statement that the mechanism, called the Angle of Attack Disagree alert, was not a safety feature but provided supplemental information to the crew.
The alert warns of conflicting information from two sensors with regards to the plane’s nose in relation to the air stream.
The safety feature that displays discrepancies from the two sensors was available for a fee, so the AOA Disagree light worked only for airlines that bought it.
Accident investigators have linked erroneous data from AOA sensors to the two incidents.
The US plane maker did not reveal to the Federal Aviation Administration for more than a year, until after the Indonesia crash, that it had inadvertently made the alarm optional. It insisted the missing display did not represent a safety risk.
“Boeing discussed the status of the Angle of Attack Disagree alert with the FAA in the wake of the Lion Air accident,” the company said yesterday.
“At that time, Boeing informed the FAA that Boeing engineers had identified the software issue in 2017 and had determined per Boeing’s standard process that the issue did not adversely impact aircraft safety or operation.
“Neither the angle-of-attack indicator nor the AOA Disagree alert are necessary for the safe operation of the aircraft.
“They provide supplemental information only, and have never been considered safety features on commercial jet transport airplanes.”
The jet maker’s latest disclosure raises further questions about the extent of its transparency and certification process of the troubled 737 Max.
Boeing is facing the worst crisis in its history after the new single-aisle narrow-body model was involved in the two crashes.
Growing scrutiny and mounting lawsuits by families of the crash victims could pose a challenge to its efforts to revive confidence in the 737 Max and lift the global ban.
When the discrepancy was found, Boeing conducted a review, determined that the existing function was acceptable and decided to delink the alert and the indicator in the next planned update for the display system software.
Senior company leadership were first made aware of the issue after the Lion Air accident, Boeing said.
In December, it conducted another safety review, which confirmed the earlier conclusion that the alert was not necessary for safe operations of the aircraft, a result it shared with the FAA.
Boeing briefed the FAA on the display issue in November, after the Lion Air accident, and a special panel deemed it to be “low risk”, an FAA spokesman told Reuters.
“However, Boeing’s timely or earlier communication with the operators would have helped to reduce or eliminate possible confusion,” he said.
Flydubai, the UAE’s sole operator of the 737 Max, said it had no comment on Boeing’s disclosure.
When the jet returns to service, it will have the AOA Disagree alert as a standard feature, Boeing said.
Updated: May 6, 2019 10:37 PM