Southwest Airlines says Boeing did not disclose that certain safety features on the troubled 737 Max aircraft were not “operable”, raising further questions about poor communication between the manufacturer and its customers ahead of its shareholder meeting on Monday.
Southwest, the largest global carrier with 737 Max aircraft in its fleet, told the Financial Times that it believed it had functioning alerts installed on its Max aircraft so that its pilots would be made aware when the jet’s two angle of attack (AOA) sensors disagreed, signalling a malfunction.
Preliminary crash reports indicate that such a malfunction in the sensors, which show the angle of the plane’s nose in relation to the ground, were a central feature in both the Ethiopian and the Indonesian crashes of the 737 Max aircraft which killed 346 people.
The 737 Max has been grounded worldwide since mid-March, affecting the financial results of carriers in the US and Europe which have had to shift passengers on to different aircraft.
After the crash of a Lion Air flight in October, Southwest says it was notified by Boeing that the so-called disagree alarm would not work unless the carrier also installed an optional display of AOA information in the cockpit, so Southwest chose at that point to add the additional option.
“In working with Boeing on Max deliveries, the AOA disagree lights were standard equipment on all Max aircraft,” Southwest said. “The only option we had was to upgrade to the AOA (display) indicators. Can only speak to conversations we had with Boeing.”
The Federal Aviation Administration, the US aviation regulator, told the Financial Times that the disagree alert was optional on the Max, and not standard.
The disagree alert will be standard in future on Max deliveries and existing Max aircraft will be retrofitted with it, Boeing has said. It will no longer require the AOA cockpit display, which will remain optional but carriers can choose it at no extra cost.
Industry sources said that before the two crashes, carriers needed to choose both options — the disagree alert and the cockpit display — together. They could not be ordered separately.
“A new software update will separate those two features, making AOA disagree alert a standalone standard feature and keeping AOA indicator as an additional customer-selected option,” Boeing said on Sunday.
Southwest Airlines’ pilots union says they were under the impression that the carrier had working disagree alerts on its Max aircraft because they were referred to in its manual.
“Post Lion Air, we were still under the impression disagree lights worked as that is what the Southwest manual said at the time. SWA’s own manuals were wrong. The company didn’t know either,” said Jon Weaks, union president.
Aviation experts said it was not clear why Southwest was unaware that it did not have functional disagree alerts in its aircraft. American Airlines, another big US Max carrier, had both safety options installed and its pilots union was reassured by Boeing after the Lion Air crash that they were working, American said.
Additional reporting by Kiran Stacey in Washington