Lawmakers Seek Documents on Boeing’s Faulty Sensor Alert

House lawmakers demanded records from Boeing Co., one of its suppliers and U.S. aviation regulators on why a cockpit alert that might have helped pilots in two recent fatal 737 Max crashes was installed with a defect that made it inoperable.

Representative Peter DeFazio, the Oregon Democrat who heads the House Transportation and Infrastructure Committee, on Friday sent letters to Boeing, United Technologies Corp. and the Federal Aviation Administration requesting a timeline and other documents related to the alerting system.

Boeing had installed an indicator light on a cockpit display that was supposed to illuminate when weather-vane-like sensors on the nose of the 737 were malfunctioning, but software issues prevented it from working in some configurations. Airlines operating the new plane weren’t told about the faulty alert until after the accidents, even though Boeing knew about the issue in 2017. Failures of that sensor, known as angle-of-attack, were what led the planes to automatically try to dive in both deadly crashes.

“The fact that Boeing knew about a defect for more than a year before disclosing it to the FAA is of great concern to me,” DeFazio said in a press release.

DeFazio was joined by Representative Rick Larsen, a Washington Democrat who is chairman of the aviation subcommittee, in making the request. It was the second call for records in the committee’s investigation of the two crashes on the 737 Max that have claimed the lives of 346 people and resulted in the grounding of Boeing’s best-selling jet.

Software for the cockpit alert on the angle-of-attack sensor is made by Rockwell Collins Inc., which was acquired by United Technologies. Another United Technologies division makes the angle-of-attack vanes for the plane.

FAA Acting Administrator Daniel Elwell told House lawmakers at a May hearing that regulators didn’t believe the defective alert was a safety-critical item because pilots had other ways to detect a failure, but the agency was concerned the manufacturer hadn’t disclosed it.

Boeing’s internal experts reviewed the issue after it was discovered and determined the flaw wouldn’t affect safety and they planned to fix it during the next software update for the plane, the company said in May.

The cockpit alert only worked on airplanes that displayed the position of angle-of-attack sensors. Most airlines opted not to purchase the extra display, rendering it unworkable on most of the delivered 737 Max aircraft.

It’s not clear whether having a working cockpit alert would have made a difference in either the October crash of a Lion Air jet off the coast of Indonesia or the March accident near Addis Ababa, Ethiopia. In the Ethiopia Airlines crash, for example, pilots recognized the type of failure they faced, but still couldn’t control the plane, according to a preliminary investigative report.