Faulty 737 sensor in Lion Air crash linked to Florida repair station

Washington, DC

A FAULTY sensor on a Lion Air 737 Max that's been linked to the jetliner's deadly crash last October and a harrowing ride the previous day was repaired in a US aircraft maintenance facility before the tragedy, according to investigative documents.

Accident investigators in Indonesia, home of Lion Air, and the US, where Boeing Co, the plane's manufacturer, is based, have been examining the work that a Florida repair shop previously performed on the so-called angle-of-attack sensor, according to briefing documents prepared for Indonesia's Parliament.

Erroneous signals from that sensor triggered the repeated nose-down movements on the Oct 29 flight that pilots struggled with until the jet plunged into the Java Sea, killing all 189 people aboard, according to a preliminary accident report by Indonesian investigators.

The Lion Air crash and a similar one about five months later, involving an Ethiopian Airlines 737 Max together prompted the grounding of Boeing's bestselling jet on March 13 and touched off a global rebellion against US aviation regulators. Investigators have focused on the sensor's role in the two disasters.

Documents obtained by Bloomberg show the repair station XTRA Aerospace Inc in Miramar, Florida, had worked on the sensor. It was later installed on the Lion Air plane on Oct 28 in Bali, after pilots had reported problems with instruments displaying speed and altitude. There's no indication the Florida shop did maintenance on the Ethiopian jet's device.

The Indonesian National Transportation Safety Committee is seeking data "from a repair station in Florida" where the unit was worked on, the investigative agency said in a briefing to Parliament last November and contained in a presentation.

"Our thoughts and condolences are with all those who have lost loved ones in the recent 737 Max 8 accidents," XTRA Aerospace, a unit of Wencor Group LLC, said in a written statement. The company, it said, "is fully committed to supporting any investigations into this matter".

Nurcahyo Utomo, lead investigator at the Indonesia NTSC, said the US National Transportation Safety Board was conducting a review of the work performed on the sensor, but hasn't yet reported back on its findings.

The sensor was made by Rosemount Aerospace Inc, of Minnesota, a subsidiary of United Technologies Corp. United Technologies declined to comment, citing the investigation.

The sensor involved in the crash wasn't working from the time it was installed, according to the NTSC's preliminary report on the accident.

Angle-of-attack sensors, which operate like a wind vane on the side of a jet, are designed to show how air is flowing relative to where the nose is pointed, and they alert pilots of a too-steep climb that could result in an aerodynamic stall. In the case of the Lion Air flights, the left-side sensor was showing the nose pointed about 20 degrees higher than was actually the case. BLOOMBERG