Boeing crash clues raise new questions
Investigators are slowly piecing together clues of how Indonesia’s worst air disaster in two decades transpired, raising questions over how a near brand-new Boeing jet that had recurring instrument failures was cleared for its ill-fated flight.
The Lion Air Max 8 plane’s angle-of-attack sensor, which helps aircraft maintain the correct pitch to stay airborne, was replaced the day before the October 29 crash after erroneous readings on a previous trip, the Indonesia National Transportation Safety Committee said this week. Faulty airspeed readings plagued the jet on its last four flights before it plunged into the Java Sea with 189 people aboard.
The revelations spurred Boeing to alert operators of the 737 Max aircraft worldwide that the airflow sensor can provide false readings in certain circumstances. Misleading data from that device could trick the plane into pointing its nose down.
That warning and the investigation team’s statement suggest the pilots on JT610 may have been battling with the aircraft as its computers commanded a dive. In addition, the faulty cockpit data over multiple flights leading up to the accident and the replacement of a wildly misleading sensor have raised questions about maintenance, oversight and the plane’s suitability for service.
“The aircraft, with that recurring problem, should not have been released to fly,” Neil Hansford, chairman of Australian consultancy firm Strategic Aviation Solutions who has worked with airlines worldwide for more than 30 years, said. “It should have been grounded.”
The almost brand-new plane, with just 800 hours of flight time, was cleared for the October 29 flight after maintenance overnight, Lion Air has said.
On a previous flight from Bali to Jakarta, the same jet’s angle-of-attack sensor feeding the captain’s displays registered a 20-degree difference from the device on the copilot’s side of the cockpit, the committee said. The malfunction can cause the computers to erroneously detect a midflight stall in airflow, triggering a dive to regain speed to keep flying.
Moments into the aircraft’s final flight, the pilots asked to return to Jakarta but never turned back, according to Indonesia’s safety commission and flight-tracking data. Shortly afterward, JT610 plunged into the water, nosing downward so suddenly that it may have hit speeds of 1000km/h.
Investigators will want to examine the pilots’ actions, how flight crews were trained and whether maintenance that was performed was adequate, said Roger Cox, a former US National Transportation Safety Board investigator.
“I would definitely be looking at the man-machine interface and how pilots respond,” said Cox, a former airline pilot who flew earlier versions of the 737.