Indonesia’s National Transportation Safety Committee on Wednesday (Nov. 28) will release a preliminary report on the crash of Lion Air JT610, which plunged into the Java Sea shortly after takeoff, killing all 189 people on board.
The report will be made public at its offices at 10am local time, the committee, known by the acronym KNKT, said via email. It should be available here after its release.
Lion Air JT610 set off at 6:20am on Oct. 29 from Jakarta to Pangkal Pinang, near the island of Sumatra, and crashed less than 15 minutes after takeoff. The pilots had requested to turn back about 12 miles (19km) out from takeoff, but did not signal there was an emergency, a spokesman for AirNav Indonesia, which oversees air traffic navigation in the country, told CNN. The aircraft, a new Boeing 737 Max 8, had reported trouble with a flight speed sensor and experienced erratic altitudes and speeds on a previous flight. The plane’s flight data recorder was recovered on Nov. 4, but its cockpit voice recorder has not been recovered.
Indonesian investigators first focused on a malfunctioning airspeed indicator, and then began to examine a new anti-stall system in the craft that adjusts the plane’s nose down when an “angle of attack” sensor indicates that it may not be able to maintain lift. In certain conditions, that adjustment might be quite sharp and unexpected, the Wall Street Journal has reported (paywall).
On Nov. 6, Boeing put out a worldwide safety bulletin directing operators to procedures for dealing with faulty angle sensor data that could trigger such a movement. The following day, the US Federal Aviation Administration ordered fleets to update their training manuals with information on how to adjust for the feature in Max 8 and 9 planes (pdf). The US’s largest pilot unions have said the information in those directives led them to realize (paywall) they had not been informed of the new feature on the 737 Max.
Boeing says it is working closely with regulators and investigators to understand the factors leading to the crash. It has also disputed the unions’ statements that the new feature wasn’t adequately publicized. Globally, airlines have ordered almost 4,800 of the aircraft from Boeing. Lion Air has ordered more than 200 of the new 737 Max’s.
On Friday (Nov. 23), Nurcahyo Utomo, the head of KNKT’s aircraft accident investigation subcommittee, told Indonesia’s parliament that the flight recorder showed the pilot and co-pilot received different airspeed readings, and that at 5,000 feet the automatic trim—the downward adjustment—triggered. The pilot fought hard against the automatic trim but was unable to counter it, Utomo said.
Indonesia has long had a troubled air safety record—the October crash came only a few months after the European Union removed all of the country’s airlines from its safety blacklist. The Lion Air tragedy is the worst air disaster in Indonesia since a Garuda Indonesia plane crashed in 1997, killing the 234 people on board.