Lion Air Flight 610

Lion Air Flight 610 was a scheduled domestic passenger flight from Soekarno–Hatta International Airport, Tangerang, to Depati Amir Airport, Pangkal Pinang, in Indonesia. On 29 October 2018, the Boeing 737 MAX 8 operating the route, carrying 181 passengers and 8 crew members, crashed into the Java Sea 11 minutes after takeoff, killing all 189 occupants on board. It was the first major accident and hull loss of a 737 MAX, a then recently introduced aircraft.

It is the deadliest accident involving the Boeing 737 family, surpassing Air India Express Flight 812 in 2010. It was the deadliest accident in Lion Air's history, surpassing the 2004 Lion Air Flight 538 crash that killed 25, the deadliest aircraft accident in Indonesia since Garuda Indonesia Flight 152 in 1997, and the deadliest aircraft accident in the Java Sea, surpassing Indonesia AirAsia Flight 8501 in 2014.

The Indonesian government's search and rescue found debris and human remains soon after from a 280 km area. The first victim was identified two days after the crash. The flight data recorder (FDR) was found on 1 November and recovered for analysis. One diver also died during recovery operations.

The subsequent investigation, led by the National Transportation Safety Committee (NTSC), revealed that a new software function in the flight control system caused the aircraft to nose down. That function, the Maneuvering Characteristics Augmentation System (MCAS), had been intentionally omitted by Boeing from aircraft documentation for aircrews, so the Lion Air pilots did not know about it nor did they know what it could do. Investigators concluded that an external device on the aircraft, the angle-of-attack (AoA) sensor, was miscalibrated due to improper maintenance which sent erroneous data to MCAS. In turn, MCAS responded by pushing the nose down. The problem had occurred on the same aircraft during its immediately preceding flight, and the pilots had recovered using a standard checklist for such a "runaway stabilizer" condition.

During the accident flight, the AoA sensor again fed erroneous data to the MCAS, which pushed the nose of the aircraft down. The pilots did not properly follow the checklist, with the result that MCAS remained active and repeatedly put the aircraft into an unsafe nose-down position until it crashed into the water.

After the accident, the United States Federal Aviation Administration and Boeing issued warnings and training advisories to all operators of the Boeing 737 MAX series, reminding pilots to follow the runaway stabilizer checklist to avoid letting the MCAS cause similar problems. The company also said that a software update would be made available to update the behavior of MCAS. Despite these advisories, similar issues caused the crash of Ethiopian Airlines Flight 302 on 10 March 2019, prompting a worldwide grounding of all 737 MAX aircraft.

The final report by the National Transportation Safety Committee (NTSC) of Indonesia criticized Boeing's design and the FAA's certification process for MCAS and said the issues were compounded by maintenance issues and lapses by Lion Air's repair crews and its pilots, as well as Xtra Aerospace, a US-based company that supplied Lion Air with the AoA sensor.

Flight details and accident

The aircraft took off from Jakarta on 29 October 2018 at 6:20 am local time (28 October 2018, 11:20 pm UTC) and was scheduled to arrive at Depati Amir Airport in Pangkal Pinang at 7:20 am. It took off in a westward direction before circling around to a northeast heading, which it held until crashing offshore northeast of Jakarta in waters estimated to be as much as 35 m deep. The flight crew had requested clearance to return to the Jakarta airport 19 nmi into the flight. The accident site was located 34 km off the coast of the island of Java.

Communication between air traffic control (ATC) and Flight 610 was suddenly lost at 6:33 am. ATC informed the National Search and Rescue Agency, which deployed three ships and a helicopter to the area. At 7:30 am, the agency received reports that Flight 610 had crashed a few kilometres from an offshore oil platform. Workers on the platform reportedly saw the aircraft crash with a steep nose-down angle. Boats from the platform were immediately deployed and debris from the crashed aircraft was found shortly after.

Flight abnormalities

Aviation experts noted some abnormalities were seen in the altitude and the airspeed of Flight 610. Just three minutes into the flight, the captain asked the controller for permission to return to the airport as the aircraft had flight-control problems. About eight minutes into the flight, data transmitted automatically by the aircraft showed it had descended to about 5000 ft, but its altitude continued to fluctuate. The mean value of the airspeed data transmitted by Flight 610 was around 300 kn, which was considered by experts to be unusual, as typically aircraft at altitudes lower than 10000 ft are restricted to an airspeed of 250 kn. Ten minutes into the flight, the data recorded the aircraft dropping by more than 3000 ft. The last recorded altitude of the aircraft was 2500 ft.