SYNOPSIS

On 28 October 2018, a Boeing 737-8 (MAX) aircraft registered PK-LQP was being operated by PT. Lion Mentari Airlines (Lion Air) as a scheduled passenger flight from I Gusti Ngurah Rai International Airport (WADD), Denpasar to Jakarta as LNI043. During pre-flight check, the PIC discussed with the engineer of the maintenance actions that had been performed including replacement of the AoA sensor and had been tested accordingly.

The aircraft departed at 1420 UTC (2220 LT) at night time, the DFDR showed the stick shaker activated during the rotation and remained active throughout the flight. About 400 feet, the PIC noticed on the PFD the IAS DISAGREE warning appeared. The PIC handed over control to the SIC and cross checked the PFDs with the standby instrument and determined that the left PFD had the problem. The PIC noticed the aircraft was automatically trimming AND. The PIC moved the STAB TRIM switches to CUT OUT and the SIC continued the flight with manual trim without auto-pilot until the end of the flight.

The PIC declared “PAN PAN” to the Denpasar Approach controller due to instrument failure and requested to maintain runway heading. The PIC performed three Non-Normal Checklists and none contained the instruction “Plan to land at the nearest suitable airport”.

The remainder of the flight was uneventful and the aircraft landed Jakarta about 1556 UTC. After parking, the PIC informed the engineer about the aircraft problem and entered IAS and ALT Disagree and FEEL DIFF PRESS problem on the AFML.

The engineer performed flushing the left Pitot Air Data Module (ADM) and static ADM to rectify the IAS and ALT disagree followed by operation test on ground and found satisfied. The Feel Differential Pressure was rectified by performed cleaned electrical connector plug of elevator feel computer. The test on ground found the problem had been solved.

At 2320 UTC, (0620 on 29 October 2018 LT), the aircraft departed from Jakarta with intended destination of Pangkal Pinang. The DFDR recorded a difference between left and right AoA of about 20° and continued until the end of recording. During rotation the left control column stick shaker activated and continued for most of the flight.

During the flight the SIC asked the controller to confirm the altitude of the aircraft and later also asked the speed as shown on the controller radar display. The SIC reported experienced„flight control problem‟.

After the flaps retracted, the DFDR recorded automatic AND trim active followed by flight crew commanded ANU trim. The automatic AND trim stopped when the flaps extended. When the flaps retracted to 0, the automatic AND trim and flight crew commanded ANU trim began again and continued for the remainder of the flight. At 23:31:54 UTC, the DFDR stopped recording.

Until the publishing of this Preliminary Report, the CVR has not been recovered, the search for CVR is continuing. The investigation will perform several tests including the test of the AoA sensor and the aircraft simulator exercises in the Boeing engineering simulator. The investigation has received the QAR data for flight for analysis.

The investigation involved the NTSB of the United States of America as State of design and State of manufacturer, the TSIB of Singapore and the ATSB of Australia as State provide assistant that assigned accredited representatives according to ICAO Annex 13.

1 History of the Flight

On 29 October 2018, a Boeing 737-8 (MAX) aircraft registered PK-LQP was being operated by PT. Lion Mentari Airlines (Lion Air) as a scheduled passenger flight from Soekarno-Hatta International Airport (WIII), Jakarta1 with intended destination of Depati Amir Airport (WIPK), Pangkal Pinang2. The scheduled time of departure from Jakarta was 0545 LT (2245 UTC3 on 28 October 2018) as LNI610.

At 2320 UTC, the aircraft departed from Jakarta using runway 25L and intended cruising altitude was 27,000 feet. The LNI610 pilot was instructed to follow the Standard Instrument Departure (SID) of ABASA 1C4.

According to the weight and balance sheet, on board the aircraft were two pilots, five flight attendants and 181 passengers consisted of 178 adult, one child and two infants. The voyage report5 showed that the number of flight attendant on board was six flight attendants.

The Digital Flight Data Recorder (DFDR) recorded a difference between left and right Angle of Attack (AoA)6 of about 20° and continued until the end of recording. During rotation the left control column stick shaker7 activated and continued for most of the flight.

Shortly after departure, the Jakarta Tower controller instructed LNI610 to contact Terminal East (TE) controller. At 23:21:22 UTC, the LNI60 SIC made initial contact with the TE controller who responded that the aircraft was identified on the controller Aircraft Situational Display/ASD (radar display). Thereafter, the TE controller instructed the LNI610 to climb to altitude 27,000 feet.

At 23:21:28 UTC, the LNI610 SIC asked the TE controller to confirm the altitude of the aircraft as shown on the TE controller radar display. The TE controller responded that the aircraft altitude was 900 feet and was acknowledged by the LNI610 Second in Command (SIC).

At 23:21:53 UTC, the LNI610 SIC requested approval to the TE controller “to some holding point”. The TE controller asked the LNI610 the problem of the aircraft andthe pilot responded “flight control problem”.

The LNI610 descended from altitude 1,700 to 1,600 feet and the TE controller then asked the LNI610 of the intended altitude. The LNI610 SIC advised the TE controller that the intended altitude was 5,000 feet.

At 23:22:05 UTC, the DFDR recorded the aircraft altitude was approximately 2,150 feet and the flaps were retracted. After the flaps reached 0, the DFDR recorded automatic aircraft nose down (AND) trim active for 10 seconds followed by flight crew commanded aircraft nose up (ANU) trim.

At 23:22:31 UTC, the TE controller instructed the LNI610 to climb and maintain altitude of 5,000 feet and to turn left heading 050°. The instruction was acknowledged by the LNI610 SIC.

At 23:22:48 UTC, the flaps extended to 5 and the automatic AND trim stopped.

At 23:22:56 UTC, the LNI610 SIC asked the TE controller the speed as indicated on the radar display. The TE controller responded to the LNI610 that the ground speed of the aircraft shown on the radar display was 322 knots.

At 23:24:51 UTC, the TE controller added “FLIGHT CONT TROB” text for LNI610 target label on the controller radar system as reminder that the flight was experiencing flight control problem.

At 23:25:05 UTC, the TE controller instructed the LNI610 to turn left heading 350° and maintain altitude of 5,000 feet. The instruction was acknowledged by the LNI610 SIC.

At 23:25:18 UTC, the flaps retracted to 0. At 23:25:27 UTC, the automatic AND trim and flight crew commanded ANU trim recorded began again and continued for the remainder of the flight.

At 23:26:32 UTC, the TE controller instructed the LNI610 to turn right heading 050° and maintain altitude of 5,000 feet. The instruction was acknowledged by the LNI610 SIC.

At 23:26:59 UTC, the TE controller instructed the LNI610 to turn right heading 070° to avoid traffic. The LNI610 pilot did not respond to the TE controller‟s instruction, thereafter, the controller called the LNI610 twice who responded at 23:27:13 UTC.

At 23:27:15 UTC, the TE controller instructed the LNI610 to turn right heading 090° which was acknowledged by the LNI610 SIC. A few second later, the TE controller revised the instruction to stop the turn and fly heading 070° which was acknowledged by the LNI610 SIC.

At 23:28:15 UTC, the TE controller provided traffic information to the LNI610 who responded “ZERO”. About 14 seconds later, the TE controller instructed the LNI610 to turn left heading 050° and maintain an altitude of 5,000 feet. The instruction was acknowledged by the LNI610 SIC.

At 23:29:37 UTC, the TE controller questioned the LNI610 whether the aircraft was descending as the TE controller noticed that the aircraft was descending. The LNI610 SIC advised the TE controller that they had a flight control problem and were flying the aircraft manually.

At 23:29:45 UTC, the TE controller instructed the LNI610 to maintain heading 050° and contact the Arrival (ARR) controller. The instruction was acknowledged by the LNI610 SIC.

At 23:30:03 UTC, the LNI610 contacted the ARR controller and advised that they were experiencing a flight control problem. The ARR controller advised LNI610 to prepare for landing on runway 25L and instructed them to fly heading 070°. The instruction was read back by the LNI610 SIC.

At 23:30:58 UTC, the LNI610 SIC stated “LNI650 due to weather request proceed to ESALA8” which was approved by the ARR controller.

At 23:31:09 UTC, the LNI610 PIC advised the ARR controller that the altitude of the aircraft could not be determined due to all aircraft instruments indicating different altitudes. The pilot used the call sign of LNI650 during the communication. The ARR controller acknowledged then stated “LNI610 no restriction”.

At 23:31:23 UTC, the LNI610 PIC requested the ARR controller to block altitude 3,000 feet above and below for traffic avoidance. The ARR controller asked what altitude the pilot wanted. At 23:31:35 UTC, the LNI610 PIC responded “five thou”. The ARR controller approved the pilot request.

At 23:31:54 UTC, the FDR stopped recording.

The ARR controller attempted to contact LNI610 twice with no response. At 23:32:19 UTC, the LNI610 target disappeared from the ASD and changed to flight plan track. The ARR controller and TE controller attempted to contact LNI610 four more times with no response.

The ARR controller then checked the last known coordinates of LNI610 and instructed the assistant to report the occurrence to the operations manager.

The ARR controller requested several aircraft to hold over the last known position of LNI610 and to conduct a visual search of the area.

About 0005 UTC (0705 LT), tug boat personnel found floating debris at 5°48’56.04″S; 107° 7’23.04″E which was about 33 Nm from Jakarta on bearing 56°. The debris was later identified as LNI610.

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