The Indonesian National Transportation Safety Committee (NTSC) has published its preliminary aircraft accident investigation report on Lion Air flight JT610 which crashed on 29 October 2018.
The preliminary report is based upon initial investigation carried out by the NTSC in accordance with national and international civil aviation regulations. It contains factual information which was collected after the crash until publication of the interim report. It does not include an analysis and conclusion.
Lion Air flight JT610, operated with Boeing 737 MAX8 PK-LQP, took off from Jakarta airport on 29 October 2018 at 06:20 local time (23:20 UTC) with destination Pangkal Pinang. The flight had 181 passengers on board as well as 8 flight crew members. About 11 minutes after takeoff, the aircraft crashed into the sea. There were no survivors and the aircraft was destroyed (see No survivors on Lion Air Boeing 737 MAX 8 flight JT610 that crashed into sea near Java).
As stated, this preliminary report does not make any conclusions nor any analysis. Nevertheless, there are many findings, some of which may have attributed to the crash of flight JT610. Here are for example some findings of the previous flight with the ill-fated aircraft:
- The stick shaker activated during the rotation and remained active throughout the flight. About 400 feet, the pilot in command (PIC) noticed on the Primary Flight Display (PFD) that the IAS DISAGREE warning appeared.
- The PIC cross-checked both PFDs with the standby instrument and determined that the left PFD had the problem. The flight was handled by the SIC.
- The PIC noticed that as soon the SIC stopped trim input, the aircraft was automatically trimming aircraft nose down (AND). After three automatic AND trim occurrences, the SIC commented that the control column was too heavy to hold back. The PIC moved the STAB TRIM switches to CUT OUT.
- The pilot performed three Non-Normal Checklists (NNCs).
- Eventually, the aircraft landed at Jakarta.
A full list of findings is available in the preliminary report.
Furthermore, the report highlights some of the safety actions that have already been taken by several parties, including Lion Air, the Boeing Company and the Federal Aviation Administration (FAA). Some of these safety actions are:
- On 29 October 2018 Lion Air issued a safety reminder to all Boeing 737 pilots to review several procedures including memory items of airspeed unreliable and runaway stabilizer.
- On 6 November 2018 the Boeing Company issued Flight Crew Operation Manual Bulletin (OMB) Number TBC-19 with subjected Un-commanded Nose Down Stabilizer Trim Due to Erroneous Angle of Attack (AOA) During Manual Flight Only to emphasize the procedures provided in the runaway stabilizer non-normal checklist (NNC).
- On 7 November 2018, the FAA issued Emergency Airworthiness Directive (AD) Number 2018-23-51 for the owners and operators of the Boeing 737-8 and -9 aircraft.
Finally, the preliminary report also contains safety recommendations that were already issued by the NTSC of Indonesia. These include:
- Refer to the CASR Part 91.7 Civil Aircraft Airworthiness and the Operation Manual part A subchapter 1.4.2, the pilot in command shall discontinue the flight when un-airworthy mechanical, electrical, or structural conditions occur.
- The flight from Denpasar to Jakarta experienced stick shaker activation during the takeoff rotation and remained active throughout the flight. This condition is considered as un-airworthy condition and the flight shall not be continued.
- KNKT recommend ensuring the implementation of the Operation Manual part A subchapter 1.4.2 in order to improve the safety culture and to enable the pilot to make proper decision to continue the flight.
We may interpret these safety recommendations in such a way that the previous flight from Denpasar to Jakarta should not have continued its flight and should have made a precautionary landing at the nearest suitable airport instead of continuing the flight to Jakarta. The report, however, does not explicitly state if the aircraft was still un-airworthy to operate the flight from Jakarta to Pangkal Pinang, since maintenance actions were performed in Jakarta. But as stated, the preliminary report does not make any analysis and conclusions.
The preliminary report is available here (pdf).
28 November 2018
Photos: © NTSC
Boeing statement on Lion Air flight JT610 preliminary report
The Boeing Company is deeply saddened by the loss of Lion Air Flight 610. We extend our heartfelt condolences and sympathies to the families and loved ones of those onboard.
Safety is a core value for everyone at Boeing and the safety of our airplanes, our customers’ passengers and their crews is always our top priority. As our customers and their passengers continue to fly the 737 MAX to hundreds of destinations around the world every day, they have our assurance that the 737 MAX is as safe as any airplane that has ever flown the skies.
Boeing appreciates Indonesia’s National Transportation Safety Committee (NTSC) for its ongoing efforts to investigate the causes of the accident. Boeing is taking every measure to fully understand all aspects of this accident, working closely with the U.S. National Transportation Safety Board as technical advisors to support the NTSC as the investigation continues.
Earlier today, the NTSC released its preliminary accident investigation report. The report provides detailed accounts of Flight 610 and of the immediately preceding flight of the same aircraft.
The report explains that the maintenance logs for the accident aircraft recorded problems related to airspeed and altitude on each of the four flights that occurred over the three days prior to Flight 610. The logs indicate that various maintenance procedures were performed, but issues related to airspeed and altitude continued on each successive flight. The logs indicate that, among other procedures, on Oct. 27, two days prior to the incident flight, one of the airplane’s Angle of Attack (AOA) sensors was replaced.
On Oct. 28, before the flight immediately prior to Flight 610, the pilot in command and the maintenance engineer discussed the maintenance that had been performed on the aircraft. The engineer informed the pilot that the AOA sensor had been replaced and tested. The report does not include records as to the installation or calibration of the new sensor, nor does the report indicate whether the sensor was new or refurbished. Although the report states that the pilot was satisfied by the information relayed by the engineer that the AOA sensor had been replaced and tested, on the subsequent flight the pilots again experienced problems with erroneous airspeed data, and also experienced automatic nose down trim.
The report states that the flight crew of the Oct. 28 flight turned off the stabilizer trim switches within minutes of experiencing the automatic nose down trim, and continued with manual trim through the end of the flight. The report further notes that the pilot performed three non-normal checklist procedures, including the runaway stabilizer non-normal checklist, which is a memory item prescribed by the 737 MAX Flight Crew Operations Manual, and reaffirmed in Boeing Flight Crew Operations Manual Bulletin TBC-19 and FAA Emergency Airworthiness Directive (AD) Number 2018-23-51, as the appropriate procedure to address unintended horizontal stabilizer movement, regardless of source.
The report indicates that the remainder of the Oct. 28 flight was uneventful and that the flight continued to its destination. The report also states that, after landing, the pilot reported some of the experienced issues both on the aircraft maintenance log and to engineering. The report states that the pilot ran the runaway stabilizer non-normal check list, but it does not state that he communicated that fact in the maintenance documentation following that flight.
The following day, Oct. 29, shortly after taking off, the pilots experienced issues with altitude and airspeed data that the pilots had previously experienced on the earlier flights, due to erroneous AOA data. Data from the flight data recorder summarized in the report also makes clear that, as on the previous flight, the airplane experienced automatic nose down trim. In response, the flight crew repeatedly commanded nose up trim. This sequence repeated for the remainder of the flight, during which the flight crew was able to maintain control of the airplane for approximately ten minutes. Unlike as is stated with respect to the prior flight, the report does not state whether the pilots performed the runaway stabilizer procedure or cut out the stabilizer trim switches.
In accordance with international protocol, all inquiries about the ongoing accident investigation must be directed to the NTSC.
