B38M, en-route, northeast of Jakarta Indonesia, 2018
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|On 29 October 2018, a Lion Air Boeing 737-MAX 8 crew had difficulty controlling the aircraft in pitch almost immediately after a day takeoff from Jakarta. After failing to resolve the problem, the crew decided to return to the departure airport. No abnormal or emergency status was declared, but after approximately 11 minutes airborne, contact was lost and it was found that sea surface impact had destroyed the aircraft. Successful management of apparently similar pitch control problems during the aircraft’s previous flight, after which there had been maintenance input before release to service for the accident flight, has been noted. The Investigation is continuing.|
|Actual or Potential
|Loss of Control|
|Flight Conditions||Not Recorded|
|Aircraft||BOEING 737 MAX 8|
|Type of Flight||Public Transport (Passenger)|
|Origin||Jakarta/Soekarno-Hatta International Airport|
|Intended Destination||Depati Amir Airport|
|Take off Commenced||Yes|
|ICL / ENR|
|Origin||Jakarta/Soekarno-Hatta International Airport|
|Destination||Depati Amir Airport|
|Approx.||the last recorded FDR position|
|Tag(s)||Significant Systems or Systems Control Failure|
|Damage or injury||Yes|
|Aircraft damage||Hull loss|
|Fatalities||Most or all occupants (189)|
On 29 October 2018, a Boeing 737-MAX 8 (PK-LQP) being operated by Indonesian carrier Lion Air on a scheduled domestic passenger flight from Jakarta Soekarno-Hatta to Pangkal Pinang as LNI 610 impacted the sea northeast of Jakarta approximately 11 minutes after its day takeoff. The pilots had reported a flight control problem to ATC radar and requested and begun a return to Jakarta, but no declaration of urgency or emergency was made. Evidence indicating that the aircraft had broken up after impact with the sea surface was found soon after the last recorded transmission to ATC. The aircraft was destroyed and none of the 189 occupants survived.
It was noted that the 31-year-old Captain, an Indian national, had a total of 6,028 hours flying experience including 5,176 hours on type and that the 41-year-old First Officer, an Indonesian national, had a total of 5,174 hours flying experience including 4,286 hours on type. In both cases, not all the ‘on type’ hours were gained on the specific type variant involved in the accident. It was also noted that at the time of the accident, Lion Air were operating a total of 117 aircraft including 10 examples of the Boeing 737 - MAX variant.
It has been established that the crew of a flight into Jakarta earlier the previous evening local time, which preceded the departure of the accident flight, had experienced both a faulty left hand IAS display and a stabiliser trim runway. Both problems had been dealt with by following existing procedures so that they were able to safely complete their flight, although with a precautionary declaration of PAN status. On arrival at Jakarta, fault entries were made by the Captain in both the aircraft Technical Log and the Company ‘Electronic Reporting System’ maintenance intervention was followed by release to service for the departure to Pangkal Pinang the next morning after just over 7 hours on the ground.
As soon as the accident flight became airborne from runway 25L, DFDR data showed that there had been a difference between left and right AoA of about 20° which had continued until the end of recording. DFDR data also showed that at no point in the flight had either AP been engaged and that during rotation the left control column stick shaker (only) had activated and this had continued, apart from one 20 second interval, until the end of recording. At no time was the right control column stick shaker activated.
After transfer from TWR to the initial departure frequency, the aircraft was identified and cleared to climb to FL 270. Almost immediately, the First Officer asked the controller to advise the altitude of the aircraft as shown on the ATC radar display and was told this was 900 feet, which was acknowledged. Soon after this exchange, one of the pilots requested that the aircraft be cleared to proceed “to some holding point” and when the controller asked what the problem was, he received the reply “flight control problem”. When the controller observed the aircraft beginning to descend from an altitude of 1700 feet, he asked the crew what their intended altitude was and was told by the First Officer “5000 feet”. The aircraft began to climb, and DFDR data showed that the flaps were selected up. When they reached zero, the DFDR recorded 10 seconds of automatic nose down followed by flight crew commanded aircraft nose up trim. The flaps were then extended to 5° and the automatic nose down trim ceased. The First Officer then asked the controller what the indicated speed of the aircraft was on the radar display and was informed that the ground speed shown was 322 knots The controller subsequently added a label “FLIGHT CONT PROB” against the aircraft to serve as a reminder. Approximately 2½ minutes after the flaps had been selected to 5°, they were reselected to zero. When they reached that position, DFDR data showed that both automatic and flight crew commanded nose up trim had commenced and had continued for the remainder of the flight - a further 5½ minutes.
After observing the aircraft reaching approximately 5000 feet, the controller instructed the crew to maintain this altitude and continued to issue radar headings which, after an initial left turn downwind from the runway extended centreline, had been generally northeasterly and had taken the aircraft over the sea and away from the airport. Observing that the aircraft's indicated altitude on the radar screen was reducing, the controller had queried this and received the response from the First Officer that they still had a flight control problem and were flying the aircraft manually. He then transferred the aircraft to the Arrival frequency, where the crew again advised on checking in that they had a flight control problem and were told to expect an approach to runway 25L and given a radar heading of 070°. The First Officer then requested a deviation right to proceed to waypoint ESALA (see the ground track illustration below) for weather avoidance which was approved. This approval was immediately followed by the Captain advising the controller that “the altitude of the aircraft could not be determined due to all aircraft instruments indicating different altitudes” to which the controller responded “no restriction.” The Captain followed up with a request to the controller to “block altitude 3,000 feet above and below for traffic avoidance” to which the controller responded by asking what altitude was required and the Captain replied with “five thou” which was approved. There were no further communications on the R/T and about fifteen seconds later, the DFDR recording ceased. About 35 minutes later, a boat in the vicinity reported finding floating debris about 33 nm from Jakarta on a bearing of 056°; the debris subsequently identified as being from the accident aircraft. Wreckage that has been recovered subsequently is from all parts of the aircraft structure and indicated that a high energy impact had occurred.
It was noted that both the Civil Aviation Safety Regulations (CASR) Part 91.7 ‘Civil Aircraft Airworthiness’ and the Lion Air Operations Manual Part ‘A’ General contained an explicit requirement that the pilot-in-command “must discontinue the flight when un-airworthy mechanical, electrical, or structural conditions occur”.
The flight from Denpasar to Jakarta previous to the accident flight was fully recorded on the DFDR and the investigation has already reviewed what happened before, during and after it. It was found that the Captain was aware that maintenance had been working on the aircraft and had replaced the left AoA sensor. During the departure briefing, he advised that he would be PF and included mention of the AoA sensor replacement. DFDR data showed that the stick shaker had activated during rotation and had thereafter remained active throughout the flight. The Captain had initially maintained the normal 15° pitch and the takeoff thrust setting before handing over control to the First Officer and announcing “memory item airspeed unreliable”. A cross-check of the two PFDs with the standby instrument showed that the left PFD had the problem and the Captain then selected the right side FD so that the First Officer, now PF, would have a normal flight instrument display. The Captain directed that acceleration and flap retraction should continue as normal with the First Officer following the FD command and re-trimming the aircraft as required.
The Captain reported then noticing that as soon as the First Officer stopped trim inputs, the aircraft began automatically trimming nose down. After three of these automatic trim occurrences, the First Officer stated that the control column was too heavy to hold back and the Captain declared a PAN to ATC advising instrument failure and requesting to remain on runway heading. This was approved. The controller asked if they wanted to return and received a ‘Standby’ response. The Captain then moved the STAB TRIM switches to CUT OUT, which solved the problem, and he decided to continue and complete the flight without engaging the AP and using manual trim. Three Abnormal Checklists were completed - ‘Airspeed Unreliable’, ‘ALT DISAGREE’, and ‘Runaway Stabiliser’ noting that none of these included a requirement to “land at the nearest suitable airport” but aware that the aircraft was no longer RVSM compliant. When climb clearance to FL 380 was given en route, the Captain declared a ‘PAN’ due to instrument failure and having requested a non-RVSM cruise altitude instead of the cleared FL 380, was given FL 280. The controller then requested more details of the instrument failure and was informed that there had been “an altitude and autopilot failure” and asked to relay to the Jakarta controller a request for an uninterrupted descent.
The flight was completed without further event and the Captain then made an Aircraft Technical Log Defect entry stating “IAS (Indicated Air Speed) and ALT (altitude) Disagree and FEEL DIFF PRESS (Feel Differential Pressure) light”. He also reported the defective condition using the Company’s electronic reporting system as follows “Airspeed unreliable and ALT disagree shown after takeoff, Speed Trim System also running to the wrong direction, suspected because of speed difference, identified that CAPT instrument was unreliable and handover control to FO. Continue NNC of Airspeed Unreliable and ALT disagree. Decide to continue flying to CGK at FL280, landed safely runway 25L.”
It was found that in response to these reported defects, the maintenance engineer on duty had flushed the left pitot air data module (ADM) and the static ADM to rectify the IAS and ALT disagree and then performed a successful system ground operation test. He had also rectified the differential pressure problem by cleaning the electrical connector plug of the elevator feel computer and then carrying out a satisfactory system ground test.
The Investigation examined the other defect entries in the accident aircraft Technical Log recorded between 26 October and 29 October and found that several related to indicated airspeed. The altitude flag had appeared on the left side PFD on three occasions, SPEED TRIM FAIL and MACH TRIM FAIL had appeared on that side twice.
Safety Action taken as a result of the accident and known to the Investigation has included but has not been limited to the following:
- The Boeing Company issued FCOM Bulletin (OMB) Number TBC-19 on 6 November 2018 on ‘un-commanded nose down stabilizer trim due to erroneous Angle of Attack during manual flight only’ to emphasise the procedures provided in the runaway stabiliser Abnormal Checklist. On 11 November 2018, they also issued a Multi Operator Message (MOM) on ‘Multi Model Stall Warning and Pitch Augmentation Operation’.
- The Federal Aviation Administration issued an Emergency AD 2018-23-51 in respect of all Boeing 737-8 MAX and 737-9 MAX aircraft on 7 November 2018 which required, within three days of receipt, revisions to the certificate limitations and operating procedures contained in the AFM to provide flight crews with “runaway horizontal stabiliser trim procedures to follow under certain conditions”. The FAA noted the AD was “prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AoA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabiliser”. The FAA also stated in the AD that it had been issued because excessive nose-down attitude, significant altitude loss in this situation “could cause the flight crew to have difficulty controlling the airplane and lead to […] significant altitude loss and possible impact with terrain”.
- Lion Air has issued a reminder to all its 737 pilots to ensure that they have a thorough understanding of any Deferred Maintenance Item for the aircraft accepted for flight, to check the Aircraft Technical Log for any previous defect and the action taken in respect of it before flight, to be ready for any abnormal or emergency conditions by having Memory Items and manoeuvres reviewed and to record any malfunctions that have occurred during a flight in the aircraft Technical Log and brief the duty engineer comprehensively about them, referring as necessary to the Fault Reporting Manual provided in the aircraft.
- Lion Air has instructed all its 737 pilots to use the Fault Reporting Manual when recording defects in the Aircraft Technical Log and to ensure that they provide sufficient detail in the entry.
- Lion Air has reinforced the current pilot simulator training for all fleets in respect of “Unreliable Airspeed” and “Stabiliser Runaway” manoeuvres with immediate effect and re-emphasised, by issue of a Notice to Pilots, ground recurrent training and simulator sessions on the decision making process applicable to the declaration of an abnormal (PAN-PAN) or emergency (MAYDAY-MAYDAY) condition.
- Lion Air have instructed their Maintenance Directorate to ensure that Batam Aero Technic (BAT) reinforce the role of the technical specialist team as line maintenance support for more efficient troubleshooting process so that “live” malfunctions are properly followed up until properly solved. They are also to ensure that BAT provides adequate alerting on repetitive defects even though reports for a malfunction may have been coded under different ATA references and are to reinforce the role of the Maintenance Control Centre in malfunction follow up and troubleshooting.
- Lion Air have instructed their pilots to follow the guidance contained in Boeing 737 FCOM Bulletins TBC-19 and MLI-15 and instructed their ‘Corporate Safety Director’ and the Director of Batam Aero Technic (BAT) to implement DGAC AD 18-11-011-U.
- Batam Aero Technic (BAT) have issued instructions to revise the Boeing 737-8 MAX AFM in accordance with Indonesian DGCA AD 18-11-011-U, which reflects the requirements of the FAA AD, and have also conducted Angle of Attack installation tests on all Boeing 737-8 MAX aircraft operated by Lion Air.
The Investigation is continuing. On the basis of the work so far two Safety Recommendations have been issued as follows:
- that Lion Air should ensure the implementation of the Operations Manual Part ‘A’, subchapter 1.4.2 (which requires the pilot in command to discontinue the flight when un-airworthy mechanical, electrical, or structural conditions occur) in order to improve the safety culture and to enable pilots to make a proper decision to continue a flight.
- that Lion Air should ensure that all operational documents (such as the weight and balance sheet which did not show the correct crew complement for the accident flight) are properly completed.
A Preliminary Report of progress in the Investigation was published on 28 November 2018.
- Loss of Control
- Unreliable Airspeed Indications
- Flight Controls
- Trim Systems
- Emergency Communications
- FCOM Bulletin (OMB) Number TBC-19: Un-commanded nose down stabilizer trim due to erroneous Angle of Attack during manual flight only, Boeing, 6 November 2018
- Multi Operator Message (MOM) on ‘Multi Model Stall Warning and Pitch Augmentation Operation’, Boeing, 11 November 2018
- Emergency AD 2018-23-51, FAA, 7 November 2018