09 Jan 2021 - 737-500, PK-CLC (27323/2616), FF 13/5/1994 (27 Years old), operated by Sriwijaya Air on flight SJ-182 from Jakarta to Pontianak has crashed into the Java Sea 5 minutes after take off. No Mayday call was made.
There were 50 passengers and 12 crew on board.
The aircraft had been in storage from 23 March to 19 December 2020 because of the COVID-19 empidemic but had been flying for several weeks before the accident.
Three findings stood out to me in the preliminary report (see below for full details):
The preliminary report found that after the aircraft climbed past 8,150 feet, the thrust lever position of the left engine started reducing, while the thrust lever position of the right engine remained. The FDR data also recorded the left engine (N1) was decreasing whereas the right engine N1 remained.
The FDR data recorded that when the aircraft’s altitude was about 10,600 feet the aircraft began turning to the left. The thrust lever position of the left engine continued decreasing while the thrust lever position of the right engine remained.
The Aircraft Maintenance Log (AML) recorded that the aircraft had two Deferred Maintenance Item (DMIs) related to first officer’s Mach/Airspeed Indicator and the autothrottle system which were entered on 25 December 2020 and 4 January 2021 respectively. The first officer’s Mach/Airspeed Indicator was replaced and DMI closed on 4 January 2021. The autothrottle system TOGA switch was cleaned and the DMI was closed on 5 January 2021.
Sadly everything is pointing to a defective autothrottle causing asymmetric thrust in the climb which led to a loss of control.
On 15 Feb 2021 Boeing issued an FOTB on the prevention of aircraft upsets, details here.
On 10 Feb 2021 the preliminary report was issued. Details below.
On 30 Mar 2021 the CVR memory module was recovered about 500 meters off the coast of Pulau Laki (Laki Island) at a depth of 14 meters under 16cm of mud.
On 18 May 2021 the FAA issued AD 2021-08-14 for 737 Classics requiring operators to verify that the flap synchro wire used by the auto-throttle, is securely connected to a safety sensor. A faulty connection could result in the failure of the auto-throttle system to detect the position of the flaps if the engines are operating at different thrust settings due to another malfunction posing a safety risk.
Boeing discovered that the most recent version of the 737 Classic autothrottle computer does not properly account for a possible latent failure of the flap position sensor. This can cause the autothrottle system’s asymmetric cruise thrust monitor to malfunction, creating a thrust imbalance between the aircraft’s two engines.
The FAA said "At this time, the preliminary data of the ongoing accident investigation shows that it is highly unlikely that the accident resulted from the latent failure of the flap synchro wire. However, the FAA has determined that the unsafe condition identified in this AD could exist or develop in Model 737-300, -400, and -500 series airplanes, and that this AD is therefore necessary to address the identified unsafe condition.”
Boeing issued a Multi Operator Message (MOM) on 30 March 2021 to operators directing them to perform electronic checks of the auto-throttle computer to confirm the wire is connected within 250 flight hours. But because of present COVID low utilization rates, the FAA has now insisted on the checks within 250 flight hours or two months from now, whichever occurs first. The FAA is requiring follow-on inspections every 2,000 flight hours after the initial inspection.
*** Updated 23 Nov 2020 ***
The KNKT issued their preliminary report on 10 Feb 2021.
On 9 January 2021, a Boeing 737-500 aircraft, registration PK-CLC, on a scheduled domestic flight, took off from Soekarno-Hatta International Airport, Jakarta, to Supadio International Airport (WIOO), Pontianak, at 0736 UTC (1436 LT).
The flight was cleared by Air Traffic Control (ATC) to depart on a Standard Instrument Departure (SID) ABASA 2D to Flight Level (FL) 290. After taking off from Runway 25R, the autopilot was engaged at altitude of 1,980 feet. The pilots subsequently requested a heading change to 075° to enable them to deviate from weather. ATC responded with clearance for heading 075° and the flight began a turn to the right. ATC then instructed the flight to stop climbing at 11,000 feet due to conflicting departure traffic from Runway 25L.
About 10,600 feet, the aircraft heading started turning to the left. About 10,900 feet, the autopilot disengaged, and the aircraft turned to the left and started its descent.
At 14:40:37 LT, the radar target of the aircraft disappeared on the ATC radar screen. Thereafter, ATC attempted to obtain information of SJY182 aircraft by calling several times, activating and calling on the emergency frequency, and asking other pilots that were flying nearby. All efforts were unsuccessful to get a response from the SJY182 pilot.
About 1455 LT, the Air Traffic Services (ATS) provider reported the occurrence to the Indonesian Search and Rescue Agency (Badan Nasional Pencarian dan Pertolongan/BNPP), and at 1542 LT, declared the uncertainty phase (INCERFA) of SJY182. The distress phase of SJY182 (DESTRESFA) was subsequently declared at 1643 LT.
At the time of issuing this preliminary report, the memory unit of the Cockpit Voice Recorder (CVR) has not been recovered and the search is continuing.
The Komite Nasional Keselamatan Transportasi (KNKT) acknowledged that the safety actions taken by the Directorate General of Civil Aviation (DGCA) and Sriwijaya Air were relevant to improve safety, however there are safety issues remain to be considered. Therefore, the KNKT issued safety recommendations to address the safety issues identified in this report.
This investigation involved the participation of the National Transportation Safety Board (NTSB) of the United States of America as the State of Design and the State of Manufacture, and the Transport Safety Investigation Bureau (TSIB) of Singapore as States providing assistance. Both agencies have appointed their accredited representatives to assist in this investigation in accordance with the provisions in ICAO Annex 13.
The investigation is ongoing. Should further safety issues emerge during the course of the investigation, KNKT will bring the issues to the attention of the relevant parties and issue safety recommendation(s) as required.
Maintenance Log Examination
The Aircraft Maintenance Log (AML) recorded that the aircraft had two Deferred Maintenance Items (DMIs) related to the first officer’s Mach/Airspeed Indicator and the other to autothrottle system. The details were as follows:
DMI number list 07956
DMI number list 07958
The Badan Meteorologi Klimatologi dan Geofisika (BMKG – Bureau of Meteorology, Climatology and Geophysics) provided enhanced infrared satellite images. The enhanced infrared satellite images at 0730 UTC (1430 LT) and 0740 UTC (1440 LT) indicated that the cloud top temperature at the accident site (red circle) was from -34°C to -21°C.
The superimposed ADS-B-based flight profile with radar weather image at 1438 LT provided by the BMKG indicated that the radar intensity level along the flight profile was not more than 25 dBz9, which means that the flight path did not indicate any significant development of clouds.
WIII 090730Z 30006KT 5000 -RA FEW017CB OVC018 25/24 Q1006 NOSIG=
Flight Data Recorder
The aircraft was fitted with a solid-state Flight Data Recorder (FDR) of part number 980-4700-001 and serial number 4355, manufactured by Honeywell.
Cockpit Voice Recorder
The aircraft was fitted with a FA2100 Cockpit Voice Recorder (CVR) of part number 2100-1020-00 and serial number 000286507, manufactured by L3 Technologies.
Wreckage and Impact Information
The search team utilized a Remotely Operated Vehicle (ROV) which was equipped with an under-water camera, a side scan sonar, an Under-water Locator Beacon (ULB) pinger receiver, and a Multi Beam Echo Sounder.
The investigation is ongoing and will continue to focus on, but not limited to the following:
Indonesia's Ministry of Transport has said that the aircraft had departed Soekarno Airport at 14:36L, climbing through 1700 feet the aircraft was cleared to climb to FL290. Departure control subsequently noticed that the aircraft was not on its assigned heading of 075 degrees, but tracking northwesterly and queried the crew about the heading at 14:40L, but received no reply, within second the aircraft disappeared from radar.
Nurcahyo Utomo, an investigator with Indonesia's National Transportation Safety Committee (KNKT) told news agency Reuters that it was possible that the plane broke apart when it hit water, based on debris found so far. "It possibly ruptured when it hit waters because if it had exploded mid-air, the debris would be distributed more widely,"
ADS-B data shows:
The final track of PK-CLC (Planefinder.net)
Sriwijaya Air has a poor safety record. With 5 accidents in 737's recorded since 2008
09 Jan 2021 - 737-500, PK-CLC, 27323/2616, FF 13/5/1994 (age 27 Years), Sriwijaya Air, Jakarta, Indonesia
31 May 2017 - 737-300, PK-CJC, 24025/1556, FF 17/05/1988, Sriwijaya Air, Manokwari, Indonesia
Overran Runway 35 by 30m whilst landing in heavy rain. The preliminary report states that at approx 550 feet, the PIC instructed the SIC to turn on the wiper and reconfirmed to SIC that the runway was in sight. Between altitude 500 feet to 200 feet, the EGPWS aural warnings “Sink Rate” and “Pull Up” sounded. Aircraft written off but no fatalities.
1 Jun 2012, PK-CJV, 737-400, 24689/1883, FF 19 Jun 90, Sriwijaya Air, Pontianak, Indonesia
The aircraft departed the left hand side of the runway after landing in heavy rain. The nose landing gear dug in soft ground and collapsed. WIOO 010530Z 23022KT 0600 FEW009CB BKN007 29/25 Q1008 RMK CB OVER THE FIELD
20 Dec 2011, PK-CKM, 737-300, 28333/2810, FF 5 Aug 96, Sriwijaya Air; Yogyakarta, Indonesia
The Captain (PF) flew an unstable VOR/DME approach to runway 09. After touchdown, PF activated the thrust reversers but the crew did not feel any deceleration. Prior to the end of the runway, PF believed that the aircraft would not be able to stop on the runway and decided to turn the aircraft to the left. The aircraft stopped at 75m from the end of runway 09 and 54m from the left side of the centre line. The nose and right hand main gear collapsed.
27 Aug 2008; PK-CJG, 737-200Adv, 23320/1120, FF 23 May 85, Sriwijaya Air; Jambi, Indonesia:
The airplane had been landing towards northwest in heavy rain and marginal conditions, when the brakes failed. The airplane went about 250 meters past the runway and 3 meters below runway elevation. The right hand wing received damage, both engines and the main landing gear detached. Initial reports state that the flaps were at 15 and the thrust reversers were stowed. Jambi Sultan Taha has a single 2000 x 30m asphalt runway and no ILS. Passengers reported that the captain made an announcement before landing of a possible problem and "not to worry".