Teddy Robinson
I don't know where that summary came from but it is wrong in several important respects. Instead of re-quoting misinformation we should (and can) quote directly from the report.
1.6.3 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
On 25 December 2020 during preflight check, the engineer found the first officer’s
Mach/Airspeed Indicator malfunctioned. The engineer then transferred the defect
into the DMI list number 07956 due to unavailability of spare part. According to the
Sriwijaya Air Boeing 737 Minimum Equipment List (MEL), the item was classified
as repair category C8.
On 4 January 2021, the first officer’s Mach/Airspeed Indicator was replaced and test
result was satisfied. As such, the DMI number list 07956 was closed.
DMI number list 07958
On 3 January 2021, the pilot reported that autothrottle was unserviceable. The
engineer rectified the problem by cleaning the autothrottle computer’s electrical
connector. After re-installation, the Built-in Test Equipment (BITE) test result was
good.
On 4 January 2021, the pilot reported that autothrottle was unserviceable. The
engineer tried cleaning the autothrottle computer’s electrical connector but the
problem remained and it was transferred to DMI number list 07958.
On 5 January 2021, the engineer rectified the problem as stated in the DMI number
07958 by cleaning autothrottle Takeoff and Go Around (TOGA) switch and
conducted a BITE test on the autothrottle computer. The BITE test result was good
and the DMI was then closed.
There were three attempts to fix the autothrottle.
1.1 History of the Flight
On 9 January 2021, a Boeing 737-500 aircraft, registration PK-CLC, was being
operated by PT. Sriwijaya Air on a scheduled passenger flight from Soekarno-Hatta
International Airport (WIII), Jakarta 1 to Supadio International Airport (WIOO),
Pontianak2. The flight number was SJY182. According to the flight plan filed, the
fuel endurance was 3 hours 50 minutes.
At 0736 UTC (1436 LT3) in daylight conditions, Flight SJY182 departed from
Runway 25R of Jakarta. There were two pilots, four flight attendants, and 56
passengers onboard the aircraft.
At 14:36:46 LT, the SJY182 pilot contacted the Terminal East (TE) controller and
was instructed “SJY182 identified on departure, via SID (Standard Instrument
Departure) unrestricted climb level 290”. The instruction was read back by the pilot.
At 14:36:51 LT, the Flight Data Recorder (FDR) data recorded that the Autopilot
(AP) system engaged at altitude of 1,980 feet.
At 14:38:42 LT, the FDR data recorded that as the aircraft climbed past 8,150 feet,
the thrust lever of the left engine started reducing, while the thrust lever position of
the right engine remained. The FDR data also recorded the left engine N14 was
decreasing whereas the right engine N1 remained.
At 14:38:51 LT, the SJY182 pilot requested to the TE controller for a heading
change to 075 to avoid weather conditions and the TE controller approved the
request.
At 14:39:01 LT, the TE controller instructed SJY182 pilot to stop their climb at
11,000 feet to avoid conflict with another aircraft with the same destination that was
departing from Runway 25L. The instruction was read back by the SJY182 pilot.
At 14:39:47 LT, the FDR data recorded the aircraft’s altitude was about 10,600 feet
with a heading of 046 and continuously decreasing (i.e., the aircraft was turning to
the left). The thrust lever of the left engine continued decreasing. The thrust lever of
the right engine remained.
At 14:39:54 LT, the TE controller instructed SJY182 to climb to an altitude of
13,000 feet, and the instruction was read back by an SJY182 pilot at 14:39:59 LT.
This was the last known recorded radio transmission by the flight.
At 14:40:05 LT, the FDR data recorded the aircraft altitude was about 10,900 feet,
which was the highest altitude recorded in the FDR before the aircraft started its
descent. The AP system then disengaged at that point with a heading of 016, the
pitch angle was about 4.5° nose up, and the aircraft rolled to the left to more than
45°. The thrust lever position of the left engine continued decreasing while the right
engine thrust lever remained.
At 14:40:10 LT, the FDR data recorded the autothrottle (A/T) system disengaged and
the pitch angle was more than 10° nose down. About 20 seconds later the FDR
stopped recording. The last aircraft coordinate recorded was 5°57'56.21" S
106°34'24.86" E
There was one occurrence of thrust lever decreasing, which continued for over a minute without apparent correction.