Boeing 737-400

On 20 March 2021, a Boeing 737-400F, registered PK-YSF, was being operated by Trigana Air Service on a non-schedule cargo flight from Halim Perdanakusuma International Airport (WIHH), Jakarta, Indonesia with intended destination of Sultan Hasanuddin International Airport (WAAA), South Sulawesi, Indonesia. On board in this flight was two pilots, one engineer and one Flight Operation Officer (FOO). According to the weight and balance sheet, the flight carried 16,672 kgs of general cargo, takeoff fuel of 11,100 kg and the takeoff weight was 60,695 kg (133,835 lbs). The Pilot in Command (PIC) acted as Pilot Flying (PF) and the Second in Command (SIC) acted as Pilot Monitoring (PM). At 0328 UTC (1028 LT), the PM requested clearance to Halim Tower controller (the controller) to pushback and start the engines. At 1031 LT, the PM requested to the controller for taxi clearance. There was no report of aircraft system abnormality prior to the aircraft departure. At 1047 LT, the controller issued clearance to the PK-YSF pilot to enter and to backtrack Runway 24. At 1051 LT, the PM reported ready for departure to the controller. The controller issued takeoff clearance with additional departure clearance that after takeoff, turn left to heading 180° and initially climb to altitude of 3,000 feet. The PM acknowledged the clearance. The takeoff was conducted with reduced takeoff thrust by assumed temperature of 40°C and the aircraft became airborne at 10:52:57 LT. At 1055 LT, the controller advised the pilot to report when established on heading 180°. The PM reported that they were experiencing right engine failure and requested to fly to AL NDB . The controller advised the PM to turn left heading 060° and to climb to 2,500 feet. Furthermore, the controller asked the pilot intention whether to hold over AL NDB or direct for landing approach. The PM replied that they would hold over AL NDB and added the information that no fire was detected. The controller issued clearance to fly to AL NDB at altitude of 2,500 feet. The controller assumed that PK-YSF would return to Halim and advised the Airport Rescue and Fire-Fighting (ARFF) personnel that PK-YSF experienced right engine failure and would return to Halim. At 1058 LT, the controller requested the information of time required for holding over AL NDB and was replied by the PM that holding would require about 15 minutes. Furthermore, the controller requested whether the pilot able to hold at a point about 15 to 20 Nm from AL NDB and was replied by the PM that they did not objection to the proposal. The controller instructed the pilot to maintain outbound heading up to 15 Nm, at altitude of 2,500 feet. This was intended by the controller to manage the departure and arrival aircraft to and from Halim. At 1116 LT, the PM reported that they were ready to turn left for approach. The controller advised the pilot to turn left and to intercept localizer of the Instrument Landing System (ILS) Runway 24. At 1125 LT, the PM reported to the controller that the Runway was in sight. The controller advised that the wind was from 060° at velocity of 6 knots, QNH 1,007 mbs and issued landing clearance. The aircraft touched down on the touchdown zone and shortly after, both wheels of the right main landing gear detached. The controller noticed spark appeared from the aircraft and pressed the crash bell. At 1127 LT, the controller informed pilots of the other aircraft that the runway blocked by the landing aircraft and identified fire on one of the engines. Few seconds later, the PM called the controller whether any fire and was replied by the controller that fire was visible on the left side of the aircraft.

The crew were scheduled to operate two cargo flights from Exeter Airport (EXT), Devon, to East Midlands Airport (EMA), Leicestershire, and return. The co-pilot was the PF for both sectors, and it was night. The sector from EXT to EMA was uneventful with the crew electing to landed with FLAP 40. The subsequent takeoff and climb from EMA to EXT proceeded without event. During the cruise the crew independently calculated the landing performance, using the aircraft manufacturer’s software, on their portable electronic devices. Runway 26 was forecast to be wet, so they planned to use FLAP 40 for the landing on Runway 26, with AUTOBRAKE 3. With both pilots being familiar with EXT the PF conducted a short brief of the pertinent points for the approach. However, while they did mention that the ILS had a 3.5° glideslope (GS), they did not mention that the stabilized approach criteria differed from that on a 3° GS. From the ATIS they noted that the weather seemed to be better than forecast and the surface wind was from 230° at 11 kt. The ATC provided the flight crew with radar vectors from ATC to the ILS on Runway 26 at EXT. The landing gear was lowered and FLAP 25 selected before the aircraft intercepted the GS. FLAP 40 (the landing flap) was selected on the GS just below 2,000 ft amsl. With a calculated VREF of 134 kt and a surface wind of 10 kt the PF planned to fly the approach with a VAPP of 140 kt. At about 10 nm finals, upon looking at the flight management computer, the PM noticed there was a 30 kt headwind, so a VAPP of 144 kt was selected on the Mode Control Panel (MCP). The crew became visual with the runway at about 1,000 ft aal. The PF then disconnected the Auto Pilot and Auto Throttle; the Flight Directors remained on. As the wind was now starting to decrease, the VAPP was then reduced from 142 to 140 kt at about 600 ft aal. As the wind reduced, towards the 10 kt surface wind, the PF made small adjustments to the power to maintain the IAS at or close to VAPP. At 500 ft radio altimeter (RA) the approach was declared stable by the crew, as per their standard operating procedures. At this point the aircraft had a pitch attitude of 2.5° nose down, the IAS was 143 kt, the rate of descent (ROD) was about 860 ft/min, the engines were operating at about 68% N1 and the aircraft was 0.4 dots above the GS. However, the ROD was increasing and soon thereafter was in excess of 1,150 ft/min. This was reduced to about 300 ft/min but soon increased again. At 320 ft RA, the aircraft went below the GS for about 8 seconds and, with a ROD of 1,700 ft/min, a “SINK RATE” GPWS alert was enunciated. The PF acknowledged this and corrected the flightpath to bring the aircraft back to the GS before stabilizing slightly above the GS; the PM called this deviation too. As the PF was correcting back to the GS the PM did not feel there was a need to take control. During this period the maximum recorded deviation was ¾ of a dot below the GS. At about 150 ft RA, with a ROD of 1,300 ft/min, there was a further “SINK RATE” GPWS alert, to which the PM said, “WATCH THAT SINK RATE”, followed by another “SINK RATE” alert, which the PF responded by saying “AND BACK…”. The commander recalled that as the aircraft crossed the threshold, at about 100 ft, the PF retarded the throttles, pitched the aircraft nose down, from about 5° nose up to 4° nose down, and then applied some power in the last few feet. During these final moments before the landing, there was another “SINK RATE” alert. The result was a hard landing. A “PULL UP” warning was also triggered by the GPWS, but it was not audible on the CVR. The last surface wind transmitted by ATC, just before the landing, was from 230° at 10 kt. During the rollout the commander took control, selected the thrust reversers and slowed down to taxi speed. After the aircraft had vacated the runway at Taxiway Bravo it became apparent the aircraft was listing to the left. During the After Landing checks the co-pilot tried to select FLAPS UP, but they would not move. There was then a HYDRAULIC LP caution. As there was still brake accumulator pressure the crew were content to taxi the aircraft slowly the short distance onto Stand 10. Once on stand the listing became more obvious. It was then that the crew realized there was something “seriously wrong” with the aircraft. After they had shut the aircraft down, the flight crew requested that the wheels were chocked, and the aircraft be connected to ground power before going outside to inspect the aircraft. Once outside a hydraulic leak was found and the airport RFFS, who were present to unload the aircraft, were informed.