Singapore B773 at Batam on Oct 25th 2022, landed significantly below required final reserve fuel

Last Update: February 19, 2024 / 15:19:00 GMT/Zulu time

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Photo of Singapore Airlines 9V-SWH, Boeing 777-300 — Singapore Airlines 9V-SWH, Boeing 777-300 (Photo credit: Alec@B92 / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Oct 25, 2022

Classification
Report

Airline
Singapore Airlines

Flight number
SQ-319

Departure
London Heathrow, United Kingdom

Destination
Singapore, Singapore

Aircraft Registration
9V-SWH

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

A Singapore Airlines Boeing 777-300, registration 9V-SWH performing flight SQ-319 from London Heathrow,EN (UK) to Singapore (Singapore) with 280 people on board, had departed London with 106,164 kg of fuel and was descending towards Singapore when Singapore Approach told the crew to expect runway 20R for landing, the flight management computer indicated they would land with 7,000 kg of fuel remaining well above the 3,084 kg of requirement final reserve fuel. 4 minutes later approach instructed the crew to enter a hold due to tailwind for runway 20R. The weather radar on board of the aircraft showed the aerodrome was receiving heavy precipitation, their alternate airports except Batam were also affected by the thunderstorm cell. Another 5 minutes later ATC informed all crews on frequencies that the runways would be switched from 20 to 02, and SQ-319 was assigned runway 02L. The aircraft was subsequently vectors to runway 02L, however about 25 minutes after the crew was assigned runway 20R ATC informed the crew that all landings at Singapore were held off to assess the weather conditions, two aircraft had gone around on approach to runway 02L, there would be another 5 minute delay. The B773 was instructed to enter a hold again. About 31 minutes after being assigned runway 20R the aircraft arrived in that hold, the crew informed ATC they would be able to complete just one hold and then needed to divert. Visibility on runway 02L had further deteriorated. The crew therefore initiated coordination for a potential diversion to Batam (Indonesia). Upon completing the first hold there was still no update on the weather situation, the crew indicated they could do another round, the distances to Singapore and Batam Airfields being about the same from their hold. After completing the second hold the crew was vectored away from both Singapore and Batam, the crew queried that vector and was told, that Singapore was still not able to accept approaches and Batam had not yet approved the diversion. The crew requested to fly an orbit which was approved. The captain became pilot flying, the first officer pilot monitoring. After completing the orbit the crew decided to divert to Batam assessing they would still be able to land with the final reserve fuel remaining. ATC informed the crew that approval for their diversion to Batam was still pending. The crew told ATC they were down to minimum fuel now, the approval for the diversion was still pending. 51 minutes after being assigned runway 20R the crew declared Mayday Fuel at about 13nm southeast of Batam Airport. While on approach to Batam's runway 22 Batam informed the crew there was a tail wind of 14 knots gusting up to 30 knots on runway 22, the captain opted to discontinue the approach and position for runway 04 with the intention to perform an autoland on runway 04. The autopilot appeared to capture both localizer and glideslope, however, descending through about 700 feet AGL "NO AUTOLAND" was annunciated, both localizer and glideslope were showing a full-scale deflection. The autopilot was disconnected and a go around initiated. 67 minutes after receiving information to land on Singapore's runway 20R the aircraft repositioned for another approach to Batam's runway 04. The crew informed ATC that they now needed to land on runway 04 successfully on the next attempt. When the aircraft broke through clouds the aircraft was high on the approach, the captain increased the rate of descent however received a GPWS excessive sink rate warning at 1400 fpm rate of descent. The crew initiated another go around at 212 feet AGL, the crew informed ATC they would now perform a tear drop procedure to visually land on runway 22. The aircraft managed to touch down on runway 22 about 77 minutes after being assigned to Singapore's runway 20R and rolled out without further incident. Singapore's TSIB commented: "The aircraft touched down at Batam Airport at 0919 hrs with fuel remaining significantly below the FRF of 3,024 kg." never mentioning how many kgs of fuel were remaining in the end.

On Feb 19th 2024, 5 months after Singapore's TSIB released their final report, The Aviation Herald received information, that while waiting for the weather to improve at Singapore Aerodrome the crew was able to see Batam Aerodrome in the clear and reset their diversion field to Batam, enabling them to do two more holds at Singapore. At the end of the two holds, with 3.5 tons of fuel remaining, the crew declared Mayday Fuel and diverted to Batam. The crew self positioned the aircraft for a VOR approach to Batam's runway 22, ATC told them there were 14 knots tailwind gusting to 30 knots for runway 22, the crew went around at 1600 feet with 2.8 tons of fuel remaining. The crew positioned for an ILS approach to runway 04 and needed to go around from about 240 feet AGL as they were not able to see the runway, 2.0 tons of fuel were remaining. The crew flew a right downwind to self position for another ILS approach to runway 04, during the approach they received GPWS warnings "SINK RATE" and "PULL UP", the crew went around again from about 300 feet, 1.3 tons of fuel remaining. During the missed approach ATC informed the crew that the weather conditions for runway 22 had improved and the crew positioned for a visual approach to runway 22 and touched down on runway 22 safely with 0.6 tons of fuel on board. The aircraft reached the apron with 0.4 tons of fuel remaining.

In October 2023 Singapore TSIB released their final report concluding the probable causes of the "Low on Final Reserve Fuel" occurrence (no classification like incident, serious incident or accident was provided, too) were:

- The flight crew appeared to have given preference to land at Changi Airport over diverting to Batam Airport where the weather was good.

- The flight crew offered to perform an additional hold and an orbit despite informing SAC that they could only perform a single hold and would be down to minimum fuel.

- The weather over Batam Airport started to deteriorate shortly after the flight crew decided to divert.

- The flight crew did not realise that an autoland should not be performed on Runway 04 of Batam Airport in accordance with the operator’s procedures as information contained in the approach charts indicated that the heading for the final approach course of the localiser signal is 41°, a 1° offset from the runway heading.

- The operator’s Batam Airport briefing document did not indicate that an autoland should not be performed on Runway 04 as the approach charts indicate that the localiser final course is offset from the runway heading even though such information is included in its airport briefing document of other airports.

- The appearance of the “NO AUTOLAND” message on the PFD startled the PF who eventually decided to perform a go-around even though the flight crew were able to sight the Runway 04 as they were descending past 1,195 feet AGL.

- The appearance of the “NO AUTOLAND” message, coupled with a low fuel situation, likely intensified the flight crew’s workload as they did not establish communication with Nadim Tower and did not realise that no landing clearance was given for their first attempt to land on Runway 04.

The TSIB analysed the flight crews' decision making:

The operator has indicated that there is no set policy or procedure for initiating a diversion and provides its flight crew with the discretion to initiate a diversion as required, as they are in the best position to evaluate the dynamic factors of each individual flight.

The operator’s fuel policy is clear in the guidance to its flight crew that if the maximum delay or an EAT is known, the flight may continue to hold, as long as landing at destination is assured and the fuel remaining at touchdown is not less than the FRF. However, the situation faced by the flight crew on the day of occurrence where information on the maximum delay or EAT was not available does not necessarily mean that a diversion should be initiated immediately.

The decision to initiate a diversion when an aerodrome is unable to accept arrivals is not always straightforward. The flight crew would have to balance the possibility of potentially holding a while longer and possibly landing with more than the FRF requirement at the scheduled arrival airport against the possibility of diverting earlier but landing below the FRF requirement at the diversion airport.

In this occurrence, the flight crew appeared to have preferred to land at the scheduled arrival airport, Changi Airport, and held off deciding to divert based on the following decisions that were made:
(a) They offered to perform another hold over SAMKO at 0839 hrs even though Arrival Control was unable to offer any update when queried by the PM earlier at 0836 hrs and they had previously indicated that they could only perform a single hold.
(b) They indicated that they could perform an orbit at 0842 hrs, as they were about to complete the second hold, when informed by Arrival Control that Changi Airport was not accepting any arrivals and was in the midst of coordinating a diversion for the aircraft to Batam Airport.
(c) They queried if Changi Airport was accepting arrivals at 0845 hrs despite declaring that they would divert a minute earlier and had accepted Arrival Control’s instruction to be vectored towards Batam Airport.

With the decision taken to stay in hold as much as possible in hope that the scheduled arrival airport starts to accept arrivals again, the trade-off for any flight crew is the reduced safety margins available to them when the decision to divert is eventually made and should they need to perform more than one landing attempt due to unforeseen events such encountering windshear during short finals that requires a go-around to be performed.

The operator opines that the decision taken by the flight crew to stay in hold as much as possible in the hope that the scheduled arrival airport starts to accept arrivals again does not compromise safety margins. It further opines that had the pertinent information been given to the crew, a more informed decision could have been made to extend the hold or to initiate a diversion. Such pertinent information should be in the form of SAC explicitly stating it was holding off arrival.

The investigation team is of the opinion that the repeated information on Changi Airport being unable to accept arrivals should be interpreted that a landing at the airport was not assured and the flight crew could have made a decision based on this information. Between 0820 - 0844 hrs, three other aircraft were presented with similar information by SAC and were able to make a decision to divert earlier.

In this occurrence, the flight crew had identified Batam Airport as a viable alternate destination with fair weather when Changi Airport, Paya Lebar Air Base and Senai International Airport were all affected by heavy precipitation. Unfortunately, when the flight crew persisted with their decision to hold as long as possible, the weather system affecting Changi Airport started to move in the South Easterly direction towards Batam Airport. Had the flight crew initiated a diversion after the first hold based on their original intention as communicated to Arrival Control, when they were first instructed to hold over SAMKO, it is reasonable to believe that they would have arrived at Batam Airport earlier and would be able to attempt a successful landing on Runway 22 in a better weather condition.

Recent studies identified that one of the effects of climate change is more intense and more frequent storms in many regions exacerbated by extreme rainfall and flooding. This may likely result in pilots operating into areas where the weather conditions exceed the limits to conduct a safe landing or results in loss of capacity of an airport that may impact the regional airspace system.

The effects of climate change are also expected to make the operating environment for pilots more unpredictable. The events in this occurrence suggest that it may be prudent for pilots to interpret operating procedures in a more conservative manner to conclude that landing at a scheduled destination is not assured if the air traffic controllers are not able to provide definitive updates. This will allow pilots to make an earlier decision to divert, with higher safety margins, especially when weather conditions are favourable, to increase the chances of conducting a safe landing at the diversion aerodrome.