Jetstar Asia A320 at Singapore on Jul 27th 2021, takeoff from unlit runway
Last Update: June 12, 2022 / 20:05:37 GMT/Zulu time
Singapore's TSIB released their final report (erroneously identifying 9V-JSM as occurrence aircraft, which performed a flight to Manila about 10 hours later but didn't move at the occurrence time at all) concluding the probable causes of the takeoff incident were:
- Controllers had to judge the hours of darkness to decide when to switch ON the airfield lighting for night operations. This method is subjective.
- When RWC3 (Runway Controller 3) looked out of the tower windows to check if the runway edge lights and runway centreline lights were ON, it is likely that due to expectation bias, she did not notice that the runway lights were OFF.
- RWC3 also looked at the A-SMGCS display to check if the runway lights were ON. However, the graphical presentation of the A-SMGCS display appeared quite cluttered and she did not discern that the runway lights were OFF.
- It is likely that due to expectation bias, the flight crew presumed that the runway edge lights and runway end lights were ON and thus they proceeded with the take-off, on the grounds that such a runway light configuration met the operator’s SOP requirement for a night take-off.
- The FO did not share with the PIC his thoughts about querying ATC on the absence of the runway centreline lights. This suggests that the crew resource management performance was not optimum.
- During the introduction of a new type of edge lights for Runway 3, the ANSP did not consider whether such runway edge lights could be seen, or could be easily seen, by controllers at CET (Changi East Tower).
- Not all controllers were aware that the ANSP has an in-house hazard reporting system.
The captain (42, ATPL, 12,193 hours total, 11,964 hours on type) was pilot flying, the first officer (50, ATPL, 6,706 hours total, 4,298 hours on type) was pilot monitoring.
The TSIB analysed:
Querying ATC about abnormal runway lighting configuration
According to the flight crew, Runway 3’s edge lights were ON when they were entering the runway and remained ON until shortly after the aircraft had lifted off from the runway. They could not recall whether they looked in the direction of the runway end lights and hence were not sure of the status of the runway end lights. The CCTV footage and record of the airfield lighting system obtained by the investigation team clearly showed that they were mistaken, as Runway 3’s edge lights, centreline lights and end lights had not yet been switched ON by RWC3 at CET at the time of the incident.
The operator’s SOP allows take-off without runway centreline lights, provided that both the runway end lights and runway edge lights are ON. The flight crew did not ensure this condition was satisfied before initiating the take-off roll. 220.127.116.11 The flight crew are based in Singapore and familiar with Changi Airport. Such flight crew are expected to regard it as unusual to see Changi Airport operate with the runway centreline lights OFF at night. Even if the runway light configuration meets the operator’s take-off requirement (i.e. runway edge lights ON and runway end lights ON), it would be prudent for such flight crew to query ATC about the absence of the runway centreline lights.
Crew resource management
The flight crew had noticed that Runway 3’s centreline lights were OFF. According to the FO, he did have the thought to suggest to the PIC to query ATC about the absence of the runway centreline lights, but he put off the idea and waited instead to see what the PIC was going to do. This suggests that the flight crew’s crew resource management performance was not optimum.
The FO indicated to the investigation team that, in hindsight, he should have been more proactive to share his thoughts with and make suggestions to the PIC instead of waiting to see what the PIC was going to do.
Expectation bias on the part of the flight crew and RWC3
The investigation team detected several instances of expectation bias12 in this incident, as follow:
- Runway 3’s end lights were OFF, but the flight crew could not recall whether they looked in the direction of the runway end lights and hence could not be sure whether the runway end lights were ON. During the night trial mentioned in paragraph 1.10, the runway end lights could be clearly seen from Runway 20L’s threshold when they were switched ON. Had the flight crew consciously checked for the status of the runway end lights, they would have noticed that the runway end lights were OFF and this could have prompted them to query ATC regarding the status of the runway lights. The flight crew probably had expected the runway end lights to be ON and thus did not positively look out for it.
- Runway 3’s edge lights were OFF, but the flight crew somehow noted that they were ON. As mentioned in paragraph 1.10.5, it was unlikely that Runway 3’s edge lights could appear ON when they were in fact OFF, and also unlikely that other lights could be misidentified or mistaken as the runway edge lights. However, given the numerous taxiway edge lights around the threshold of Runway 20L, the flight crew may have experienced confirmation bias in perceiving the taxiway edge lights as runway edge lights while turning onto the runway, even though they are of different colours. The flight crew did not positively check for the status of the runway edge lights.
- Runway 3’s edge lights and centreline lights are bi-directional. When switched ON, it is doubtful if controllers can see the runway edge lights and runway centreline lights within about 500m along the runway on either side of CET (see Figure 5). While the edge lights beyond this section of the runway might be seen by controllers at CET, they are not easily discernible. When switched OFF, none of these lights could of course be seen. However, RWC3 did not detect anything unusual when she looked out of the tower windows to check the runway edge lights and runway centreline lights13. RWC3 probably had expected the runway lights to be ON and the quick glance at the A-SMGCS could not clearly indicate the status of these lights. Given the bi-directional nature of Runway 3’s edge lights and runway centreline lights, the view of the centre portion of Runway 3 is similar at night whether the runway lights are ON or not. As CET had just been in operation for a few months, controllers might not have realised this similarity. It is desirable that the ANSP highlights such similarity to controllers and develops methods to enable controllers to positively identify the status of the runway lights.
Because of expectation bias, opportunities for the flight crew and RWC3 to notice the unusual configuration of the runway lights were missed. To mitigate the effect of expectation bias, it cannot be overemphasised that operational personnel should be vigilant and make conscious efforts to positively check things out when performing their tasks.
Runway lighting control
SOP for switching ON runway lights for night operations
Runway lights are required to be ON during hours of darkness. At the time of the incident, controllers had to make a judgment as to when to switch ON the runway lights.
The investigation team finds that controllers’ judgment of the hours of darkness could be very subjective for deciding when to switch ON the airfield lighting for night operations. This can result in the airfield lighting in different areas of responsibility being switched ON at different times of the day.
A more objective approach to controlling the airfield lighting for night operations should be considered. For example, an alert (aural and/or visual) could be set to remind controllers to switch ON the airfield lighting at a pre-determined time at or near sunset time.
A-SMGCS display of ON/OFF status of runway lights
According to the ANSP, the A-SMGCS provides controllers with an accurate representation of the ON/OFF status of runway lights. However, the investigation team found that the graphical presentation of the A-SMGCS appeared quite cluttered and that it was not easy to discern whether the runway lights are ON or OFF just by a quick glance at the A-SMGCS display. It seems desirable for the graphical presentation of the ON/OFF status of the runway lights to be enhanced.
Risk assessment on the use of Runway’s 3 edge lights
Although Runway 3’s lighting system complied with international standards, the risk assessment of the runway lighting system apparently did not consider the differences in the views of Runway 3’s edge lights and of the edge lights installed along Runway 1 and Runway 2. As a result, the risk assessment did not consider whether the Runway 3’s edge lights could be seen, or could be easily seen, by controllers at CET, and nor establishing a method for controllers to visually verify the status of the runway lights.
In-house hazard reporting system of the ANSP
The ANSP has a hazard reporting system for controllers to report hazards. However, apparently not all its controllers were aware of this system.
While the ANSP promotes systematically its hazard reporting system to controllers, it appeared that the promotional effort had not been effective in making all its controllers aware of the hazard reporting system.
This article is published under license from Avherald.com. © of text by Avherald.com.
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