TriMG B733 at Singapore on Nov 28th 2020, runway incursion
Last Update: August 31, 2021 / 19:08:12 GMT/Zulu time
The occurrence aircraft was later to perform an approach into Paro that resulted in a viral video, see Incident: TriMG B733 at Paro on Jul 12th 2021, unstabilized approach, bank angle and GPWS warning shortly before touchdown, hard touch down.
On Aug 31st 2021 Singapore's Transport Safety Investigation Bureau (TSIB) released their final report concluding the probable causes of the occurrence rated an incident were:
- The runway incursion was a result of the PF assuming that ATC clearance had been given for TMG019 to enter the runway. The PF did not notice that the red stop bar lights were illuminated, indicating that TMG019 was to stop at the holding point at Taxiway E11.
- The investigation team suspects that the PF and PM might have suffered from some degree of tiredness, considering that they had been on duty for more than 13 hours at the time of the incident.
- The aircraft operator’s flight schedule did not allocate the roles of the PF, PM and AFCM to the flight crew. The flight crew decided among themselves on how to share the PF/PM/AFCM duties for the six sectors of the flight. This resulted in an arrangement whereby Captain 1 and Captain 2 operated three sectors and rest on three sectors, whereas the FO operated five sectors and rested on only one sector.
- The aircraft operator did not include the cross-checking of line-up/take-off clearance in the BTO Checklist as the cross-checking was treated as a memory item. In this incident, the cross-checking for line-up clearance was not carried out by the flight crew.
- There were a number of instances in this incident where the flight crew’s performance in terms of CRM had not been optimal.
- The AFCM was available as a crew resource in the cockpit. However, he was not assigned any duties.
- The State of the Operator’s regulations require the availability of a passenger seat as a condition for the extension of maximum duty time with an AFCM for the execution of the flight. However, there was no passenger seat in TMG019.
- The aircraft operator issued sleeping bags to the flight crew members so that they could rest in them on the galley floor when they were not required to be in the cockpit. However, there was no restraint system for the person resting in such a sleeping bag and there was no evidence that this resting arrangement was acceptable to the State of the Operator.
- In the determination of the maximum duty time, the aircraft operator did not include the number of sectors as a planning parameter. The State of the Operator also did not have a requirement for the aircraft operator to include the number of sectors for short haul flights as a planning parameter when determining the duty time limits.
The TSIB analysed:
Cause of the runway incursion
The aerodrome has a number of safety defences to prevent runway incursion at Taxiway E11:
- Clear indications of the runway holding position (where an aircraft should wait if there is no ATC clearance to enter the runway) in the form of (1) enhanced taxiway centreline marking just before the runway holding position marking, and (2) a pair of guard lights on either side of the runway holding position marking
- Red stop bar lights that will be switched off by the Runway Controller after the clearance to enter the runway is given
- Need for ATC clearance to enter the runway Despite these defences, the PF taxied TMG019 into Runway 02C.
On the part of the PF, he did not notice the red stop bar lights nor the runway guard lights. He did not wait for the PM to announce to him that the BTO Checklist was completed before entering the runway. He did not call for, or wait for the PM to call for, the cross-checking of ATC clearance for entering the runway which was required by the aircraft operator’s operations manual as a memory item.
On the part of the PM, after receiving the Runway Controller’s clearance, he did not communicate clearly to the PF that they had to hold TMG019 at the runway holding point. The PM assumed that the PF knew that there was no clearance to enter the runway. The PM did not expect the PF to taxi TMG019 past the holding point at Taxiway E11 when he had yet to announce the completion of the BTO Checklist. The PM appeared to have been in no rush to complete the checklist as the clearance to enter the runway was not yet given. Had he completed the checklist earlier, he would have been in a position to monitor the PF’s actions and to warn the PF about the runway guard lights as well as the status of the ATC clearance and the red stop bar lights.
The investigation team suspects that the PF and PM might have suffered from some degree of tiredness, considering that they had been on duty for more than 13 hours at the time of the incident and that the PM had had a rest of only about 1 hour 45 minutes during the previous five sectors.
Flight crew rostering
The aircraft operator’s flight schedule did not allocate the roles of the PF, PM and AFCM to the flight crew. The flight crew decided among themselves on how to share the PF/PM/AFCM duties for the six sectors.
This resulted in an arrangement whereby Captain 1 and Captain 2 each operated three sectors and rested on three sectors, whereas the FO operated five sectors and only rested on one sector. This imbalance in rostering also resulted in the FO having had the least rest (only about 1 hour 45 minutes).
It may be desirable for a rostering system to allocate flight duties and rest periods more equitably to ensure that no flight crew member will be overly tired.
Resting arrangement in the aircraft
According to the State of the Operator’s regulations, one of the conditions for the extension of maximum duty time with an AFCM is the availability of a passenger seat for the pilot in the role of AFCM, when not required to be in the cockpit, to rest in. However, there was no passenger seat on TMG019. Instead, sleeping bags were issued by the aircraft operator to the pilots so that they could rest in them on the galley floor.
While some pilots do find that it is more comfortable to rest on the floor than to rest on the observer seat or the two-man seat, the investigation team believes that the practice of resting on the galley floor is not safe as there is no restraint system of any form to mitigate the likelihood of injuries during an air turbulence. The aircraft operator ought to review the appropriateness of its practice of allowing its flight crew to rest in a sleeping bag on the galley floor.
There is no evidence that this resting arrangement was acceptable to the State of the Operator. It would be desirable for the State of the Operator to review the appropriateness of the aircraft operator’s practice of allowing its flight crew to rest in a sleeping bag on the galley floor.
Crew resource management
A good CRM practice is the emphasis of situational awareness among the crew members. It is important that all flight crew members identify and communicate any situation that appears unsafe or out of the ordinary. In this respect, the role of the PM is important in monitoring and cross-checking what the other flight crew member is doing, as well as adhering to recommended callouts to ensure shared crew situational awareness.
There were instances in this incident where the flight crew’s performance in terms of CRM had not been optimal:
- After receiving the Runway Controller’s clearance, the PM did not communicate clearly to the PF that they had to hold TMG019 at the runway holding point at Taxiway E11. The PF, who did not pay attention to the PM’s radio communication with the ATC although he should have been monitoring such radio communication, assumed that there was clearance to enter runway and did not elicit a confirmation from the PM.
- The AFCM was not assigned any duty in the cockpit. Thus, a valuable crew resource went unutilised. Notwithstanding the fact that he was not assigned a duty role, he could have helped monitor the actions of the PF and PM, listen in to the radio communication with the ATC, and intervene as necessary.
- The execution of a checklist requires one pilot to read out the check items in the checklist and the other pilot to perform the items in the checklist. The PF called for the PM to carry out the BTO Checklist but did not wait for him to announce “Checklist completed”. Given that the checklist consisted of only two check items, he should have expected the PM not to take too much time to report “Checklist completed” or should prompt the PM of the status of his checklist execution before crossing the runway holding point at Taxiway E11.
- The PF and PM did not conduct a cross-checking regarding ATC clearance to enter the runway as required by the FCTM.
Standard operating procedures
The aircraft operator adopted the BTO Checklist of the aircraft manufacturer, which consisted of only two check items. The aircraft manufacturer left it to aircraft operators to expand the checklist as necessary. The aircraft operator did not expand the checklist.
The cross-checking on whether clearance had been obtained before entering the runway is a memory item. Relying on memory to initiate an important action is not ideal, as there is a possibility for one’s memory to fail. While there is no evidence that this aspect is a contributing factor to this incident, the investigation team is aware that some other operators have included such memory items in the BTO Checklist. It is desirable that the aircraft operator consider minimising the flight crew’s reliance on memory when it comes to important tasks that they have to carry out.
As regards the role of the AFCM and as mentioned in 2.4.2(b), the AFCM was unutilised as a valuable crew resource in the cockpit. There is scope for the aircraft operator to consider a better utilisation of the AFCM and embody this in its standard operating procedures.
Duty time limitation
The ICAO Document 9966 suggests that the number of sectors in a flight should be taken into consideration when setting the maximum duty time.
There is no evidence that the aircraft operator has considered including the number of sectors to be flown in a flight as a planning parameter when setting the maximum duty time. The State of the Operator apparently also does not require the number of sectors for short haul flights to be considered by the aircraft operator in flight planning.
Given that a flight crew’s workload is usually the highest during take-off and landing and that a multi-sector flight, with the multiple take-offs and landings, would cause a higher level of tiredness for the flight crew, it appears that there is merit in factoring in the number of sectors when setting the maximum duty time.
ATC apprising departing flight crew of the departure sequence
Aircraft traffic was low and the flight crew did not hear any transmissions over the runway frequency after they were transferred from the Ground Controller to the Runway Controller. This may have influenced the PF to believe that TMG019 was the only aircraft operating in the vicinity of the airport. This absence of radio transmissions could lead to a reduced awareness and alertness on the part of the flight crew.
It may be useful if the ATC could provide additional information to make the flight crew of departing aircraft aware of arrival traffic. In this incident, it would have been useful to the flight crew of TMG019 if the Runway Controller had informed them that they were to expect departure after one landing. Such information can help manage the flight crew’s expectation as to their turn for departure and can also be beneficial to the flight crew in terms of situation awareness.
This article is published under license from Avherald.com. © of text by Avherald.com.
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