Description

On 16 February 2023, a Boeing 737-700 (C-GWCN) being operated by WestJet on a scheduled international passenger flight from Las Vegas to Edmonton as WJA1447, completed its night VMC takeoff aligned with the right hand runway edge lights without either pilot apparently being aware. Minor nosewheel tyre damage found after flight led to both tyres being replaced. The lighting damage went unnoticed until the second day after it had occurred and the airport did not notify the operator until over a week after it had occurred. A gross failure by the Captain to exercise due diligence when taxiing was the only identifiable underlying cause.

Investigation

The NTSB “elected not to investigate” and so the Canadian Transportation Safety Board (TSB) conducted the investigation. The aircraft had flown approximately 80 hours before the operator became aware of the event but by this time relevant data on both the FDR and the CVR had been overwritten. Relevant data from the the aicraft QAR and from ADS-B were still available.

The Captain had a total of 26,000 hours flying experience including 14,712 hours on type. He had been employed as a pilot by the operator for 22 years and was familiar with the airport at Las Vegas. The First Officer had a total of 3,794 hours flying experience including 159 hours on type and was acting as PF for the flight. He had been employed as a pilot by the operator for five months. The two pilots had not previously operated together.

What Happened

The investigated flight was the crew’s second sector of their duty which had commenced with a flight from Winnipeg to Las Vegas with the Captain acting as PF. After a one hour turnround, the Las Vegas-Edmonton flight was going to be operated with the First Officer, who was not only very inexperienced on type but had also never previously been to Las Vegas, as PF. After pushback from Terminal 3 ‘D’ gate the flight was cleared to join taxiway ‘B’, turn left on taxiway ’D’ crossing inactive runway 08L/26R and continuing on taxiway ‘D’ to the full length runway holding point for runway 01R (see the illustration below) . The Captain taxied the aircraft as company procedures did not allow First Officers to do this.

Whilst still taxiing and shortly before receiving takeoff clearance, the Captain asked the First Officer to set the after takeoff departure frequency but as a takeoff clearance was imminent and his checks were not yet complete, the First Officer “suggested that they obtain the departure frequency after takeoff given that they would be staying on the tower frequency for five minutes after takeoff". During this discussion, as the aircraft was approaching holding point clearance limit, the TWR controller issued takeoff clearance but it was missed by both pilots. A subsequent repeat was acknowledged by the First Officer who then asked for, received and read back the departure frequency. 

The taxi route from pushback to departure runway 01R. [Reproduced from the Official Report]

The Captain initially taxied the aircraft along the aircraft taxiway centreline but on reaching the edge of the departure runway at its full length, (it had a displaced threshold for landing traffic which was 150 metres from the beginning of the almost 3000 metre-long runway) he then turned prematurely right onto the (white line) runway edge marking ahead and lined up with it having erroneously identified it as the runway’s centreline. During this turn, the Captain asked the First Officer, who was setting the departure frequency given into the radio pre-select position, carrying out a mandatory pre-takeoff memory checklist and giving the cabin crew PA call ‘seats for takeoff’ to confirm that the Takeoff Checks were being completed.

Then, seeing that the First Officer “was taking longer than he had expected” to complete the Takeoff Checks, the Captain advanced the thrust levers to about 40% N1 and once stabilised then further advanced the thrust towards the required takeoff position. He then stated that he saw that the target N1 “had not been attained and that the TOGA button had not been activated” so he pressed it. By this time, he stated that the First Officer had completed the Takeoff Checks and that “as the aircraft accelerated through 50 knots” he handed him control.

Both pilots subsequently stated that they had “heard sounds and felt vibrations during the takeoff roll, but they thought they were going over embedded runway centreline lights”. The Captain “told the First Officer to move to the left to avoid the vibrations, [but] the aircraft otherwise maintained its alignment". The remainder of the flight was without further event.

The following day, a company maintenance technician noted foreign object damage to the right nosewheel and replaced both tyres before certifying the release to service. Only on the second day after the aircraft had departed Las Vegas did the airport operator discover the damage to runway edge lights on the right hand edge of Runway 01R and they did not then notify WestJet of the damage for a further two days. A total of seven edge lights were found to have sustained significant damage and one other edge light was damaged but reparable. The distance between the first damaged light and the final one was found to be about 820 metres (see the scaled illustration below for the positions of the eight lights involved).

It was noted by the Investigation that all runways at Las Vegas had white runway edge lighting but their centrelines were unlit because “VFR weather conditions are predominant at the airport all year round” and that the absence of runway centreline lighting at Las Vegas was included in the company ‘Route & Aerodrome Qualification document’. 

The location of the 8 edge lights hit. [Reproduced from the Official Report]

QAR data was used to identify actions and outcomes during the initial part of the takeoff roll. Three seconds after aligning with the runway heading (position ‘A’ in the illustration above) and without stopping, the thrust levers were advanced (position ‘B’) and after a further 4½ seconds, TOGA was selected (position ‘C’). Almost half a minute later, the eighth edge light was damaged (position ‘D’) just before rotation occurred (position ‘E’) and the aircraft became airborne at 152 KCAS (position ‘F’). The debris from the damaged lights “was contained and located just outside of the runway edge markings”. However the fact that the airport’s routine runway inspections were conducted only by transits on the runway centreline and only at night meant that this broken light debris had continued to pose an avoidable hazard for other aircraft.

Why It Happened

The primary operational reason for the misaligned takeoff was a lack of diligence on the part of the Captain when lining up despite his familiarity with the airport. The First Officer was at the opposite end of the experience scale and unfamiliar with the airport. His predominantly “head-down” time whilst focusing on tasks inside the cockpit “would have limited his ability to perform outside scans during the taxi” and made it unlikely that he would have been able to pay any attention to environmental cues outside of the flight deck window which might have led him to recognise the Captain’s alignment error.

All the available evidence indicated that the Captain had been influenced by a self-imposed desire not to delay the takeoff based on his general experience during Las Vegas departures that there was a tendency for ATC to be “direct and purposeful to ensure timely movements” of aircraft and his awareness that “two aircraft were moving into position behind them as they made their way past the terminal”. This singular focus appeared to lack any recognition of the risk that his First Officer was being continuously overloaded and the direct and indirect consequences of this situation. Not only were his own actions unmonitored but he was also devoting an undue amount of his time on checking what the First Officer was and was not doing. Despite this, his actions in manoeuvring the aircraft towards and onto the runway without even contemplating a delay led him to go straight into a rolling takeoff in which the PF handover to the First Officer ultimately occurred at the latest possible time for the latter’s type experience. This also occurred in the complete absence of any explicit (as opposed to perceived) ATC pressure to depart. The First Officer confirmed that he had only been able to direct his attention outside the window once control of the aircraft was transferred to him with TOGA thrust already set.

It was noted that the absence of runway centreline lighting at Las Vegas “was available in WestJet’s Route & Aerodrome Qualification document” for discretionary use in departure briefings but it was concluded that given the Captain’s personal familiarity with the airport and the benign prevailing weather conditions, this was unlikely to have been mentioned.

It was also noted that as normal at large US airports “the centreline markings and embedded centreline lights for taxiways that enter onto the runway at (the beginning of) a displaced threshold area continue onto the runway, extending parallel to the arrows that lead to the displaced threshold for at least 60 metres beyond the point of tangency or to the displaced threshold bar, whichever is less”(see the illustration below) yet appeared to have been ignored or inadvertently missed as the Captain lined up. 

The (black-bordered yellow) taxiway centreline lead-on markings and embedded lights ignored during the Captain’s incorrect runway edge line up. [Reproduced from the Official Report]

Although no evidence that it had been relevant was found, it was also noted that there was a minor difference between US and Canadian regulations in respect of runway edge line painting between the beginning of a runway and a displaced landing threshold. Whereas at US airports this line was unbroken, at Canadian airports it was absent wherever a taxiway led onto/off a runway - see the comparative illustration below.

Overall it was considered that the Captain’s misalignment on the lit runway edge (despite the first two lights being red rather than white) instead of on its unlit centreline occurred because the absence of centreline lighting “was not at the forefront of his mind during a period of high workload, divided attention and an increased sense of pressure for a timely departure”.

The difference between Canada and the US in edge line marking at runway access points. [Reproduced from the Official Report]

Whilst the Captain was lining up the aircraft on Runway 01R, it was considered that “his divided attention would have caused his perception of cues outside the flight deck to be guided mainly by ‘top-down’ information processing” which would have created an "expectation of how the situation should have unfolded” rather than a ‘bottom-up’ approach in which attention would have been directed to building on foundation knowledge to inform understanding of a particular situation.

Action taken and intended by the airport involved to improve routine runway inspection procedures and thereby reduce the hazard attributable to broken light debris caused by inadvertent runway take offs at night in the absence of any runway centreline lighting was noted.

More generally, it was noted that four of the seven factors which it was concluded influenced misaligned takeoff occurrences at night identified in an a 2009 Australian Transport Safety Bureau (ATSB) Report were present during the 2023 Las Vegas event.

It was also noted that previous TSB Investigations had included nine other runway edge departures, all at night, one of which (in 2006) had involved an almost identical Airbus A319 departure from Las Vegas in which the incorrect alignment was also not recognised as it happened. It was found that Las Vegas airport did not keep any records of misaligned takeoffs.

The formally documented Findings of the Investigation were documented as follows:

Causes and Contributing Factors 

1. The First Officer’s high workload contributed to his attention being focused primarily on managing tasks within the flight deck as the aircraft was taking position on Runway 01R. As a result, he was unable to provide additional support in visually aligning the aircraft on Runway 01R in the proper position. 
2. Influenced by his perceived time pressure to depart, the Captain’s attention was focused primarily on the First Officer and setting take-off thrust which diverted his attention away from laterally aligning the aircraft on the runway. 
3. When the aircraft was turning right to establish on the runway heading in preparation for takeoff, the Captain perceived the right runway edge marking as the runway centreline and the right runway edge lights as the centreline lights. The limited and ambiguous visual cues that were available likely met the Captain’s expectation that the aircraft was aligned on the runway. As a result, the aircraft was aligned laterally with the right edge of the runway, rather than with its centreline. 
4. Due to the reduced visual cues and the inadequate amount of time to fully process his environment from the moment he assumed control of the aircraft, the First Officer did not recognise that the aircraft was aligned with the right edge of the runway when he took control of the aircraft during the takeoff roll. 
5. The aircraft’s contact with the eight runway edge lights was not recognised by the flight crew because they perceived the sounds and vibrations to be normal contact with the embedded runway centreline lights and consequently continued with the departure.

Risk Factors [Safety deficiencies which were assessed not to have been a factor in this occurrence but could be in future ones]

1. If airport operators incorporate only the minimum marking and lighting required by regulation and do not adopt optional enhanced visual aids where possible, there is an increased risk that pilots will not have a full awareness as to where they are on airport surfaces. 
2. If runway inspections cover only the centre portion of a runway, there is a risk that debris on the edges of the runway will go undetected.

Other Factors [Items which could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.] 

1. The elapsed time between the misaligned takeoff and the discovery, by airport personnel, of the broken runway edge lights, as well as the time taken to report the occurrence to WestJet, resulted in data from both the cockpit voice recorder and the flight data recorder being overwritten. 
2. Until misaligned takeoffs at Las Vegas International Airport are identified and recorded, the full extent of the risk of misaligned takeoffs there will remain unknown.

Safety Action was noted to have been taken as follows:

WestJet 

• Issued a ‘Flight Safety Flash’ memo to its pilots about takeoffs commenced from a position prior to a displaced runway threshold which referred to the investigated event and “informed pilots of the potential to inadvertently line up with the runway edge during night departures from runway areas other than the threshold when at airports with runway and taxiway markings and/or lighting which differ from Canadian regulatory requirements”. This memo also reminded its pilots of the mitigations in place to minimise these threats and “alerted them to ground-based threats specific to Las Vegas Airport" which it identified as:
  • a visually uniform airport landscape
  • complex ground operating environment and possible unfamiliarity 
  • airport and area lights blending
  • high intensity runway operations
  • non-standard (relative to Canadian requirements) taxiways, runway markings and lighting.
• Revised the content of the ‘Departures - Taxi Outbound’ section of the Company Route & Aerodrome Qualification for Las Vegas and relocated this content to the ‘Cautions’ section on the front page with the risk associated with departures from the displaced area of Runway 01R highlighted. The Cautions section of this document was also “updated with an increased focus on taxi and runway line-up threats to assist flight crews and raise their awareness of these threats”. The updated document was tagged with a “NEW” button to attract pilots’ attention.

Las Vegas Airport:

• Responsibility for movement area inspections was allocated to the secondary coordinator rather than the primary coordinator because the former is better able to prioritise movement area inspections with fewer distractions. 
• The specification for a runway inspection has been expanded to require three passes - left side, right side and centre - on each runway. 
• Implementation of a 3-phase plan to address runway and taxiway conspicuity has commenced:
  • Phase 1, now complete, consisted of installing taxiway shoulder markings on the north side of taxiways A and D from the hold bar at each taxiway to the runway edge line of Runway 01R. 
  • Phase 2, planned for completion by 30 April 2024 followed by monitoring for 90 days, consists of movement area marking enhancements as follows:
    • installing taxiway shoulder markings on the south side of taxiways E1, F1, and J from the hold bar at each taxiway to the runway edge line of Runway 19R; 
    • installing runway shoulder markings on Runway 19R from the approach end to approximately the precision approach path indicator (PAPI) lights; 
    • applying bituminous surface coating on the shoulders of runways 01L/19R and 01R/19L to increase contrast between runway and shoulder surfaces (full length);
    • continuing public outreach to inform airport users of local markings and light configurations. 
  • Phase 3, estimated to be completed in the autumn of 2025 will take place in conjunction with the next Runway Incursion Mitigation (RIM) project, and will consist of applying bituminous surface coating on the shoulders of runways 08L/26R and 08R/26L to increase contrast between runway and shoulder surfaces (full length).

The Final Report of the Investigation was authorised for release on 10 April 2024 and officially released on 24 April 2024. No Safety Recommendations were made.

Related Articles

• Runway Misalignment
• Runway Excursion
• Runway Lighting
• Runway Holding Position
• Pilot Workload
• Pilot Flying (PF) and Pilot Monitoring (PM)
• Flight Crew Expectation Bias
• Taxiway Surface Markings and Signs

Further Reading

• Factors influencing misaligned take-off occurrences at night, ATSB Transport Safety Report AR-2009-033, 2010.