On 30 January 2006, an Airbus AIRBUS A-319 (C-FKKR) being operated by Air Canada on a scheduled passenger flight from Las Vegas to Montréal as AC 596 commenced take off in normal night visibility on the shoulder of the runway instead of on the centreline before correcting at speed and completing the take off. ATC were not advised and the debris from three broken runway edge lights was not discovered. The first information aboutf the occurrence was sent to the Operator by ACARS two hours after take off. Minor NLG tyre damage was found after flight.
The Investigation was delegated by the National Transportation Safety Board (USA) (NTSB) to the Canadian Transport Safety Board (TSB). The Operator removed and downloaded the aircraft DFDR and sent the data to the TSB. Relevant CVR data was overwritten.
It was noted that the Captain, who had been PF for the flight, had accumulated approximately 11,000 total flying hours which included about 3000 hours on A320 series aircraft split equally between time as Captain and time as Co-Pilot. The First Officer had accumulated a total of approximately 10,500 total flying hours which included about 1900 hours on the type variant involved.
It was established that the aircraft had been taxied onto departure runway 25R at the full length from taxiway B in accordance with clearance (see diagram below). The green taxiway centreline lights continued past the runway holding point along the curved taxiway centreline across the white runway edge line until they reached the runway centreline. It was noted that the runway did not have centreline lights, just white centreline markings which followed an initial 425 metres of displaced threshold arrows at the beginning. Runway edge lights were white except for those on the displaced threshold section between taxiways B and A2 which were red in the take-off direction. All edge lights except those in the taxiway merge areas were raised. A rolling take off had been made. During the initial stages of the takeoff the pilot was initially unaware of the misalignment because he was "scanning the airspeed and the engine instruments" without also (as also required by SOPs) "observing that the aircraft is on the runway centreline when the thrust levers are advanced and the take-off phase is activated".
After completing this internal scan, the First Officer reported that he "looked outside and saw a red light in front of the aircraft (and) realised that the aircraft was not on the runway centreline". He informed the Captain "who had already started to correct to the left". DFDR data showed that this change of direction "corresponded to a six-degree heading correction and was made approximately 11 seconds into the take-off run at a speed of 64 knots". At the beginning of this corrective action, the aircraft had been approximately 245 metres from the runway threshold, approximately 9 metres to the right of the runway edge lights and approximately 35 metres feet right of the centreline of the 45 metre-wide runway.
During the initial take-off roll, the pilots reported that they had "felt a sensation similar to the aircraft going over pavement joints (which) was considered unremarkable". The aircraft was found to have "regained the runway surface" in the vicinity of the displaced threshold markings, at which point, it had been accelerating through 113 KCAS.
Runway 25R threshold markings - Reproduced from the Official Report
It was noted that continuity of the white runway surface edge line at taxiway intersections was in accordance with the applicable FAA AC150/5340-1 and Volume 1 of ICAO Annex 14 Volume 1 Aerodrome Design and Operations but contrary to Canadian practice which includes introducing breaks in these lines at such intersections. It was also noted that the runway shoulders of the incident runway had been constructed so as to be "capable of supporting an aircraft if it runs off the side of the runway".
It was noted that at night, Denver taxiway and runway lighting was usually kept at 'stage two' intensity out of a possible five stages unless otherwise requested and was at this level at the time of the investigated event. All the green taxi centreline and lead-on lights were found to have been functioning normally and, in the absence of overwritten CVR data, the Investigation was unable to establish why this continuous line of lights onto the centreline "did not catch the flight crew’s attention". It was concluded that there was "no other adjacent lighting conditions that could give the erroneous perception that the right (north) runway edge line and lights could be the runway centreline".
The failure to reject the take off once the misalignment had been recognised and the subsequent failure to promptly inform ATC of the possible presence of FOD on the runway were considered. In respect of the former, the Captain's absolute discretion to reject or continue take off in the event of an abnormal situation occurring at low speed was noted, although the associated requirement that if a "condition or situation that may affect the safety of flight is observed, it will immediately be voiced (and) if a rejected take-off is not required, the Captain will call 'continue' ” which was not reported to have occurred. In respect of the latter, it was considered that it would have been "appropriate" to inform ATC.
It was found that neither of the pilots were frequent users of Denver - it was the Captain's second night departure and the First Officer's first departure from the airport. It was noted that having been instructed by ATC to maintain visual contact with the aircraft departing ahead, this may have had the effect of reducing the attention given by the Captain to ground visual aids whilst aligning the aircraft for take-off. It was considered "likely that the Captain relied on peripheral vision to align the aircraft and may have perceived the white runway side stripe marking, which intersected the taxiway centreline, as the runway centreline marking (which) would explain why the aircraft was initially aligned to the right of the right runway edge lights".
It was noted that there had been three very similar previously documented (but not investigated) events in January/February 2006 during which unidentified aircraft damaged the runway 25R edge lights at night and that there had been another since the event under investigation. These other events were not reported and thus had only been discovered during routine runway/taxiway inspections so that as with the late reporting of the investigated event, prior to debris discovery, other aircraft were at risk of damage.
The formal statement of Causes and Contributory Factors was as follows:
"The Pilot Flying likely relied on peripheral vision to taxi the aircraft because of the requirement to maintain separation with the aircraft departing ahead. This, combined with the aerodrome markings, resulted in the misalignment of the aircraft and the initiation of the take-off from the asphalt runway shoulder instead of the runway centreline."
Three Findings as to Risk were also identified as follows:
(1) A rolling take-off reduces the crew’s time for conducting a thorough outside visual check and verifying runway alignment before initiating the take-off roll.
(2) Taxiways B1 and A2 centrelines curve onto the runway edge line. At night, this could result in pilots aligning their aircraft with the runway side stripe marking instead of with the runway centreline.
(3) This occurrence was reported to company dispatch and air traffic services two hours after the event. During that time, debris left by the broken lights could have posed a hazard for other aircraft using Runway 25R.
Finally it was formally documented as an Other Finding that "the other three similar events that happened on Runway 25R at Las Vegas were not reported (and) failure to declare such events deprives investigators of important data that could help to identify the contributing factors that lead to this type of event".
Safety Action taken by the Las Vegas Airport Authority as a result of the investigated event was noted to have included modifications to taxiway markings at the threshold of runway 25R as follows:
- at taxiway B1, the radius of the taxiway centreline was extended past the runway edge line to meet the runway centreline in the displaced threshold arrow area.
- at taxiway A2, the radius of the taxiway centreline that curves to the runway edge line was erased, and the taxiway centreline now extends to the threshold markings.
However, these actions only had the effect of standardising the taxi lines onto the runway at these two points with the one that was already in place at the taxiway used by the incident aircraft at the time it was misaligned and so were actions not derived directly from the circumstances of the investigated event or directed at the prevention of an identical occurrence.
The Final Report of the Investigation was authorised for release on 1 February 2007 and such action followed. No Safety Recommendations were made.
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