On 6 March 2009, a Bombardier CRJ 705 being operated by Air Canada Jazz on a daylight scheduled domestic passenger flight from Vancouver BC to Whitehorse landed on runway 31L without clearance and after overflying two snow sweepers operating on the same runway. There was no contact between the aircraft and the vehicles or any abrupt avoidance manoeuvre and none of the 58 aircraft occupants or those in the vehicles were injured.
An Investigation was carried out by the Canadian TSB. It was noted that the Incident had not been reported promptly to the TSB and that the Cockpit Voice Recorder (CVR) had not been secured which had both resulted in the loss of evidence which would have been beneficial to the Investigation.
It was established than after transfer from the Whitehorse sector of Edmonton ACC to Whitehorse TWR, an ILS approach to Runway 31L had been hand-flown by the aircraft commander in IMC using the HUD. On initial contact with destination ATC, which was non-radar, no current position or estimate for arrival was given or requested but TWR had asked for a call at 10nm finals and advised that sweeping was in progress and this call was acknowledged. It was noted that just prior to this, the TWR controller had relieved a colleague in position. No 10 nm report (or a level-passing call requested to be made on Box 2 by the ACC controller at transfer) had been made and the aircraft had landed at Whitehorse approximately nine minutes later.
The Meteorological Terminal Air Report (METAR) issued shortly after the landing reported a vertical visibility of 600 feet, horizontal visibility of 1200 metres in light and drifting snow with an RVR of 1370 metres. The flight crew stated that they had established the required visual reference to the runway at approximately 300 feet aal and about 100 feet above the prescribed DA. Once visual reference was acquired:
“…The First Officer and then the Captain observed the two sweeper trucks operating near the beginning of the portion of the runway located before the displaced threshold. The First Officer reportedly advised the Captain that there were trucks on the runway and, perhaps unassertively, that the flight had not received a landing clearance. Neither pilot observed vehicles in or beyond the normal touchdown zone and neither called for a go-around. The Captain, knowing that the flight had been cleared for an approach, believed the sweeper trucks were holding until the flight landed and elected to continue with the landing which was accomplished without further incident.”
The Investigation noted that the landing threshold for Runway 31L was displaced by 430 metres feet. The two vehicles seen were both towing snow sweepers and were operating in tandem. The Investigation established that they had finished a sweeping run of the full length of the runway in the 13R direction and one truck had reversed direction in the turn area on the displaced threshold whilst the other was beginning to do so when the driver had observed an aircraft on very short final. The aircraft’s altitude over the beginning of runway surface was calculated to be 126 feet agl and the Investigation estimated that the aircraft cleared the trucks by about 110 feet prior to a normal landing in TDZ about 730 metres past the two sweepers.
The Investigation found as follows in respect of Causes and Contributing Factors:
- Communication transfers between Edmonton ACC and Whitehorse tower did not take place in accordance with the Inter Unit Arrangement between the two facilities, resulting in a wide variation in aircraft position at the time of the communication transfer.
- The relieving tower controller did not establish the position of (the incident aircraft) on initial contact. The relieving tower controller assumed that (the incident aircraft) was 45 nm from the airport and this resulted in an inaccurate assessment of the flight time left prior to the aircraft’s arrival.
- Information that (the incident aircraft) would have to hold was not communicated to the relieving tower controller during the position transfer briefing and the flight progress strip did not contain holding information, a fix reference or an airport ETA for (the incident aircraft). This reduced the opportunity for the relieving tower controller to establish accurate initial situational awareness and allowed the 45 mile from airport assumption to persist.
- The mental models of the flight crew and the Whitehorse tower controller were not aligned; the flight crew believed the Whitehorse controller knew their location when tower communication was established and their current position was not requested.
- The First Officer handled all (the incident aircraft) ATC communications following the decision to conduct an HGS approach, and several communication errors subsequently occurred. The pattern of communication errors was consistent with task saturation.
- Whitehorse Tower’s instruction to call 10 miles final became a prospective memory task with no relevant memory reminder cue for the First Officer. As well the significance of the instruction to report 10 miles final as a cue for the relieving tower controller to remove the trucks from the runway and issue the landing clearance was not recognized by the flight crew; thus the call was missed.
- The relieving tower controller relied entirely on the instruction for (the incident aircraft) to report 10 miles final to establish situational awareness prior to the aircraft entering the Whitehorse Control Zone. When the crew of (the incident aircraft) did not comply with the instruction to report 10 miles final the relieving tower controller did not receive the necessary trigger to issue a landing clearance.
- The flight crew’s perception that the approach clearance meant there was no equipment on the runway demonstrated a misunderstanding of the difference between an approach clearance and a landing clearance relative to the status of the active runway.
- The flight crew’s perception was that there were no vehicles or obstructions in the touchdown zone. The Captain, believing that the trucks were holding until the flight landed, elected to land without the flight receiving a landing clearance.
The following Findings as to Risk were also detailed:
- There were differences in how the relieving tower controller, compared to other Whitehorse tower controllers, routinely handled Instrument Flight Rules (IFR) arrivals which created the potential for situational ambiguity between controllers, especially during position transfers.
- A PF’s attention resources may be fully occupied, due to moderate to high perceived workload, when hand-flying an approach using the HGS under IMC, resulting in a significantly reduced capacity to monitor radio communications and provide PNF support.
- To properly assess applicants for pilot positions, operators need access to information on experience and performance that is factual, objective, and (preferably) standardised. Transport Canada pilot records are not available to employers - this may lead to the appointment of pilots to positions for which they are unsuited, thereby compromising safety.
- The crew had no assurance that other maintenance vehicles were not on the runway beyond its field of view. Had there been another vehicle on the unseen portion of the runway, the decision to continue the landing would have exacerbated the risk of collision.
It was also noted that “wide area multilateration and ADS-B technology may be useful tools to enhance tower controller situational awareness of traffic and reduce the risk of collision between arriving aircraft and ground vehicles in non-radar environments”.
The Final Report of the Investigation Aviation Investigation Report A09W0037 was authorised for release on 20 July 2010. No Safety Recommendations were made.