Rejected Take-Off at Hamilton Airport Involves Kelowna Flightcraft Boeing 727

Incident Overview and Aircraft Details On the night of the occurrence, Kelowna Flightcraft Air Charter Ltd. operated flight KFA273, a Boeing 727-281 with registration C-GKFJ and serial number 21455, from Hamilton Airport in Ontario. The aircraft was scheduled to depart for Winnipeg–James Armstrong Richardson International Airport in Manitoba. At 0208 Eastern Daylight Time, during darkness, the aircraft began its take-off roll on Runway 30. Two snow sweepers were working near the departure end of the runway. Air traffic control instructed the aircraft to abort the take-off, and the flight crew rejected the take-off. The aircraft stopped at approximately the halfway point of the 10,006-foot runway, about 1,200 feet from the snow sweepers. There was no damage and no injuries. ## Operational Context Hamilton Airport serves as the main base for Purolator air cargo operations, operated by Kelowna Flightcraft Air Charter Ltd. The airline conducts several scheduled cargo flights from the airport, typically departing between 0115 and 0140 each morning. Air traffic services at Hamilton Airport are provided by NAV CANADA through a local control tower and the Toronto Area Control Centre. Instrument flight rules clearances are relayed from the Toronto Area Control Centre, and departure clearances must be validated by the centre before departure. This validation is normally accomplished through verbal communication over the interphone between the tower controller and the area control centre controller. ## Control Tower Events At the time of the occurrence, the control tower was staffed by two controllers, but one was on break and not in the tower cab. The controller on duty was responsible for both airport and ground positions, which was normal procedure at that time of night. The radios were configured so that ground and air frequencies were coupled, allowing broadcasts on either frequency to be heard on both. About 45 minutes before the occurrence, the controller cleared two snow sweepers to work on Runway 30 for snow and ice removal. The sweepers were instructed to vacate the runway to accommodate a departure at 0156 and were re-cleared onto the runway at 0200. In the 20 minutes before the occurrence, the controller was busy, making or receiving an average of seven transmissions per minute. Several communications were lengthy, including instrument flight rules clearances, runway surface condition reports, and complex taxi instructions. While communicating with the area control centre, the controller mistakenly requested a flight release for KFA275 instead of KFA273. The error was corrected in subsequent communications. The controller used an extended computer display system, a computer-based coordination system that allows controllers to manage electronic flight data on display screens instead of paper flight progress strips. The system includes a visual reminder called a blocked-runway indicator, which the controller had activated to show that the runway was occupied. ## Contributing Factors The investigation determined that all individuals involved were adequately qualified, trained, and licensed. All vehicles and equipment were operating as designed, and mechanical failures were not considered a factor. The analysis therefore focused on why the controller issued the take-off clearance, why the aircraft began the take-off roll, and why the instruction to abort was initially unrecognized. The controller’s work schedule for the 70 days before the occurrence was a counter-clockwise rotation, meaning progressively earlier start times as shift times changed. Counter-clockwise schedules can contribute to fatigue because they require individuals to sleep at earlier times, which can be more difficult, and they often provide short recovery times between shifts. The scheduling practices at Hamilton Tower typically resulted in the controller transitioning from an early morning shift to a midnight shift, with only 10 hours off duty between shifts. A fatigue avoidance scheduling analysis predicted significant performance decrements, particularly during the first midnight shift. The controller occasionally had difficulty getting adequate sleep during this type of rotation and reported feeling fatigued at the time of the occurrence, which coincided with a circadian trough. The controller had slept for 8 hours in the preceding 24 hours and 16 hours in the preceding 48 hours. Because recent sleep should have lessened the effects of acute or chronic fatigue, and because the previous sleep history was uncertain, the existence of fatigue at the time of the occurrence could not be concluded, although the controller reported feeling fatigued. On the night of the occurrence, the two controllers on duty had agreed that the occurrence controller would work the combined air–ground position from the beginning of the shift at 2345 until approximately 0230, meaning the controller would be in position for close to three hours before being relieved. In the 20 minutes before the occurrence, workload increased as four aircraft taxied for departure. Although the second controller was available for immediate recall, the occurrence controller did not assess the workload as being busy enough to request assistance. This period of increased workload and complexity occurred after the controller had been in position for over two hours and coincided with a circadian low. The practice of working the combined air–ground position at night for extended periods to provide lengthy controller breaks increases the risk of controller errors. ## Sequence of the Clearance Error The controller made a call sign error, possibly due to workload and fatigue, when requesting validation for the departure of KFA273. The two aircraft call signs confused were both for aircraft destined for Winnipeg and scheduled to depart 20 minutes apart. This similarity was a nightly occurrence, which desensitized controllers and pilots to its potential impact and reduced the effectiveness of defences in place to address it. While viewing the extended computer display system, which needed to be manipulated during the validation request, the blocked-runway indicators located directly below the aircraft’s strip went unnoticed. The controller caught the call sign error while beginning a transmission to KFA273, informed the aircraft to stand by, and then corrected the error with the area control centre. The controller then issued a take-off clearance to KFA273. Possibly distracted by the need to make the previous correction, the controller again did not detect the blocked-runway indicator during the routine scan. The practice of authorizing aircraft to arrive or depart on a runway for which a blocked-runway indicator is showing indicates desensitization to the importance of the indicator, eliminating its effectiveness as a defence and increasing the risk of aircraft being authorized to use an unavailable runway. As the controller was completing the clearance, a visual scan of the runway surface detected the vehicles, and the controller paused and informed the aircraft to stand by. The required phraseology from the Air Traffic Control Manual of Operations to cancel the take-off clearance was not used. It could not be determined whether using correct phraseology would have altered the outcome. The controller paused after the words “cleared take-off Runway 30” were spoken. After this brief pause and without releasing the push-to-talk button, the controller stated “actually standby” rather than the required phraseology, “Take-off clearance cancelled.” During the pause, the pilot not flying on KFA273 assumed the transmission was complete, depressed the aircraft’s push-to-talk button, and read back the clearance. When the controller eventually released the tower push-to-talk button, only the tail end of the transmission, which included the aircraft’s call sign, was heard. Because call signs alone are often used to acknowledge receipt of a transmission, the controller assumed the aircraft understood the instruction to stand by and did not expect it to take off. The flight crew, having not heard the portion of the transmission informing them to stand by, assumed everything was normal and began their take-off procedure. ## Take-Off Roll and Rejection The controller then instructed the vehicles to exit the runway, briefly glanced at KFA273 to confirm the aircraft was not rolling, and then focused on the Purolator Apron to issue taxi instructions to another Flightcraft aircraft. During this time, KFA273 began the take-off roll outside the direct field of view of the controller. Immediately after the controller finished the taxi instructions, attention returned to Runway 30, and the movement of KFA273 was noticed. The controller immediately instructed KFA273 to abort the take-off. At the time of the abort instruction, KFA273 had just reached 80 knots. The pilot not flying announced the speed, and the pilot flying confirmed. At the same time, a chart on the pilot flying’s pedestal fell and briefly distracted the crew. Apart from the brief distraction, the crew considered the take-off to be proceeding normally, as expected, and their forward view of the runway ahead presented no indication otherwise. That which is expected is a central factor that drives attention behavior, and cues indicating that the situation is not as expected may not attract attention away from anticipated tasks. Situations can appear normal or familiar unless something out of the ordinary is of sufficient magnitude to attract attention and subsequent analysis. The cockpit environment was relatively noisy. The abort call was simultaneous with other sensory input, unexpected due to its rarity, and without supporting cues such as a visual sighting of the obstacle. As a result, it was not sufficiently compelling to alter the crew’s mental model of the situation or their expectation of an uneventful take-off, and it initially went unnoticed. As the aircraft began to crest the middle section of the runway, the crew began to notice unusual lights, and the pilot not flying then recognized that the abort take-off call, issued 9 seconds earlier, had been intended for them. The crew rejected the take-off and brought the aircraft to a stop at a safe distance from the vehicles.