Air transportation safety investigation A21F0210

The occurrence

On 29 November 2021, the Mitsubishi Heavy Industries, Ltd. CL-600-2D24 aircraft (Regional Jet Series 900) (registration C-GJZV, serial number 15424) operated by Jazz Aviation LP was conducting flight JZA767 from San Diego International Airport, California, United States, to Vancouver International Airport, British Columbia, with 2 flight crew members, 2 cabin crew members, and 69 passengers on board. At about 1842 Pacific Standard Time, during the hours of darkness, the aircraft took off to the left of the centreline on Runway 27, and the left main landing gear wheels contacted 3 runway edge lights before the aircraft's trajectory was corrected towards the runway centreline.

While the aircraft climbed, the flight crew detected a fuel imbalance that they were unable to correct, so they shut down the right engine and declared an emergency. The aircraft diverted to Los Angeles International Airport, California, United States, where it landed and stopped on the runway at approximately 1946. Passengers disembarked and were transported to the terminal. None of the passengers or crew members were injured. Emergency personnel reported that 1 of the left main landing gear tires was deflated and that smoke was coming from the wheel. The aircraft’s No. 1 tire sidewall was later found to have been damaged, and the aircraft’s left flap had sustained 2 punctures.

In this occurrence, the misaligned takeoff and the fuel imbalance were 2 separate and unrelated events, and the investigation treated them as such.

To determine the factors that contributed to the aircraft’s misalignment on the runway, the investigation examined the visibility conditions in which the aircraft took off from San Diego International Airport. From pushback to takeoff, the aircraft was operating at night and in fog, in an area where visibility was between ¼ statute mile and ½ statute mile and deteriorating. As a result, there were few visual cues available to the flight crew to identify and verify the aircraft’s position on Runway 27. One of these cues was the portion of the lead-on taxiway centreline marking that was visible in front of the aircraft; however, when taxiing to position on the runway, the captain taxied the aircraft off the taxiway centreline marking in order to increase the runway distance available for takeoff. In doing so, he had even fewer visual cues on which to rely to determine the aircraft’s position on the runway. When the aircraft subsequently turned left to establish the runway heading in preparation for takeoff, the captain perceived the left runway edge marking as the runway centreline. The limited and ambiguous visual cues that were available likely met the captain’s expectations and, as a result, the aircraft was aligned laterally with the left edge, rather than with the centre of the runway.

Runway 27 had a displaced threshold, and the investigation compared the visual environment of a displaced threshold area with that of a runway threshold. It was found that if flight crews line up on runways in the area before the displaced threshold or conduct intersection departures, both under degraded or nighttime visual conditions and without confirming the aircraft's lateral position on the runway, there is an increased risk of runway misalignments or runway side excursions. This is because displaced threshold areas and runway-taxiway intersections do not have runway threshold markings or runway numbers, 2 distinctive features that allow flight crews to define the width—and therefore, the centreline—of the runway.

The nature of operations at the occurrence airport was also considered. San Diego International Airport, one of the busiest single-runway commercial service airports in the world, has a high volume of arrivals and departures that occur in very quick succession, producing a cadence that flight crews must follow. It was found that the complexity of instrument flight rules operations on a single runway surface, with arrivals on one end and departures from the other end, created an environment in which the flight crew perceived a time pressure for the takeoff. As a result, the first officer was completing the line-up checks while the captain taxied to position, and the first officer therefore did not monitor the progress of the taxi. Due to the reduced number and quality of visual cues and the perceived time pressure felt by the first officer, he did not recognize that the aircraft’s nose was aligned with the left edge of the runway when he assumed the role of pilot flying shortly before the take-off roll commenced.

The investigation determined that shortly afterwards, during the take-off roll, the aircraft’s left main landing gear wheels contacted and severed 3 runway edge lights, causing damage to the aircraft’s tires and flaps. However, this contact was not recognized by the flight crew because they perceived the sounds and vibrations as normal contact with the embedded runway centreline lights, and consequently, they continued with the departure. This aspect of the occurrence revealed a particular safety risk to other aircraft. Owing to the fact that the airport is not equipped with a foreign object debris detection system, the debris was not discovered by the airport operator or controllers until several hours after the misaligned takeoff. If foreign object debris on runways is not detected and identified in a timely manner, there is a risk that it will result in aircraft damage during critical phases of flight.

The investigation also examined the causes of the fuel imbalance during the occurrence. It is likely that, during the completion of either the before-takeoff or after-takeoff checklists, the flight crew inadvertently pressed the gravity crossflow push-button switch instead of the co-located crossflow auto override push-button switch. As a result, during the flight, fuel periodically transferred between the aircraft’s wing tanks by gravity when the aircraft was banked left or right, leading to a worsening fuel imbalance condition.

The guidance provided to flight crews by the air operator, Jazz Aviation LP, and the manufacturer, the Mitsubishi Heavy Industries Regional Jet Aviation Group, to address fuel imbalances was found to be unclear and inconsistent. When the wording in a checklist is ambiguous or unclear, or when the wording in an operator’s checklist differs from that in the checklist provided by the manufacturer, a flight crew may, in an effort to correct an abnormal or emergency condition, conduct procedures in ways not intended by the manufacturer, increasing the risk of entering into an undesired aircraft state. With the auto pilot on, the aircraft was unintentionally placed in a sideslip toward the wing tank with the greater quantity of fuel, and this opposite bank was not recognized by the flight crew. As a result, the lateral fuel imbalance was not controlled, and continued to increase. The fuel imbalance, which was unrelated to the damage sustained during the take-off roll, led the crew to declare an emergency and divert to a nearby airport for an emergency landing. Furthermore, the aircraft checklists did not require the flight crew to close the gravity crossflow valve following the attempted Gravity Crossfeed Procedure. As a result, the open valve occasionally made the fuel imbalance worse during the subsequent manoeuvring and was at one point more than 3 times the maximum permissible.

Following the occurrence, Jazz Aviation LP included additional warnings in its airport charts to highlight the risks of departing from within displaced threshold areas. For example, the San Diego International Airport charts now include a departure consideration informing flight crews of the threat of incorrect runway verification in reduced visibility and prescribes additional measures that should be used to verify the runway and the aircraft’s alignment with the centreline. Jazz Aviation LP also issued a company memo regarding departures from displaced threshold areas. In addition, the air operator revised its line-up check procedure as well as its Gravity Crossfeed Procedure, which now contain more guidance on initiating a sideslip.

Media materials

News release