Porter DH8D and Jazz DH8D at Sudbury on Oct 14th 2016, near collision
Last Update: January 24, 2018 / 16:47:38 GMT/Zulu time
A Jazz de Havilland Dash 8-400, registration C-GXJZ performing flight QK-8604 from Sudbury,ON to Toronto,ON (Canada), departed Sudbury's runway 22 on a visual departure and was intending to pick up IFR clearance once airborne. Climbing through 4000 feet about 8nm south of Sudbury the crew received a TCAS resolution advisory, the Porter Dash 8 also received a TCAS resolution advisory, both crews complied with their TCAS resolution advisories.
Once clear of conflict both aircraft continued to their destinations for safe landings.
The Canadian TSB reported according to radar data the separation between the two aircraft reduced to 0 feet vertical and 0.4nm horizontal involving a risk of collision, an investigation has been opened into the occurrence.
On Jan 23rd 2018 the TSB released their final report concluding the probable causes of the serious incident were:
Findings as to causes and contributing factors
- The North Bay controllers’ practice of clearing instrument flight rules (IFR) aircraft for an approach without regard to the active runway at Sudbury Airport, Ontario, created a situation wherein arriving IFR traffic was counter to the flow of, and therefore more likely to come into conflict with, visual flight rules traffic operating at the airport.
- The Sudbury flight service specialist’s initial taxi departure advisory to Jazz Aviation LP flight 604 (JZA604) did not include information regarding inbound opposite-direction IFR traffic. As a result, the JZA604 flight crew was not fully aware of the traffic situation when it taxied to position on Runway 22.
- The North Bay controller approved the visual flight rules departure of JZA604 without a coordinated plan to prevent a conflict between the aircraft and opposite-direction traffic.
- The visual-approach clearance issued by the North Bay controller and accepted by the Porter Airlines Inc. flight 533 (POE533) flight crew while the aircraft was in instrument meteorological conditions likely led to an expectation by the controller that JZA604 and POE533 would be able to see and avoid each other.
- JZA604’s left turn was not apparent on the North Bay controller’s Canadian Automated Air Traffic System situation display because the display was operating on a scale of 250 nautical miles.
- The North Bay controller was unaware that JZA604 was east of the Runway 04 extended centreline, and suggested that the aircraft turn 30° right, essentially bringing it back toward the approach path for Runway 04.
- Jazz Aviation LP did not have standard operating procedures for the selection of the traffic alert and collision avoidance system (TCAS) continuous and automatic modes. During the occurrence, the captain’s traffic display was still in default automatic mode and, as a result, the captain did not have a complete understanding of POE533’s position and altitude.
- Following the TCAS resolution advisory (RA), the JZA604 captain manoeuvred the aircraft contrary to the RA instructions. Although permitted by company standard operating procedures, this alternate manoeuvre reduced the vertical separation between the 2 aircraft.
- The Porter Airlines Inc. TCAS simulator training syllabus and scripts do not address RA commands other than climb and descend and their associated reversals. As a result, the captain of POE533 was likely inexperienced in the initial RA instruction to maintain vertical speed, and manoeuvred contrary to the command, which reduced the vertical separation between the 2 aircraft.
Findings as to risk
- If flight crews do not report to air traffic control that manoeuvres are being executed as a result of a TCAS RA, controllers may be uncertain about an aircraft’s intentions and issue contradictory instructions, increasing the risk of collision.
- If guidance provided to flight crews by operators includes phraseology that is not consistent with international best practices, ambiguous information regarding aircraft manoeuvring may be reported to air traffic control, increasing the risk of collision.
- If reporting of occurrences to the TSB is delayed, there is a risk that the cockpit voice data necessary to identify and communicate safety deficiencies will be unavailable.
The TSB described the sequence of events:
At 0959:30, when JZA604 became airborne, POE533 was approximately 17.3 nm south of the airport, proceeding directly to the PEKVU initial approach waypoint and descending through 6700 feet.
Ten seconds later, while still in IMC, POE533’s flight crew requested further clearance from the North Bay controller, and the controller cleared them for a visual approach to Runway 04. After the crew acknowledged the clearance, the North Bay controller informed them that JZA604 was conducting a VFR departure from Runway 22 and would be instructed to turn to the west, and that MAL8056, which was 10 nm south of the airport, was also inbound to land on Runway 04.
At 1000:55, the North Bay controller contacted JZA604, and its flight crew advised the controller that they were levelling off at 4000 feet and were approximately 5 nm south of the airport. At that time, POE533 was approximately 14 nm south of the airport and descending through 5800 feet.
At 1001, JZA604 turned left (east), 20° from the runway extended centreline, which was also the approach path for Runway 04 (Figure 2). The North Bay controller had not been informed of this turn or noticed it on the radar, and subsequently suggested12 that JZA604 turn 30° to the right (west). The controller then informed JZA604 of POE533’s position. The JZA604 crew responded to the suggestion to turn by stating that they would complete the turn shortly, but were delaying briefly due to some rain showers to the west.
At 1001:15, JZA604, which was approximately 6.1 nm south of the airport in level flight at 4000 feet, began a turn to the west. POE533 was approximately 12.6 nm south of the airport at this time, descending through 5200 feet.
At 1001:34, the North Bay controller informed the POE533 crew that JZA604 was now at their 1 o’clock position,13 flying straight out from Runway 22 at 4000 feet under VFR, and turning to the west.
At 1002:02, the North Bay controller informed POE533 a second time of JZA604’s position. JZA604 was still at POE533’s 1 o’clock position, 5 miles ahead and flying toward POE533 at 4000 feet. POE533 was approximately 11.5 nm south of the airport and descending through 4800 feet, while JZA604 was approximately 7.5 nm south of the airport.
At 1002:10, the North Bay controller strongly suggested to JZA604’s crew that they turn further to the west and informed them that POE533 was at their 12 o’clock position, descending through 4700 feet, 3 miles ahead of them and flying toward them. The JZA604 crew began a 23° bank turn to the right and informed the controller that they were turning west.
At 1002:11, both POE533 and JZA604 received a traffic alert (TA) from their respective traffic alert and collision avoidance systems (TCASs). The separation between the 2 aircraft was 570 feet vertically and 2.7 nm horizontally, with a closure rate of 330 knots.
At 1002:21, both POE533 and JZA604 received a resolution advisory (RA) from their respective TCASs. The separation between the 2 aircraft was 336 feet vertically and 1.7 nm horizontally.
The TSB analysed that the event occurred shortly after a controller change at North Bay. The incoming controller was not briefed that runway 22 was the active runway at Sudbury and thus remained unaware of possible departures on runway 22. In addition, the incoming controller assumed that the departing Jazz DH8D would immediately clear the extended runway center line after becoming airborne for the visual departure, however, did not communicate this expectation to Sudbury. In addition, the incoming controller cleared the arriving Porter for a visual approach when, unknown to the controller, the aircraft was still in instrument meteorogic conditions. The TSB wrote: "Following that request, the incoming North Bay controller cleared POE533 for a visual approach to Runway 04 without confirmation that the flight crew had the airport in sight. This decision was likely based on the fact that, during the transfer of position responsibility briefing that took place moments before, the controller had been informed that visual approaches could be conducted once aircraft were below 5000 feet. The visual-approach clearance issued by the North Bay controller and accepted by the POE533 flight crew while the aircraft was in IMC likely led to an expectation by the controller that JZA604 and POE533 would be able to see and avoid each other."
The TSB analysed with respect to evasive maneouver different to TCAS RA conducted by the Jazz DH8D:
Although JZA604 was operating under VFR and had not yet been authorized to enter IMC, manoeuvring contrary to an air traffic control (ATC) instruction or clearance is permitted under Canadian Aviation Regulations (CARs) subsection 602.31(3) when its purpose is to comply with a TCAS RA. At approximately the same time that the RA instruction to climb was received, the captain of JZA604 made visual contact with POE533. Given that JZA604 would likely have encountered IMC if a climb had been executed, the captain believed that turning would be the most appropriate evasive manoeuvre.
The captain’s decision to deviate from the advisory was permitted by Jazz Aviation LP SOPs, which allow visual manoeuvring contrary to an RA instruction if a flight crew perceives information that they believe to be more accurate, such as by having the aircraft in sight.
As a result of these factors, the JZA604 captain manoeuvred the aircraft contrary to the RA instructions. Although permitted by company SOPs, this alternate manoeuvre reduced the vertical separation between the 2 aircraft.
Jazz Aviation LP TCAS simulator training scripts are not specific to the types of RA commands that flight crews receive during simulator training. As a result, flight crews may be inexperienced in some of the less common RAs, and may manoeuvre contrary to an RA or have a delayed reaction.
With respect to the Porter crew not complying with their TCAS RA instruction the TSB analysed:
Following the TCAS RA to “maintain vertical speed, crossing, maintain,” the immediate reaction of POE533’s flight crew was to reduce their rate of descent. That response resulted in a subsequent RA to descend, with which the crew complied. The intent of the initial advisory was that the crew should continue descending at the current rate.
The Porter Airlines Inc. TCAS simulator training syllabus and scripts do not address RA commands other than climb and descend and their associated reversals. As a result, the captain of POE533 was likely inexperienced in the initial RA instruction to maintain vertical speed, and manoeuvred contrary to the command, which reduced the vertical separation between the 2 aircraft.
The TSB analysed with respect to communication following the TCAS RAs:
Neither of the 2 flight crews used the required phraseology to clearly communicate to ATC that they were responding to a TCAS RA. Instead, both flight crews reported only the evasive manoeuvres they were taking: the crew of JZA604 reported that they were climbing, and the POE533 crew reported that they were turning. According to the SOPs of both airlines, the correct phraseology was “(call sign), TCAS climb (or descent).” Consequently, ATC personnel were unaware that a TCAS RA event had occurred. If flight crews do not report to ATC that manoeuvres are being executed as a result of a TCAS RA, controllers may be uncertain about an aircraft’s intentions and issue contradictory instructions, increasing the risk of collision.
Further, the operators’ TCAS RA phraseology differs from what is currently recommended by the International Civil Aviation Organization and Transport Canada. The phraseology currently in use by both operators calls for a TCAS event to be reported only as a TCAS-commanded climb or descent, and does not provide guidance on phraseology when following TCAS advice to maintain or adjust vertical speed.
If guidance provided to flight crews by operators includes phraseology that is not consistent with international best practices, ambiguous information regarding aircraft manoeuvring may be reported to ATC, increasing the risk of collision.
Given that the pilots did not report their responses to the TCAS RA as such, ATC personnel were unaware of the severity of the occurrence and did not contact the TSB immediately. As a result, the TSB did not have the data from the cockpit voice recorders quarantined in a timely manner, and the occurrence data was overwritten. If reporting of occurrences to the TSB is delayed, there is a risk that the cockpit voice data necessary to identify and communicate safety deficiencies will be unavailable.
Aircraft Registration Data
Aircraft registration data reproduced and distributed with the permission of the Government of Canada.
This article is published under license from Avherald.com. © of text by Avherald.com.
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