DH8D / DH8D, vicinity Sudbury ON Canada, 2016
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|On 14 October 2016, two Bombardier DHC8-400s received coordinated TCAS RAs as they came into opposite direction conflict near Sudbury, an uncontrolled airport, as one was descending inbound and emerging from an overcast layer and the other was level just below that layer after departing. Both aircraft crews ignored their RAs and their respective visual manoeuvring brought them to within 0.4nm at the same altitude. The Investigation noted that the conflict had occurred in Class ‘E’ airspace after the departing aircraft had cancelled IFR to avoid a departure delay attributable to the inbound IFR aircraft.|
|Actual or Potential
|Human Factors, Loss of Separation|
|Aircraft||BOMBARDIER Dash 8 Q400|
|Type of Flight||Public Transport (Passenger)|
|Origin||Greater Sudbury Airport|
|Intended Destination||Toronto/Lester B. Pearson International Airport|
|Take off Commenced||Yes|
|ICL / ENR|
|Aircraft||BOMBARDIER Dash 8 Q400|
|Type of Flight||Public Transport (Passenger)|
|Origin||Toronto/Billy Bishop Toronto City Airport|
|Intended Destination||Greater Sudbury Airport|
|Take off Commenced||Yes|
|ENR / APR|
|Location - Airport|
|Airport vicinity||Greater Sudbury Airport|
|Tag(s)||Aircraft-aircraft near miss,|
Event reporting non compliant,
Delayed Accident/Incident Reporting
|Tag(s)||ATC Unit Co-ordination,|
Procedural non compliance
|Tag(s)||TCAS RA Mis Flown,|
VFR Aircraft Involved
|Safety Net Mitigations|
|Malfunction of Relevant Safety Net||No|
|TCAS||Available but ineffective|
|Damage or injury||No|
|Causal Factor Group(s)|
Air Traffic Management
On 14 October 2016, a Bombardier DHC8-400 (C-GXJZ) being operated by Jazz Aviation on an Air Canada Express scheduled passenger flight from Sudbury to Toronto as JZA 604 and on an VFR clearance climbing out after takeoff from runway 22 and another Bombardier DHC8-400 (C-GKQA) being operated by Porter Airlines on a scheduled passenger flight from Toronto City to Sudbury as POE 533 and descending IFR but cleared for a visual approach to runway 04 received TCAS RAs in daylight due to their close proximity but still passed very close to each other to the southwest of the airport.
An Investigation was carried out by the Canadian Transportation Safety Board (TSB). FDR data was used to support the Investigation. Since ATC were unaware of the severity of the conflict, the TSB was not immediately informed of it and both CVRs were overwritten.
It was noted that the Jazz Aviation Captain had accumulated 21,000 hours total flying time and the First Officer, who was PF for the event sector, had accumulated 2,800 hours total flying time. Both pilots had 600 hours on type. Both the Captain and the First Officer of the Porter Airlines’ aircraft had accumulated 6,000 hours total flying time and the Captain, who was PF for the event sector, had 3,000 hours on type and the First Officer 1,200 hours on type. The ACC controller in position for the sector where the conflict occurred was found to have routinely handed over the position to another controller “just prior to” the occurrence of the conflict. Both controllers had significant experience as ATS personnel.
It was found that both aircraft had filed IFR flight plans and noted that Sudbury was an uncontrolled aerodrome with a Class ‘E’ CTZ with ATS provided by a ‘Flight Service Specialist’ (FSS). ATC to separate IFR traffic from other IFR traffic in the area was provided by the North Bay Sector of Toronto ACC. The controller there was using a radar display set to 250 nm so as to show the whole sector, which meant that 1cm of screen resolution represented approximately 5nm. In accordance with Unit Procedures, a single controller was responsible for this sector.
It was also established that runway 22 at Sudbury was the active runway with the ATIS broadcasting this information. The weather in the area was a slowly lowering overcast which the Sudbury METAR at the time of departure recorded as including good visibility below a cloud ceiling at 4500 feet agl. Observers stated that although there were no rain showers at Sudbury, such showers and/or virga were visible in the vicinity.
As the Jazz Aviation flight crew, in contact with the Sudbury FSS, taxied for runway 22, they were advised that there may be a delay in obtaining approval for an IFR departure because of inbound IFR traffic which intended to land on runway 04. Asked if they would accept a VFR departure from runway 22, they did so and the FSS requested and obtained approval for this from the North Bay controller, who asked the FSS to advise the crew that they could expect an IFR clearance when they were 20 nm south of Sudbury and that two inbound IFR aircraft, one of which was the Porter Airlines DHC8-400, were respectively 21 and 26 nm south of the airport at that time and both intending to land on runway 04. Based on previous experience of southbound VFR departures from Sudbury, the North Bay controller reported that they had “assumed that the departing aircraft would turn shortly after takeoff to clear the arrival path”.
Meanwhile, the North Bay controller had cleared the inbound Porter Airlines aircraft, still IMC, to descend to 5,000 feet QNH and route via the PEKVU waypoint located 10.1nm south west of Sudbury on the runway 04/22 extended centreline and on the RNAV approach to runway 04. The Porter Airlines crew, aware of the high overcast base, were expecting to conduct a visual approach once clear of cloud. They had called the Sudbury FSS and given an ETA of 1005.
At 0959:30, the Jazz DHC8-400 got airborne from runway 22 with the Porter Airlines aircraft “approximately” 17.3 nm south of the airport on track to PEKVU and passing 6700 feet QNH. A few seconds later, the Porter Airlines crew, still IMC, “requested further clearance from the North Bay controller” and were cleared for and accepted a visual approach to runway 04 and advised that the Jazz Aviation aircraft “was conducting a VFR departure from Runway 22 and would be instructed to turn to the west” and that the other IFR inbound was 10 nm south of the airport. The North Bay controller then called the Jazz Aviation aircraft and its crew advised that “they were levelling off at 4,000 feet QNH and were approximately 5 nm south of the airport”. The Jazz Aviation aircraft then turned left (east), 20° from the runway extended centreline without informing the controller - nor was this required since the aircraft had cancelled IFR in order to avoid a delayed departure. This turn was not seen on the radar display and the controller then informed the Jazz Aviation aircraft of the position or the Porter Airlines aircraft and they responded to the controller’s suggestion that they turn right (west) by stating that they would complete the turn shortly, but were delaying briefly due to some rain showers to the west.
About 10 seconds later, the Jazz Aviation aircraft, “which was approximately 6.1 nm south of the airport and in level flight at 4,000 feet, began a turn to the west”. The Porter Airlines aircraft was “approximately 12.6 nm south of the airport […] descending through 5,200 feet” and 20 seconds after this, the controller informed the Porter Airlines aircraft that the Jazz Aviation aircraft was now in their 1 o’clock relative position flying straight out from Runway 22 at 4,000 feet under VFR and turning to the west. After a further 30 seconds, the controller again informed the Porter Airlines aircraft that the opposing traffic was still in the same relative position 5 miles away opposite direction and at 4,000 feet. The Porter Airlines aircraft was at this time descending though 4,800 feet and the controller followed this call by “strongly suggesting” to the Jazz Aviation crew that they turn further to the west and that the opposite direction traffic was in their 12 o’clock relative position at 3 nm descending through 4,700 feet. They responded by beginning 23° bank turn to the right and informing the controller that they were turning west.
By this point, with the two aircraft closing at 330 knots and 2.7 nm apart, both aircraft received a TCAS TA and 10 seconds later, this was followed by a co-ordinated RA. These RAs were a corrective ‘CLIMB’ for the Jazz aircraft and a preventive ‘MAINTAIN VERTICAL SPEED, CROSSING, MAINTAIN’ for the Porter Airlines aircraft which was descending through 4,250 feet and still in cloud. The Porter Airlines crew reported that almost immediately they had emerged from the overcast and immediately seen the other aircraft. However, instead of maintaining the 1,900 fpm rate of descent they had when the RA occurred, once visual, they briefly reduced it to 700 fpm which as they passed 4,150 feet, received a further RA this time to ‘INCREASE DESCENT’ which they did whilst also initiating a 40° banked turn to the right.
Meanwhile, the Jazz Aviation aircraft had not commenced a climb. Although the First Officer had disconnected the AP in order to do so, the Captain, having visually acquired the other aircraft on the left, had taken control and reported having “decided against climbing due to the overcast cloud layer above” believing that with the other aircraft in sight, a turn to the right away from it “would be an appropriate evasive manoeuvre”. The Captain then manoeuvred the aircraft further to the right and increased the bank angle to 40° whilst also briefly descending at 1,000 fpm from 4,000 feet to 3,880 feet before returning to 4,000 feet.
The combined consequence of these responses was that the two aircraft were now 1.1 nm horizontally and 178 feet vertically apart and still closing at over 300 knots. The Porter Airlines crew reported to the controller that they were “turning” and, three seconds later, the Jazz Aviation crew reported that they were “climbing”. Neither of these calls included mention of any TCAS RA. A few seconds after these transmissions when about 9.5 nm southwest of Sudbury Airport, the two aircraft reached their minimum separation, 0.4 nm horizontally when both at the same altitude - approximately 4,000 feet.
Five seconds later, the Jazz crew reported that they were “clear of the conflict” and in acknowledging this, the controller instructed them to maintain flight under VFR and then instructed the Porter Airlines aircraft to “continue with the visual approach to runway 04” and contact Sudbury. The Jazz Aviation aircraft was subsequently provided with its en route IFR clearance to destination.
Observations on the context of the conflict
- Although the inter-unit arrangement between the Toronto ACC and the Sudbury FSS included the requirement that the ACC shall, “during VMC, confirm the runway in use with the FSS prior to clearing an aircraft for an approach to a specific runway”, there had been no communication about which runway was active prior to the issue of a clearance to the PEKVU initial approach waypoint for runway 04.
- The handover of position at the North Bay ACC sector did not identify the active runway at Sudbury, although the inbound aircraft’s clearance to PEKVY for a 04 approach was briefed.
- In respect of the ACC re-clearance for the inbound aircraft to make a visual approach, it was found that the controller had not followed MATS guidelines specifying that in “single-approaching-aircraft situations, the pilot [must report] sighting the airport” before a controller can authorise it to make a visual approach.
- The Porter Airlines crew accepted the visual approach authorisation given even though they were still in cloud - and would remain so until just before the near miss.
- The aircraft type involved allows the TCAS traffic display to be continuously displayed on the MFD - ‘continuous mode’ - or to only show TA and RA indications - ‘automatic mode’. When the transponder is initially selected on prior to departure, the TCAS display defaults to the automatic mode and to change to continuous mode, the TCAS must be pressed and the range selected to 40 nm or less on the EFIS control Panel. Porter Airlines’ Standard Operating Procedures (SOPs) required that the TCAS traffic display should be on screen continuously and set to a range of 40 nm or less in the cruise and their crews were “trained to keep the range at 40 nm or less during an approach in order to have a complete picture of the approach display and traffic information”. Both Porter Airlines’ pilots had their respective TCAS settings configured to a continuous TCAS traffic display. There were no Jazz Aviation SOPs requiring full time use of the continuous mode and this matter was left to crew discretion. When the Jazz Aviation aircraft departed Sudbury, the Captain’s panel remained in the default automatic mode and the First Officer’s panel was set to continuous mode. The First Officer’s panel was subsequently switched to automatic mode at around 2200 feet QNH and then back to continuous mode 50 seconds prior to the RA.
- In respect of following a TCAS RA, Porter Airlines’ SOPs state that compliance with a TCAS RA is mandatory and note that “it is possible to confuse other traffic in close proximity with an unseen aircraft which is the real threat”. They call for the PF to “disconnect the autopilot and initiate a climb or descent as required to follow the TCAS avoidance manoeuvre”. Whilst Jazz Aviation SOPs also specified that compliance with a TCAS RA was mandatory, they “allow for some discretion if the Captain is of the opinion that to do this would compromise the safe operation of the flight or unless the flight crew has more accurate information (e.g. confirmed visual contact) about the intruder causing the RA”. Various cautions accompanied this discretion including that “it may be difficult to judge the vertical and/or horizontal displacement of (a conflicting aircraft) […] especially when at cruise altitude or when the horizon is obscured or distorted by cloud layers” as in the investigated case.
- Notwithstanding the fact that neither aircraft reported their RAs on the air traffic frequency being worked, the SOPs of both the operators involved were found to require not only that the PM make such a report but also to stipulate the use of phraseology that differed from that currently recommended by Transport Canada and the ICAO in that it required the direction of a (corrective) vertical deviation during an RA to be given.
The formally-stated Findings as to Causes and Contributing Factors were as follows:
- 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 whereby 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 flight 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 flight POE 533 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 two aircraft.
- The Porter Airlines 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 two aircraft.
Three formally-stated Findings as to Risk were as follows:
- 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 Final Report of the Investigation was authorised for release on 17 January 2018 and it was officially released on 23 January 2018. The Investigation was not made aware of any Safety Action taken following this event and no Safety Recommendations were made.