Land And Hold Short Operations in Melbourne under review or how media blow an occurrence completely out of proportion

Last Update: August 6, 2018 / 13:58:11 GMT/Zulu time

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Australian Media at the current are breaking headlines of a "Near Miss" at Melbourne Airport after a passenger video surfaced showing an occurrence, investigated by the Australian TSB, in which two aircraft were on simultaneous approaches to runway 27 and to crossing runway 34 (with the instruction to land on runway 34 and hold short of runway 27) and a third was departing Melbourne on Jul 5th 2015. The ATSB, in their factual report, reported however: "There was no loss of separation between any of the aircraft."

The ATSB reported however, that as the result of the simultaneous go arounds on both runways 34 and 27 the LAHSO (Land And Hold Short Operations) operation at Melbourne has been suspended pending a review.

The Aviation Herald was aware of this factual report since its release on December 8th 2015, and although interesting with the respect to the review of the "LAHSO", land and hold short operations, procedure found the report was outside the scope of the coverage.

The ATSB wrote in their factual report that a Boeing 777-300 registration A6-EBU was departing Melbourne from runway 34, a Boeing 737-800 registration VH-VYE was on a right downwind for a visual approach (with about 5.5nm to touchdown remaining) to runway 34 cleared to land with the instruction to hold short of runway 27 and another Boeing 737-800 registration VH-VXS was on an instrument approach to runway 27 about 7nm before touchdown.

A trainee controller (ADC trainee), supervised by fully licensed on the job training instructor (OJTI), was on duty on Melbourne's tower at the time, a coordinator holding operational command authority was supervising activities at Melbourne tower.

The ATSB described the actual occurrence:

At 1808, the flight crew of the 777 reported ready for departure off R34. The departure from this runway, rather than from the designated departure runway for LAHSO, was an operational requirement due to the aircraft’s weight and the resulting increased length of runway needed for take-off. At that time, VXS was on about a 7 NM (13 km) final for R27 and VYE was on a right base for R34, with about 5.5 NM (10 km) to run.

After confirming that the 777 flight crew was ready for an immediate departure, and discussing the situation with the OJTI, the ADC trainee instructed the 777 flight crew to line up on R34.

At 1809, the ADC trainee issued the 777 flight crew with a clearance for an immediate take-off. At that time, VXS was on about a 4 NM (7.4 km) final for R27 and VYE was turning right base and about 3.5 track miles[3] (6.5 km) from the threshold of R34.

As the flight crew of the 777 commenced the take-off roll, the Coordinator voiced concern to the ADC trainee and OJTI that the traffic scenario involving the three aircraft was not going to work.

At 1810, after instructing VXS’s flight crew to reduce to minimum speed, the ADC trainee advised them that, in the event of a missed approach, there was traffic departing and landing on the crossing runway and they should climb to 4,000 ft ‘expeditiously’. The trainee’s intent was to pre-warn the flight crew of the need to expedite their climb in the event of a missed approach. However, VXS’s flight crew interpreted the transmission as a requirement for an immediate missed approach and expedited their climb to 4,000 ft.

After observing VXS commencing a missed approach from R27, and with the 777 still on the take-off roll on R34, the Coordinator directed the ADC trainee to send VYE around. The ADC trainee issued the instruction to VYE’s flight crew and they commenced a go-around.

The Coordinator reported that their instruction to the ADC trainee was given under a duty of care to prevent a potential safety occurrence and not as part of their OCA role. However, the ADC trainee and OJTI reported that they considered the required runway separation between the departing 777 and VYE would have been achieved had VYE continued the approach.

The ADC trainee identified that VYE, in the go-around manoeuvre, could encounter wake turbulence from the departing 777. The trainee and OJTI discussed the situation and determined that instructing VYE to turn right would keep the aircraft out of the 777’s wake turbulence envelope. The ADC trainee instructed VYE’s flight crew to turn right and ‘track’ 360°.

The ADC trainee’s intention was to issue a heading instruction but they used phraseology consistent with a procedural tracking requirement. VYE’s flight crew read back ‘heading 360°’, which was 14° right of R34’s magnetic heading of 346°.

The minimum vector altitude,[4] which has application in instrument meteorological conditions[5] or at night, in that area was 2,000 ft. At the time the ADC trainee issued the instruction to VYE, the aircraft’s altitude was about 1,400 ft and climbing. At about 1811, when VYE crossed the intersection of R34 and R27, the aircraft was in the right turn and above 2,000 ft.

VXS and VYE subsequently landed at Melbourne and the 777 continued to Singapore.

On Aug 6th 2018 the ATSB released their final report concluding the probable causes of the incident were:

- The decision to clear the flight crew of A6-EBU for an immediate take-off, combined with the aircraft’s slower than anticipated rate of movement, resulted in it coming into proximity with VH-VXS and VH-VYE.

- The proximity between A6-EBU, VH-VXS and VH-VYE resulted in the flight crew of VH-VXS on final for runway 27 electing to go around and the flight crew of VH-VYE on final for runway 34 being instructed to go around on the direction of the Melbourne Coordinator.

- Although initiated due to a safety concern, the decision by the Melbourne Coordinator to instruct the crew of VH-VYE to go around resulted in an airborne loss of separation compared to a potential loss of separation on the ground.

- The simultaneous go-arounds conducted by VH-VYE and VH-VXS, sequenced to land on intersecting runways under land and hold short operations at Melbourne Airport, resulted in the controller issuing a radar vector to the flight crew of VH-VYE while the aircraft was below minimum vector altitude to assure surveillance and wake turbulence separation.

- The radar vector issued at night to the flight crew of VH-VYE when no other options were available, though intended to ensure wake turbulence and surveillance separation behind A6-EBU and separation assurance with VH-VXS, did not assure terrain and obstacle clearance.

- The hazard associated with the inability to separate aircraft that are below the appropriate lowest safe altitude at night was identified but not adequately mitigated. This resulted in a situation where, in the event of a simultaneous go-around at night during land and hold short operations at Melbourne Airport, there was no safe option available for air traffic controllers to establish a separation standard when aircraft were below minimum vector altitude. [Safety issue]

Other factors that increased risk

- The lack of night-time compromised separation training scenarios for the Melbourne Air Traffic Control Tower controllers increased the risk of the controllers responding inappropriately when aircraft were in proximity at night.

- The automated sequencing system used by Airservices Australia at Melbourne Airport (MAESTRO) did not ensure that two aircraft would not arrive at the intersection of the runways at the same time during land and hold short operations, increasing the risk of unsafe proximity at the intersection.

The ATSB reported, other than in their initial factual report, that the separation between the two 737s reduced to 900 feet vertically and 0.9nm horizontally stating: "Airservices Australia (Airservices) surveillance data showed that separation between the two B737s reduced to about 0.9 NM (2 km) and 900 ft as VXS crossed runway 34 in front of VYE, climbing in the missed approach on runway 27. At that time, VYE was also climbing, conducting a go-around from runway 34. The tower controller was responsible for maintaining a separation standard and the only available standard was visual.15 However, due to the limitations of human vision at night16 and the disposition and trajectory of traffic at the time, visual separation could not be assured."

The ATSB analysed:

On the night of this occurrence, in the gap between arrivals sequenced to runway 34, one off-mode departure had already used runway 34 prior to the B777 being lined up. Though the flight crew of the B777 had received the current Automatic Terminal Information Service22 stating that LAHSO were in use, being an international operator, the flight crew may not have been aware that both runways at Melbourne Airport were being used for simultaneous arrivals and they were not told about the B737s on final for both runways.

In a statement, the captain of the aircraft on final for runway 27, VH-VXS (VXS), reported he had heard the instruction to the B777 for an immediate departure. After observing the preceding aircraft depart from runway 34, he believed that his aircraft would be in close proximity to the B777 when they landed, so he had asked the first officer to prepare for a missed approach. Shortly after, and having determined that there was insufficient spacing with the B777, the captain instructed the first officer to initiate a missed approach as the B737 was approaching 500 ft above ground level.

The coordinator became concerned about the sequence when he realised that the flight crew of the B777 had not been advised of the B737 (VXS) going around from final runway 27. Due to the limitations of human vision at night, judgement of distance is extremely difficult, and the coordinator was concerned that the B777 flight crew may have elected to initiate a rejected takeoff if they perceived the B737 as a possible threat. If the B777 had rejected the take-off and remained on the runway, there may have been insufficient runway behind that aircraft for the landing roll of the B737 on final for runway 34, VH-VYE (VYE). Additionally, the coordinator was concerned that there was a high probability that the runway separation standard would not beachieved between the B777 and VYE.

The coordinator communicated his concerns to the trainee tower controller and the tower OJTI. On receiving what he deemed an unsatisfactory response, and believing the situation to be safety- and time-critical, the coordinator instructed the trainee tower controller to send VYE around. The trainee tower controller and the tower OJTI later reported that, as the B777 commenced the take-off roll, they also had concerns about the sequence and the potential for a loss of separation between the two aircraft using runway 34. However, immediately prior to that they both thought that the sequence, while ‘tight’, would work. In that context, if separation relies on an expected rate of aircraft ground movement that may not occur, it is prudent to have an alternative plan. This is more important if the involved aircraft is large and/or operated by international flight crew who may be less familiar with the airport. However, on this occasion the actions of the B777 flight crew were appropriate.

Given the specific LAHSO phraseology required to be used by the Tower controller, and the necessity for a read back by the flight crew of VYE of the restriction to hold short, there may have been insufficient time available for the trainee tower controller to clear both arriving aircraft to land.

The trainee tower controller, on her first exposure to LAHSO, had about 29 seconds to:

- issue a landing clearance to the flight crew of VYE, including the restriction to hold short of runway 27
- receive a correct read back of the restriction from the flight crew
- issue a landing clearance to the flight crew of VXS, including advice that VYE was landing on runway 34 but would hold short of runway 27.

Had the line-up and take-off clearance for the B777 been delayed, the two B737s would have landed under LAHSO and the B777 could have then departed without any time pressure. Alternatively, the provision of traffic information on the two B737s to the flight crew of the B777 would have made them aware of the traffic situation and provided the option of expediting their departure or remaining clear of the runway.

With respect to the unsafe proximity of aircraft the ATSB analysed:

Two aircraft arriving simultaneously for different runways during LAHSO are separated by the requirement that one aircraft lands and stops prior to the intersection of the runways. When one or both aircraft however, conduct a missed approach, another separation standard is required. The only available standard was visual. As both aircraft were tracking towards the runway intersection, the controller could not be assured that visual separation would be maintained as the judgement of distance at night is limited by the physiology of the human eye.

Airservices surveillance data showed that separation between the two B737s reduced to about 0.9 NM (2 km) and 900 ft as VXS crossed runway 34 in front of VYE, as VXS climbed in the missed approach on runway 27. At that time, VYE was also climbing, conducting a go-around from runway 34. The tower controller was responsible for maintaining visual separation; however, due to the limitations of its application at night, a surveillance (radar) separation standard of 3 NM (6 km) or 1,000 ft was arguably more appropriate.

As a clearance to land is also a clearance to conduct a missed approach, controllers should have a plan for such an eventuality and act on that plan in a timely manner.

The action of the coordinator in instructing the trainer tower controller to send VYE around changed what was a potential loss of runway separation into a loss of separation between airborne aircraft.

With respect to radar vectors issued below minimum radar vectoring altitude the ATSB analysed:

Though VYE, while going around on runway 34, did not fly through the flight path of the B777 as it executed the go-around, it was 1.5 NM (3 km) behind the B777 instead of the required wake turbulence standard of 5 NM (9 km). The radar vector and caution were issued by the trainee tower controller to expedite the re-establishment of a standard. Additionally, the radar vector increased the divergence between the flight paths of the two B737s when VXS was 0.9 NM (2 km) ahead of VYE and 900 ft above, passing from the right to left.

When an aircraft is vectored by a controller, the responsibility for navigation and terrain clearance is transferred from the flight crew to the controller. A MVA is calculated to ensure terrain clearance at the stated minimum levels and vectoring below the MVA would only be conducted in an emergency situation. At the time of the occurrence, the coordinator believed that the situation was both time- and safety-critical, and he deemed that issuing a radar vector below MVA was the only course of action available, and that action had earlier been sanctioned by his manager. As such, he told the trainee controller to issue the radar vector to the flight crew of VYE.

With respect to hazard analysis and mitigation the ATSB anlysed:

Though Airservices was aware of the hazard from at least October 2011, as noted by CASA, in early 2013 the only controls put in place or proposed were preventative in nature i.e. designed to reduce the risk of an aircraft conducting a missed approach at night during LAHSO at Melbourne Airport. Not until 2016 did Airservices put in place a recovery control25 – a surveyed area where aircraft could be radar vectored when below MVA at night. Had Airservices pursued a recovery control after the 2011 occurrence, the radar vector issued by the trainee tower controller would have been in accordance with documented procedure and training, and would not have resulted in a breakdown of separation with terrain.
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This article is published under license from Avherald.com. © of text by Avherald.com.
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