ANSP info/procedural error

After landing on runway 27 the crew of VH-TAD commenced taxiing the aircraft along taxiway echo, back to the terminal. It was necessary to obtain a clearance to cross runway 34 on the way in.

In the control tower the aerodrome controller issued a clearance to another aircraft to take off on runway 34. He also gave approval to the surface movement controller to allow VH-TAD to cross runway 34 behind the aircraft taking off.

The surface movement controller then issued a clearance for VH-TAD to cross runway 34. In doing this he omitted to say to cross behind the departing aircraft. The crew of VH-TAD saw the other aircraft taking off on runway 34 and held VH-TAD short of runway 34 until the other aircraft had passed.

Significant Factor

The following factor was considered relevant to the development of the accident:

1. The surface movement controller incorrectly issued a clearance for VH-TAD to cross runway 34, in lieu of saying to cross behind the aircraft taking off on runway 34.

The initial clearance passed to the crew of VH-TJB was for cruise at FL 350. Sector 3E contacted Launceston Tower with an amendment for the aircraft to cruise at FL 330. After departure the crew reported on climb to FL 350.

The error happened because the Launceston Aerodrome Controller became pre-occupied with another task and omitted to pass the amended level details onto the crew. The situation was recognised and resolved before the aircraft reached FL 330.

The pilot of the first aircraft in the sequence, from Australian Airlines, requested direct track from over Devonport to Hobart on the 320 radial. On co-ord with Hobart Air Traffic Control approval given for this and a second aircraft, this one from Ansett Airlines, to also track direct. The Sector 3 controller passed the clearance to the first aircraft but forgot to pass it to the second one. The second aircraft arrived in the Hobart area on the 301 radial, which was the original planned route, instead of the 320 radial as expected. No loss of separation occurred.

VH-FCE departed Coffs Harbour for Williamtown at 1237 ESuT and was maintaining 10,000 ft with an estimate for Taree of 1307.

VH-TQQ departed Sydney for Port Macquarie at 1231 and passed over Williamtown at 1252 while cruising at FL170 with estimates for Taree of 1307 and Port Macquarie 1314. Air traffic control (ATC) cleared VH-TQQ to leave the control area on descent and at 1305 VH-TQQ reported leaving FL170 and was instructed to contact Sydney on the area frequency.

At 1306 VH-TQQ made an all stations call on area frequency and reported having left FL170 on descent to Port Macquarie. The flight service officer (FSO) notified VH-TQQ of the Area QNH and advised that there was no IFR traffic. At 1308 the FSO advised VH-TQQ that there was traffic at 10,000 ft and the crew replied they had just sighted VH-FCE while passing through that aircraft's level.

During the subsequent investigation, the crew of VH-TQQ stated that they were descending at 1700 ft/min and were approximately 1 NM east of track. While conducting a normal lookout scan, they sighted VH-FCE approximately 1 to 2 NM to their left and an estimated 2,000 ft to 3,000 ft below.  As they could maintain visual contact, they decided that no evasive action was needed. The captain stated that had he received traffic information on VH-FCE he would have levelled off above 10,000 ft until positive passing had been established.

The crew of VH-FCE stated that they were on track and over Taree when they sighted VH-TQQ descending from approximately 1,000 ft above and 2 NM left of their aircraft. They confirmed that they heard VH-TQQ make the area transmission and were looking out for the aircraft but decided it was not necessary to respond to this transmission. They also decided that as they could see the aircraft no evasive action was necessary.

The FSO's evaluation of the situation was influenced by the phraseology used by the Sector 2 controller who indicated to the FSO that VH-TQQ would call requesting traffic information on area frequency at top of descent. The FSO had sufficient information on hand to alert both aircraft. However, when VH-TQQ called at 1306 she calculated that the time of passing would occur at 1307 and that in this time period VH-TQQ would not have descended 7,000 ft. Based on this assessment the FSO chose not to pass traffic information to the two aircraft.

CONCLUSION

Significant Factors

The following factors were considered relevant to the development of the incident.

1. The FSO incorrectly assessed a traffic conflict situation and did not pass traffic information to the crews of VH-TQQ and VH-FCE.
2. The co-ordination procedures used between ATC and FS contributed to the FSO's incorrect assessment.
3. The crew of VH-FCE had prior knowledge of the presence of VH-TQQ but decided not to respond toVH-TQQ's descent call.

SAFETY ACTION

As a result of the Bureau's investigation the Civil Aviation Authority, inter alia, reviewed the phraseologies used between Air Traffic Control and Flight Service in relation to aircraft proceeding into or out of controlled airspace.

VH-TQR [DHC8] was maintaining Flight Level [FL] 200 on the CRAVEN - Port Macquarie track on a flight from Sydney to Port Macquarie. A clearance was obtained by Sydney Sector 2 from Williamtown Air Traffic Control [ATC] for VH-TQR to transit Restricted Area R594A at and on descent from FL200. The aircraft was authorised to leave control area on descent.

RAAF Air Defence personnel were controlling MAPLE 32 [FA 18] and were instructed by Williamtown ATC to ensure that the aircraft would remain east of the CRAVEN - Port Macquarie track. During vectoring procedures, the Air Defence Controller allowed MAPLE 32 to cross this track and come into conflict with VH-TQR. The Senior Controller observed this situation and initiated appropriate co-ordination to rectify the confliction.

There was approximately two minutes delay before the exact information reached the Air Defence Controller responsible for MAPLE 32 and by the time separation was guaranteed, the aircraft had passed the point of nearest contact.

On observing the potential conflict, Sydney Sector 2 instructed VH-TQR to maintain FL190 in an attempt to provide separation. The controller had observed the altitude read out of MAPLE 32 to be FL186 and knew that VH-TQR had left FL200 on descent. VH-TQR reached FL187 prior to maintaining FL190.

The aircraft came within 6.3nm and 100ft of each other. As the radar separation standard is 5nm, no breakdown in separation occurred.

Significant Factors

1. The Air Defence Controller did not comply with the Air Traffic Control instruction received.

2. The time taken for the Senior Controller to co-ordinate with the Air Defence Controller placed the separation standard in jeopardy.

FACTUAL INFORMATION

A Shorts SH36 aircraft had departed Williamtown on a flight to Brisbane. The crew were maintaining the aircraft at 9,000 ft outside controlled airspace and were in contact with Flight Service Area 5 (FIS 5).

A Dash 8 aircraft had departed Sydney on a flight to Taree. The crew were maintaining the aircraft at flight level (FL) 150 and were under the control of Brisbane Sector 15C.

The sector controller coordinated the overhead Williamtown position of the Dash 8 with FIS 5. This coordination included an estimate for Taree and advice that the crew would contact FIS 5 at "top of descent".

The flight service officer correctly calculated that the two aircraft would be in conflict and passed traffic information on the Dash 8 to the crew of the SH36. Although aware of a requirement to back coordinate with sector control when an aircraft leaving controlled airspace on descent required traffic information, the officer elected not to pass the information to the sector controller. She had calculated that there would be at least 3 minutes between the top of descent of the Dash 8 and the aircraft coming into conflict and therefore sufficient time for her to pass the traffic information to the crew.

The crew of the Dash 8 were cleared to leave controlled airspace on descent to Taree and were instructed to contact FIS 5 by sector control, immediately after they reported leaving FL150. They attempted to do this but were delayed by other airspace users transmitting on that frequency. They finally made their broadcast while passing 13,000 ft and at a rate of descent of 1,800 ft/min. The base of controlled airspace in the Taree area was 12,500 ft. The Aeronautical Information Publication required a crew to make their first broadcast on the flight information service frequency prior to leaving controlled airspace.

The flight service officer acknowledged the transmission from the crew of the Dash 8 and passed the traffic information on the SH36 and two other aircraft. By the time the crew had analysed this information and assessed that the SH36 was in direct conflict, their aircraft was passing between 11,000 ft and 10,500 ft. The pilot in command immediately amended the altitude selection to 10,000 ft and the automatic pilot commenced the level-off manoeuvre at 10,400 ft. The aircraft levelled off at 10,000 ft and the crew saw the SH36 in their 12-o'clock position. Both crews had been using Global Positioning System navigational equipment and were accurately "on track".

The two crews then established communication and mutual sighting. There was no breakdown of separation, and the crews completed a safe sighting and passing manoeuvre.

ANALYSIS

Analysis of the respective flight paths indicated that the aircraft avoided a direct conflict by approximately 30 seconds. Both crews agreed that their respective aircraft were on-track and the position of the SH36 was such that the closing speed and descent profile of the Dash 8 could have resulted in a mid-air collision had the rate of descent not been arrested.

The level-off of the Dash 8 was implemented as soon as the crew had analysed the position of the SH36 and before they achieved visual contact. Had they been delayed further in their attempts to contact FIS 5, the separation would have been significantly reduced.

The flight service officer had received the correct coordination from the sector controller and made a correct assessment of the conflict. However, her decision not to bother air traffic control with the need to pass traffic information was predicated on an assumption that the crew of the Dash 8 would call her at top of descent. If such a call was made, it would have given her more than 3 minutes to carry out the broadcast and this would probably have been sufficient for the task. However, such a timely call could not be guaranteed and on this occasion did not happen. The resultant delay reduced the time available for the crew to make an informed judgement about the traffic.

The phrase "top of descent" was used by the controller to indicate a transfer of the aircraft to FIS 5 as soon as practicable after the crew reported leaving their cruising level. The regulations allowed the crew to report vacating a level up to 1 minute after the event. A further delay in making the broadcast then occurred due to other airspace users making authorised transmissions. This delay could not be accurately estimated and was always going to be of unknown duration.

The flight service officer considered that the phrase "top of descent" meant exactly that and made an assessment based on this belief.

SIGNIFICANT FACTORS

1. The flight service officer elected not to coordinate the traffic information on the SH36 to the crew of the Dash 8 with Sector Control.

2. The flight service officer expected the crew of the Dash 8 to contact her at "top of descent".

3. The crew of the Dash 8 were delayed in making the initial broadcast on FIS5 due to frequency congestion.

SAFETY ACTION

Airservices Australia Northern District Office issued a local instruction (NDO 97/191) on 29 August 1997 which specified improved procedures for the transfer of communications to flight information service frequencies when an aircraft is on descent from controlled airspace.

As a result of this and other occurrences, the Bureau of Air Safety Investigation is developing recommendations relating to the provision of timely traffic information by air traffic services and for flight crews to develop separation assurance techniques.

Any recommendations arising will be published in the Bureau's Quarterly Safety Deficiency report.

FACTUAL INFORMATION

A Boeing 767 (B767) aircraft departed Perth for Melbourne on climb to the flight planned level of flight level (FL) 370. The aircraft was being controlled by Melbourne Sector 1. This position was a procedural control position which used flight progress strips (FPSs) to manage aircraft separation. A number of FPSs were required for each aircraft under control. The FPSs designated the planned route of an aircraft.

After reporting at RERON, a position southeast of Perth, the crew requested a change of level to FL330. The change of level was approved by the Sector 1 controller. The controller annotated the new level of FL330 on the B767's FPSs.

While the Sector 1 controller was receiving coordination on three other aircraft from Perth Flight Service the crew of the B767 requested a change of level to FL350. The Sector 1 controller approved the change of level and then completed the coordination. The controller did not annotate the B767's RUFLE position FPS, the last FPS for the aircraft, with the amended level. This FPS indicated that the B767 was to operate at FL330.

The Sector 1 controller transferred the B767 to Perth Flight Service (FS) to maintain communications via High Frequency (HF) radio. The FS operator passed the B767's RIDLE position to the Sector 1 controller after the crew reported at that position. The aircraft's level of FL350 was reported to, and correctly read back by the Sector 1 controller.

The Sector 1 controller was then relieved at the position by another controller. The two controllers conducted a handover/takeover of the position. The relieved controller could not remember conducting a final check of the FPSs, as was his normal practice, before leaving the position.

The crew of the B767 reported to the new Sector 1 controller that the aircraft was now back on Very High Frequency (VHF) radio and was at position ROMPA at FL350 at 54 (time 1754 UTC). The Sector 1 controller coordinated the position report to Adelaide Sector 4 but read the level of FL330 from the RUFLE FPS. The Adelaide Sector 4 controller read back and annotated the B767 FPS with FL330. During this coordination sequence the Sector 1 controller was interrupted by a transmission from another aircraft.

The crew of the B767 subsequently transferred to Adelaide Sector 4 and reported at RUFLE at FL350. There was no breakdown of separation.

Sector 1 was combined with Sector 5. Traffic was light and less than normally experienced at the position for the time of day. The first controller had worked until 1300 ESuT that morning and then returned for the evening "Doggo" shift at 2300. He had two hours sleep in the afternoon and felt rested. He operated the position from approximately 0300 to 0445.

ANALYSIS

There were two opportunities to correct the error after the relieving controller assumed responsibility for the position. The first being when that controller started operating at the position and the second when the crew of the B767 reported at ROMPA at FL350. However, the incorrect annotation on the RUFLE FPS was not detected.

The reason for these errors not being detected or why the first controller did not annotate the RUFLE FPS could not be ascertained. It was probable that the physiological effects due to the early time of day and the low level of activity combined to reduce the controllers' vigilance and/or use of standard practices.

SIGNIFICANT FACTORS

1. The Sector 1 controller did not annotate all the B767 FPSs with the approved level of FL350.

2. The relieving controller did not detect the error in the RUFLE FPS during or after the handover/takeover.

FACTUAL INFORMATION

An instrument flight rules (IFR) Piper Chieftain (PA-31-350) departed Wynyard for Moorabbin on climb to 8,000 ft. Five minutes later an IFR Beechcraft Baron (D55) departed Smithton for Bankstown, tracking via East Sale, on climb to 9,000 ft. The intended tracks of the aircraft crossed at a position approximately 50 NM north of Wynyard. The PA-31-350 was operating a regular transport flight while the D55 was on a charter flight. The visibility was in excess of 20 km and there was no cloud below 10,000 ft.

Both aircraft were operating in uncontrolled, class G, airspace. The crews of IFR aircraft operating in class G airspace are required to be provided with information on other IFR traffic by the responsible air traffic services (ATS) operator. The area in which the flights were operating was the responsibility of the Melbourne Sector 3 Low controller.

The Sector 3 Low controller had been rated in the position for approximately five months. Traffic levels were high and there was a considerable number of radio transmissions that required her attention. The controller advised traffic information, with the exception of the PA-31-350, to the pilot in command (PIC) of the D55 when that aircraft was taxiing at Smithton. She had previously advised traffic information on four other IFR aircraft to the PIC of the PA-31-350. Flight details of all aircraft were available to the controller on flight progress strips.

The controller endeavoured to plot the tracks of the two aircraft on a chart to assess whether they would conflict. However, she was distracted by radio transmissions and by the need to conduct co-ordination with other ATS positions and was unable to complete the plot.

There was provision for a planner controller, adjacent to the Sector 3 Low controller's position, but it was not occupied. The normal practice was to staff the Sector 3 Low position with a single operator. The team leader was available to assist the controller, but the controller was satisfied with the situation and did not think assistance was required.

The PIC of the PA-31-350 had maintained his aircraft at 5,000 ft to avoid two other aircraft inbound to Wynyard on the route. As he recommenced climb to his planned level of 8,000 ft he sighted an aircraft to his left. This aircraft appeared to be on climb and was at a distance of approximately 2 NM. The PIC of the PA-31-350 was aware that the converging aircraft was the D55, as he had previously heard the PIC of that aircraft arranging separation with the crews of other aircraft. The PIC of the PA-31-350 established communications with the PIC of the D55 who advised that he had the PA-31-350 in sight and would restrict his climb to pass below that aircraft. The two aircraft passed with approximately 300 ft vertical separation.

ANALYSIS

The controller was not sure whether the tracks and levels of the two aircraft would cause them to conflict and had endeavoured to plot the tracks to clarify the situation. A more experienced controller, faced with the same concern in a high workload period, may have passed traffic information to the two crews in lieu of increasing the complexity of the task by plotting the tracks. This action would have required little effort in comparison to drawing and assessing a plot of the intended tracks. In addition, the immediate provision of traffic information would have been more expeditious and would have ensured that the pilots received the information in sufficient time to co-ordinate their mutual separation.

The operation of the position by a single controller was adequate for the majority of traffic situations. However, the supervisor should have recognised the increasing complexity of the situation and offered the inexperienced controller some assistance during the high workload period when she was probably becoming task saturated. The limited experience level of the controller probably prevented her from recognising her own level of task saturation.

The situational awareness and visual scan of the pilot in command of the PA-31-350 assisted him in sighting and co-ordinating separation with the other aircraft.

SIGNIFICANT FACTORS

1. The Sector 3 Low controller's limited level of experience.

2. The complexity of the traffic situation due to the high number of radio transmissions.

3. Inadequate monitoring of the controller's workload by the supervisor.

FACTUAL INFORMATION

The crew of a B737, en route from Perth to Melbourne, requested an arrival on runway 34 after receiving the automatic terminal information service (ATIS) information 'W', which indicated that runway 27 was available for arrivals and runway 34 was available for departures. During the period between the crew receiving the ATIS and requesting runway 34, the aerodrome information changed. The latest ATIS information 'V', which the crew copied, indicated that Melbourne aerodrome was operating on runway 27 for departures and runway 16 for arrivals. The crew was advised that runway 34 was not available, due to the operations on runway 16, and was assigned a standard arrival route (STAR) clearance and runway 16. The crew did not hear the assigned runway because of radio interference and requested confirmation from the sector controller that the runway was 27. The sector controller replied that runway 27 was the assigned runway. The sector controller annotated runway 27 on the flight progress strip for the aircraft. The crews of subsequent aircraft were assigned runway 16 by the sector controller.

The crew of the B737 had not advised the sector controller of the code and receipt of the ATIS, nor had the controller verified that the crew had received the latest ATIS.

When the non-duty runway was assigned, the controller was required to annotate the "ops data" line of the aircraft's label on the radar display with the assigned runway. The "ops data" line for the B737 was not annotated with runway 27. Once the runway and the arrival clearance had been issued by the sector controller, there were no further checks to confirm the aircraft's arrival clearance or assigned runway.

The crew had previously requested track shortening and thought that the sector controller was actioning this request by assigning a runway which required fewer track miles to run to a landing. The crew transferred to approach control and continued to track in accordance with the cleared route. Overhead Essendon aerodrome, the crew continued to track eastwards for a left base to runway 27. The approach controller was expecting the B737 to turn left, to the north, for a left base to runway 16. The approach controller cancelled the standard arrival route and radar vectored the B737 for runway 16. As the B737 approached the centreline of runway 27, the crew requested from the controller the runway to which the aircraft was being radar vectored. The approach controller advised them that the vectors were for runway 16. The aircraft landed on runway 16. There was no breakdown of separation.

ANALYSIS

Initially, the sector controller issued the correct STAR and runway to the crew of the B737. However, when the crew queried the assigned runway, the controller replied with the incorrect runway and then annotated the flight progress strip with the wrongly assigned runway. The reason for the controller assigning the incorrect runway and not amending the "ops data" line of the label could not be determined.

The crew of the B737 did receive the latest ATIS but believed that the sector controller was providing them with their previously requested track shortening by assigning them runway 27. Consequently, they did not query the runway assignment with the Approach controller.

SIGNIFICANT FACTORS

1. The controller did not confirm that the crew of the B737 had received the latest ATIS.

2. The sector controller did not confirm the arrival runway, as indicated in the latest ATIS, when queried by the crew.

3. The sector controller did not amend the "ops data" line of the B737's label on the radar display with the assignment of the non-duty runway.

1. Reversal of the flight levels of the two eastbound aircraft.  That is, giving the actual flight level of the first aircraft as that of the second aircraft.  If this was the case, the aircraft in the B747 crew's 1 o'clock would have been at FL 250 as reported by them.
2. Reversal of the clock code position.  Where the 1 o'clock position was transposed with the 11 o'clock position. This may have been related to the mental inversion of the radar screen image required to be performed by the controller to give relevant information to the crew of the B747.  The view of the radar screen is north facing, whereas the B747 was heading south and separation had already been achieved between it and the aircraft below. The controller had ensured separation with the aircraft above by requiring the B747 to level out at FL 280.  Giving traffic on this aircraft was a safety measure to assist the B747 crew's situational awareness.

There also appeared to be a misunderstanding of the request from the B747 crew as to clearance to the next waypoint. The controller cleared the B747 to TAPOP when the request was direct to TAXON. This misunderstanding was not considered relevant to this occurrence.

The TCAS display reported by the captain of the B747 was due to the type of TCAS on the aircraft. TCAS II with a 604 software update will display a proximity target if the target is currently within 6 NM and 1,200 ft of the TCAS aircraft.  There was no traffic advisory given by TCAS, but the aircraft was displayed on the screen due to this sensitivity.

SIGNIFICANT FACTOR

Incorrect traffic information was passed to the crew of the B747.