Separation issue

On 16 November 2014, a Robinson R44 helicopter, registered VH-YDK (YDK), was approaching Jandakot Airport on a charter flight from Rottnest Island, Western Australia, with a pilot and three passengers on board. At about 1348 Western Standard Time, the pilot of YDK reported downwind for runway 24 on the Jandakot Tower frequency.

At about the same time, the pilot of a Bell 412 helicopter, registered VH-EWA (EWA), prepared to conduct a rescue flight to Bunbury, Western Australia, with a crewman and paramedic on board. As YDK turned onto final, at about 400 ft above ground level (AGL), the pilot of YDK sighted EWA outside its hangar and elected to continue the approach.

At about 1350, the pilot of EWA requested to taxi to the compass swing bay on the Ground frequency. As the pilot commenced taxiing, the crewman sighted YDK at about 150 ft AGL and on an approach towards EWA. He directed the pilot of EWA to go forward.

At about 1350, the pilot of YDK broadcast on the Tower frequency: ‘YDK just out your left hand window’. The pilot of EWA was monitoring the Ground frequency and did not hear that call. YDK then descended and passed behind EWA towards a landing on the middle of the grassed area.

The pilot of EWA continued to taxi towards the compass swing bay, and when approaching the bay, first sighted YDK which was then passing behind EWA and about 30 m away.

The environment and procedures in the helicopter precinct at Jandakot require that pilots make the mandatory radio calls, maintain a good lookout and taxi, depart and approach the area by the most predictable routes to assist others in sighting them.

Aviation Short Investigations Bulletin - Issue 39

A DeHavilland Canada DHC-8 (Dash 8) had been cleared to take-off on runway 30, with a request to make an early right turn to track to Point Lookout. The aircraft was rolling when the crew heard traffic information being issued by the aerodrome controller to an inbound formation of three McDonnell Douglas F-18A (Hornet) fighter aircraft. The Dash 8 crew also heard the controller advise the formation pilots that an early "pitch" (a 180 degree turn onto downwind) was available. The Dash 8 crew subsequently commenced a right turn at about 350 ft. At an altitude of about 700 ft they saw a Hornet to their right, passing from left to right about 300 ft higher than them.

The Dash 8 crew arrested their rate of climb as the Hornet passed over them and was lost from view. It was subsequently determined that the Hornet pilots had sighted the Dash 8 prior to entering the circuit at 1,500 ft. The first two aircraft were able to "pitch" early, passing behind the Dash 8. The third Hornet commenced to "pitch" just astern of the Dash 8 but overtook that aircraft during the turn. The Hornet pilot assessed that the Dash 8 was at approximately 700 ft, with a moderate rate of climb, and that adequate vertical separation would be maintained. The aerodrome controller did not use separation assurance techniques to establish separation between the departing Dash 8 and the arriving fighters. As a result, separation became reliant on the judgement of the Hornet pilots, rather than by the use of air traffic control traffic conflict strategies.

The aircraft departed two minutes apart from Kalgoorlie enroute to Perth. The first aircraft, BAe 146 VH-NJZ, was cleared by the sector air traffic controller to track via Southern Cross on planned route climbing to FL240. The route followed the 255 degree radial from the Kalgoorlie VOR. When the pilot of the second aircraft, Boeing 737 VH-CZP, contacted the sector controller for a clearance, he advised that the aircraft was avoiding weather and tracking the 240 degree radial from Kalgoorlie VOR. The sector controller subsequently cleared CZP to track via the Nalar Dulya route on climb to FL350.

The pilot of CZP was communicating with the pilot of NJZ on the flight service frequency to ensure separation was maintained between the aircraft during the weather avoidance. The FSO reported to the sector controller that the pilot of CZP advised that he was initially tracking outbound on the 257 degree radial from the Kalgoorlie VOR and was now paralleling track. When queried by the sector controller, the pilot of CZP advised that the aircraft was on approximately the 246 degree radial from the Kalgoorlie VOR and was leaving FL210 on climb. The controller instructed the pilot of CZP to maintain FL210, to which the pilot replied that the aircraft was leaving FL220 on descent to FL210. The pilot of NJZ was immediately queried by the sector controller about his altitude and he reported that his aircraft was leaving FL225 on climb.

The investigation revealed that it was unlikely that a breakdown in separation occurred because the pilots appeared aware of their relative positions and maintained separation. However, the sector controller took action to ensure procedural separation was maintained based upon the information available to him.

The pilot of VH-SKN reported that, while cruising FL170 some 52NM from Boulia, a VFR aircraft (VH-FDM) reported 49NM from Boulia, on the same track, leaving FL175 on descent. SKN had been advised of several IFR aircraft by Flight Service but had not received any broadcasts from VFR traffic until the descent call from FDM. The pilot of SKN considered that the three mile separation which existed between his aircraft and FDM compromised safety.

FDM departed Mt Isa 5-10 minutes before SKN and thus should have been aware that SKN was tracking for Boulia. Both aircraft were King-Air variants, but had a significant performance margin over FDM and it was this which contributed to SKN catching up to FDM during the flight.

An aircraft was approaching to land through a straight-in approach in accordance with the published procedures and criteria. At about 2 NM on final approach, another aircraft reported on base. Although an attempt to contact the aircraft on base by radio was made, it continued and joined final about 500 m in front of the aircraft conducting the straight-in approach. The pilot flying the straight-in approach conducted a go-around and landed off a normal circuit.

The pilot reported that at 25 DME inbound to Tennant Creek, the appropriate inbound call was made on the CTAF frequency. No traffic responded to this call, nor were any other calls heard until, approaching 5,000 feet, there was an excited call from an unidentified aircraft to "aircraft inbound to Tennant Creek". VH-ANY levelled at 4,500 feet and called the other aircraft. The pilot of VH-NLB responded, saying that he had left 5,000 feet on climb. VH-ANY then continued descent to Tennant Creek.

The pilot of VH-NLB later said that he had made taxy, airborne and departure calls on departing Tennant Creek. He estimated the minimum separation with VH-ANY to have been about 1NM. The crew of VH-ANY did not see the other aircraft.

When approaching the aerodrome, the crew made the appropriate CTAF calls, with no response. At 1,500 ft, just before turning crosswind, a single engined Cessna aircraft was observed about 800 m to the right and about 200 ft below. No response was heard after further calls on CTAF. The crew was unable to identify the aircraft.

The pilot suggested that the Hervey Bay / Maryborough area be made an MBZ due to the number of airline flights into the area each day, and the traffic density associated with the two aerodromes.

Advice of a safety deficiency has been raised and is being considered. The situation is common to other aerodromes subject to frequent airline operations.

The BAe146 was inbound to Kununurra from Curtin and the crew had been listening on both the area and the MBZ frequencies. They heard the pilot of the C207 make contact with Perth and discuss SARTIME arrangements and give his destination as Broome. This information indicated the C207 might be conflicting traffic for their arrival. They assumed the C207 was still on the ground at that time. As nothing further was heard from the pilot of the C207, the crew of the BAe146 made several attempts to contact him. When contact was established the C207 was 12 NM from Kununurra on the 242-degree radial at 5,500 ft. The BAe146 was 14 NM from Kununurra on the 250-degree radial at 3,800 ft, on descent.

The pilot of the C207 reported that his aircraft was fitted with one VHF set. After making his departure report on the MBZ frequency he changed to the area frequency and became engaged in a discussion with Perth flight service about his SARTIME. The discussion took longer than expected and during that time he could not hear any transmissions from the BAe146 on the MBZ frequency. When he changed back to the MBZ frequency he heard the transmission from the BAe146, and he answered immediately. He had tracked south of the Kununurra - Broome track to remain clear of cloud. He does not believe he came close to the BAe146.

It is likely that the discussion between the pilot of the C207 and Perth flight service, which the crew of the BAe146 assumed had taken place whilst the C207 was still on the ground, was the one that occurred after the C207 had departed. Consequently, the BAe146 crew did not hear the taxi and departure transmissions that preceded that discussion. The fitment of only one VHF set prevented the pilot of the C207 from adequately monitoring the MBZ frequency and, as a result, separation between the two aircraft could not be arranged in a timely fashion.

Details of the flight were forwarded to Bankstown Tower, and both Sydney and Brisbane Air Traffic Control centres.  As the plan was considered to be for the following day, it was held at the Aviation Data System Operators' desks in the two centres, and flight progress strips were not issued to the appropriate sector controllers. 

Consequently, when the crew requested a clearance there was a delay of about 40 minutes to the planned departure as time was spent locating the plan and flight progress strips.  Due to this delay, the crew elected to depart visually from Bankstown, via the lane of entry at 2,000 ft, outside controlled airspace.

The Bankstown tower coordinator controller notified Sydney Flight Service of the aircraft callsign, time of departure, tracking details and altitude.  As the flight had been originally planned to remain within controlled airspace, this was the first time that the Flight Service officer was provided with information about the Citation. The officer annotated a flight progress strip for the aircraft with the details provided.

The crew of a Twin Otter reported departure from Aeropelican aerodrome and indicated that the aircraft was tracking 215 degrees M, on climb to 6,000 ft. The Flight Service officer did not pass mutual traffic information to the crews of the Citation or Twin Otter, as the nominated altitudes of the aircraft provided vertical separation and ensured the aircraft were not in conflict.  When the Citation was north of the lane of entry, the pilot in command initiated a climb outside controlled airspace, anticipating that a clearance would become available which would allow the aircraft to continue climbing to the planned level of Flight Level 330. Recorded radio communications indicated that the Citation crew did not report climbing above 2,000 ft.

Shortly after the Twin Otter departed Aeropelican, the Flight Service officer handed over duty to another officer, a process which took about two minutes to complete.  The new officer then became engaged in coordinating clearances into controlled airspace for the Citation and another aircraft, and responding to a number of calls from other aircraft in the officer's area of responsibility. The Citation was then instructed to contact Brisbane centre for a clearance. Just after the pilot transferred to the Brisbane frequency, the Flight Service officer was advised by the Sydney Departures radar controller that the aircraft had passed in close proximity to the Twin Otter, while outside controlled airspace. Neither crew were aware of the proximity of the other aircrft.

The Flight Service officer handing over was expecting the pilot of the Citation to receive a clearance with little delay. His impression was that the aircraft would soon enter controlled airspace and would therefore remain in his area of responsibility for only a short period. Consequently, he did not request additional tracking information on the Citation such as the next position and estimated time interval. As a result, the Flight Service officer assuming responsibility for the area had limited information to assist in resolving the conflict. The situation was further compounded by the high speed of the Citation, in comparison to other general aviation aircraft, and the rate of closure with the Twin Otter. As the new officer became distracted by other coordination tasks there was insufficient time to appreciate the lack of positional information on the flight progress strip. Without that information the officer was unable to establish if a traffic conflict was likely to occur.

The Flight Service officer may have been assisted in identifying a conflict if the departure report for the Citation, provided by the Bankstown tower coordinator controller, included details regarding the next reporting point and estimated time interval. Current procedures require Bankstown tower controllers to notify only those details which were provided in this occurrence.

The absence of a report by the crew of the Citation, advising that the aircraft had left 2,000 ft and was climbing, was an important cue not received by the Flight Service officer. Without this cue, the officer continued to assume that the Citation and Twin Otter were vertically separated and not in potential conflict. Consequently, traffic information was not provided to the crews of either aircraft.

Safety Action

The Bureau is researching safety issues highlighted during the course of this investigation concerning aspects of Air Traffic Control coordination.  Any recommendations and responses will be published in the Bureau's Quarterly Safety Deficiency Report.

"As a result of these reports, the Authority requested Airservices to issue a NOTAM on 27 October 1995 to correct the position of the chart symbol depicting this operation, which is incorrect on the Brisbane VTC but correct on the Oakey VTC (both dated 7 December 1995).

"In discussion with the operator it appears that, despite his making the required broadcasts prior to parachutists exiting the drop aeroplane other traffic in the area are not responding to those broadcasts and therefore parachutists are not aware of traffic which will pass below them whilst they are still under canopy some five minutes later. This traffic may be up to 15 miles from the drop zone at the time the drop aircraft broadcasts its advisory message and may not recognise the potential for confliction.

"A further difficulty is that the drop zone is only four miles from the frequency change point which coincides with the Amberley CTR boundary, and so broadcasts are often made on both frequencies. As an additional precaution, the target control officer on the drop zone monitors traffic on a portable VHF transceiver.

"The operator has previously sought the advice of the Queensland RAPAC on the establishment of a formal danger area to provide an enhanced warning to itinerant aircraft of the extent of the hazard posed by their overflying this area. However, the Authority is not convinced that a danger area is necessary in this case.

"Nevertheless, since airspace is now the responsibility of Airservices Australia, your report and recommendation have been passed to them for consideration.

"The questions of re-issuing a safety poster about parachuting activity and publishing an article on ways to minimise risks when flying near a parachute drop zone, have been raised with the Authority's Safety Promotion Section and some further educational material is under consideration."

The following response was received from Airservices Australia on 6 May 1996.

"Subject: BASI IR950225 Gatton

"Reference incorrect location of parachute symbol;

A NOTAM was issued alerting pilots to the parachute symbol location. The symbol appears on the 20 June 1996 charts at the amended position.

"The proposal for a Danger area was referred to the Queensland Regional Air Co-ordinating Sub Committee (RACS) for consideration.

"As part of the "Process 5 for the Origination, Co-ordination, Ratification, Promulgation and Registration of Airspace and Air route Amendment Proposals " the recommendation was considered by the Queensland Regional Airspace Users Advisory Council (RAPAC).

"The RAPAC did not support the establishment of a Danger area. Further action regarding chart symbols, pilot education and consultation with CASA is to be undertaken by the RACS."

The Bureau of Air Safety Investigation has classified these responses as: CLOSED - PARTIALLY ACCEPTED.