Loss of separation

What happened

At about 1117 Eastern Standard Time on 29 August 2020, a Piper PA-28 departed Bankstown Airport, New South Wales (NSW) for a private flight, tracking to Bathurst, NSW under the visual flight rules. After departure, the pilot of the PA-28 commenced a shallow climb with the intention of remaining clear of the Sydney control area steps. However, at approximately 26 NM west of Sydney, the pilot inadvertently entered controlled airspace without a clearance.

A short distance ahead and above the PA-28, a Cirrus SR20 was on a private flight from Bankstown Airport, NSW to Dubbo Airport, NSW under the instrument flight rules. The SR20 was on climb to 6,000 ft in class C airspace when the aircraft’s traffic advisory system alerted the pilot to the presence of the PA-28. The traffic advisory system indicated the PA-28 was climbing towards the aircraft in the 6 o’clock position relative to the SR20. The positioning of the two aircraft prevented the SR20 pilot from sighting the PA-28. The SR20 pilot queried the proximity of the PA-28 with Air Traffic Control (ATC). ATC then identified the conflict and issued a safety alert to the SR20.

At about 1127 EST, the SR20 and PA-28 came into close proximity, with separation between the two aircraft reduced to 0.8 NM laterally and 300 ft vertically. ATC made a broadcast to the unverified PA-28 informing the pilot of the airspace infringement and issuing turn instructions to regain separation. The PA-28 was observed by ATC to follow the separation instructions and commence a turn to the left. The conflict was subsequently resolved, and the PA-28 exited controlled airspace.

Safety message

This incident highlights the importance of maintaining navigational accuracy and traffic awareness when operating in close proximity to control area steps. It also illustrates the value of enhanced situational awareness provided by airborne traffic advisory systems such as that fitted to the involved Cirrus SR20.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

What happened

On the 4 October 2019, an Agusta A109S helicopter was on approach to Sydney Airport, New South Wales. During approach, air traffic control (ATC) issued the pilot a clearance to track from the clearance limit to overhead the threshold runway 07. The pilot read back, ‘from the clearance limit track overhead the 07 threshold’. The pilot reported to the ATSB that he believed he was cleared to track overhead the 07 threshold (for the heliport).

A Boeing 737 waiting on the crossing runway for an intersection departure was provided with the helicopter traffic and advised ATC that the helicopter was in sight. ATC subsequently issued the take-off clearance.

ATC then advised the helicopter pilot that the clearance limit was the runway 07 threshold and passed traffic on the 737, however the transmission was blocked.

As the 737 began its take-off, ATC observed the helicopter continue past the runway 07 threshold and immediately issued instructions to the helicopter to expedite through the runway intersection.

Safety action

As a result of this occurrence, Airservices Australia advised the ATSB that they are taking the following safety action:

The air traffic controller will be counselled on the appropriate phraseology when issuing a clearance limit.

Safety message

This incident shows the effectiveness of the conflict resolution training received by ATC to resolve loss of separation events resulting from radio transmission errors or miscommunication between controllers and flight crew.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

What happened

On 4 March 2018, a Bombardier DHC-8 (DHC-8) departed Mildura Airport, Victoria (Vic.), for Melbourne Airport, Vic. During climb, the flight crew requested clearance to climb to FL 250^[1] and were approved by ATC to climb to FL 240.

A Boeing 737 (737) was en route from Adelaide Airport, South Australia (SA), to Sydney Airport, New South Wales (NSW), maintaining FL 250 on a crossing track.

At 1744 Eastern Standard Time (EST), ATC cleared the DHC-8 to climb from FL 240 to FL 250 resulting in a loss of separation with the 737. ATC subsequently received a short-term conflict alert (STCA). ATC instructed the crew of the DHC-8 to maintain FL 240 but as the DHC-8 was already climbing through FL 245, ATC instructed the crew to descend and turn left onto heading 090. They then instructed the crew of the 737 to turn right immediately onto heading 180 for separation. Once the separation standard was regained, the DHC-8 was cleared to climb to FL 250 and both aircraft continued without incident.

Separation reduced to 900 ft between the aircraft when they were 5 NM apart. Neither flight crew received a TCAS resolution alert (RA).

Safety message

This incident shows the effectiveness of the ATC short term conflict alert (STCA) system and conflict resolution training received by ATC for loss of separation events. It also highlights the importance of flight crews responding immediately to ATC instructions.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Flight level: at altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 250 equates to 25,000 ft.