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Analysis

Summary

Throughout this analysis it should be noted that the pilots of both aircraft and the ATS controller involved in the occurrence complied with the rules and procedures for operation in Class E airspace associated with the NAS phase 2b, implemented on 27 November 2003.

The regulations, procedures and educational material associated with that implementation stated that there was a shared responsibility by pilots of IFR and VFR flights to see-and-avoid each other in Class E airspace.

Prior to the implementation of NAS phase 2b on 27 November 2003, both aircraft involved in this occurrence would have been operating in Class C airspace. As such, they would have been subject to an ATS airways clearance and would have been provided with separation in accordance with Class C airspace rules and procedures. In order for two aircraft to pass in close proximity at these flight levels in Class C airspace, those rules and procedures would need to have been compromised. As the pilots of both aircraft and the ATS controller complied with the rules and procedures for Class E airspace under NAS, those rules and procedures do not preclude an IFR high performance, high capacity regular public transport aircraft from passing within such close proximity as to generate a TCAS RA on either known or unknown VFR traffic.

The controller's relatively low workload and other factors, such as the Lancair pilot submitting flight notification details, and broadcasting his departure from Maroochydore, assisted the ATS controller to detect a possible conflict. Although there was no requirement for the controller to pass traffic information to the pilot of the Lancair about the location of the 737 under NAS Class E airspace procedures, the controller provided traffic information to both aircraft with respect to each other.

Part 5 of MATS also stated that controllers shall issue a safety alert when, in the consideration of the controller, such an advice was warranted to avoid conflict. In the circumstances of this occurrence, the controller had provided traffic information to the crews of both aircraft, and the Lancair pilot had broadcast that he had the 737 in sight. Accordingly, the onus was then on the Lancair pilot to avoid the 737. In those circumstances, the provision of a safety alert, which may have included a suggested course of action, may also have complicated the situation, if that suggestion was contrary to what the pilots of each aircraft considered necessary.

Provision of a safety alert, in the circumstances of this occurrence, was not required. However, MATS did not provide any guidance to controllers on the circumstances under which the provision of a safety alert would be appropriate. Publication of those guidelines may assist controllers to determine when a safety alert should be issued.

In Class E airspace, the provisions of CAR 163A required the crews of both aircraft to 'see, and avoid' each other. The 737 crew were unable to see the Lancair despite their attempts to do so. The Lancair pilot reported that he had the 737 in sight. When the 737 crew observed the position of the Lancair on the TCAS navigation display, they commenced action to avoid a confliction prior to receipt of both the TCAS TA and RA. In concert with that action, they continued in their attempts to visually acquire the Lancair, in accordance with Class E airspace see-and-avoid requirements.

In the circumstances of this occurrence:

  • the ATS controller took more actions than those required by the published requirements for Class E airspace and MATS;
  • the Lancair pilot took more actions than those required by the published procedures for Class E airspace under NAS;
  • the early action taken by the 737 crew to avoid the conflict was not contrary to the published procedures for Class E airspace under NAS.

Despite those actions, the two aircraft came into such proximity that a TCAS RA was generated in the 737.

Both aircraft were operating in Class E airspace that was introduced as part of the National Airspace System (NAS) phase 2b on 27 November 2003. (An ATSB research report titled National Airspace System Stage 2b: Analysis of Available Data was released in July 2004.) As no prescribed separation standards are applicable in these circumstances, there was no infringement of separation standards. However, ATS audio tapes, radar and TCAS data, and information obtained from the air traffic controller and the pilots of both aircraft were consistent and indicate that the aircraft came into such close proximity that a threat to the safety of the aircraft may have existed. Therefore, the incident has been classified by the ATSB as an airprox event.

The incident at Canty IFR reporting point, on 3 December 2003 (ATSB report 200304963) was also classified as an airprox event.

Unlike this incident north of Brisbane on 7 April 2004 and the Canty incident, the occurrence near Launceston on 24 December 2003 (ATSB report 200305235) was classified as a serious incident due to the lack of radar coverage in the Launceston area and the absence of radio broadcasts from the pilot of the Tobago, which created an unalerted see-and-avoid environment for the crew of the Boeing 737. The air traffic controller also was unaware of the Tobago.

 
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