Flight Crew Clearance and Deviation
While en route to Canberra, the flight crew received a tracking clearance from the waypoint AVBEG direct to Canberra Airport and were instructed to leave controlled airspace by descending below the 8,500 ft AMSL controlled airspace base along that track. The crew's normal practice for arrivals was to use a standard arrival route (STAR), and they prepared for the arrival at Canberra using the AVBEG 5A STAR. However, the crew did not request or receive a clearance to descend via the STAR, and with Canberra Approach air traffic control (ATC) services not yet active, this clearance could not have been provided. When the aircraft crossed AVBEG and commenced tracking via the STAR, it deviated from the provided clearance. From AVBEG, the STAR turned south and crossed restricted areas R430A, B and C. The AVBEG 5A STAR included a 10,000 ft AMSL descent limitation until past the waypoint LANYO to ensure that crews using the STAR did not enter the uppermost restricted area. The descent clearance for the direct track provided to the crew did not have a descent restriction, and the controller was unaware that the AVBEG 5A STAR included such a restriction.
Controller Intervention
The controller was required to issue a safety alert as the aircraft's deviation appeared to take it into the active restricted areas. However, the controller had recently taken over management of the airspace and was unsure if the crew were deviating from the cleared route or if a clearance had been provided but not correctly entered in the ATC system. Noting that the aircraft was still 17 NM from the restricted area, the controller intervened by issuing a descent altitude restriction instead of advising the crew of the deviation or issuing a safety alert.
Crew Confusion
The crew believed they were correctly following the AVBEG 5A STAR into non‑controlled airspace. When they received the descent restriction from the controller, they became confused about whether the approach would be conducted within or outside controlled airspace. Despite the controller stating that the approach would take place outside controlled airspace and that clearances were not required for manoeuvring, the crew remained confused and made several clearance requests while operating in non‑controlled airspace. This confusion was resolved only when Canberra Approach and Tower services commenced, and the approach continued using those services.
Contributing Factors
A contributing factor was that the flight crew deviated from the cleared track by commencing the AVBEG 5A STAR. Another contributing factor was that the air traffic controller did not advise the crew of the track deviation or provide a safety alert but provided altitude instructions to maintain separation from a restricted area. This intervention resulted in the aircraft becoming higher than the desired descent profile and the crew becoming confused regarding the airspace classification for the arrival and approach.
Holding Pattern Issue
After the controller's descent clearance following the crossing of the restricted area, the crew did not re‑establish the desired descent profile prior to commencing the approach. The aircraft passed the instrument landing system approach's initial approach fix waypoint MENZI about 680 ft higher than the glideslope. The captain decided to use the approach holding pattern at MOMBI to descend to the desired profile. This decision was made late during the arrival, and the crew did not identify that the holding pattern minimum altitude (5,600 ft) was significantly higher than the waypoint glideslope crossing altitude (4,760 ft).