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The aircraft was cleared to climb to Flight Level (FL) 390. After departure, and when on Brisbane Approach (South) frequency, the pilot requested FL 370. This was approved and co-ordinated by the Approach (South) controller with the Brisbane Sector 1 Radar controller. Prior to this, the Sector 1 Procedural controller had co-ordinated the original level clearance for the aircraft with the Brisbane Sector 2 Procedural controller as FL 390. The Sector 1 Radar controller annotated FL 370 on the flight strip. Normally, the Sector 1 Procedural controller would then have co-ordinated this change with the Sector 2 Procedural controller. However, this was not done and was not detected by the Sector 1 Radar controller. He later handed off the aircraft to the Sector 2 Radar controller without reference to the level. (This is the correct procedure when the current level assigned has been co-ordinated procedurally.) The aircraft was transferred to Sector 2 and reported on climb to FL 370 to the Sector 2 Radar controller. However, the discrepancy with the co-ordinated level was not detected and when control of the aircraft was transferred to Sydney Sector 2 the level was co-ordinated as on climb to FL 390. Later, while the aircraft was still in the Brisbane FIR, the Sydney Sector 2 Radar controller noticed that the aircraft was maintaining FL 370. This was queried with Brisbane and the oversight was discovered. An examination of the voice tape recording showed that when the aircraft called Sector 2 reporting on climb to FL 370, the Sydney Sector 2 Radar controller was coordinating a handoff to the Brisbane Sector 2 Radar controller and the two transmissions over-ran. This made the transmission from the aircraft difficult to hear clearly. However, the Brisbane Sector 2 Radar controller did not confirm the level from the aircraft, but assumed it to be FL 390 as that was the level shown on the flight strip. The Sector 1 Radar controller, after writing FL 370 on the flight strip, did not follow this up with any coordination checks as was standard procedure. The controller indicated that an aspect relating to the control of a military aircraft was on his mind around the time of the omission. This may have been a level of distraction sufficient to cause the omission. SIGNIFICANT FACTORS: 1. The Sector 1 Radar controller failed to pass a change of level to the next sector, possibly because he was distracted. 2. The Sector 2 Radar controller failed to confirm the aircraft's level. SAFETY ACTION: On 19 August 1993, an instruction was issued by the Manager Brisbane AACC amending the procedural requirements so that controllers are now required to provide an adjacent unit or position with advice of an amended level whilst affecting handover. In response to this, and other recent incidents in this area, the Bureau of Air Safety Investigation, in co-operation with the Civil Aviation Authority, have conducted further investigations, resulting in the publication of BASI Investigation Report BS/930154 titled, "An Investigation Of Systemic Factors Underlying Air Safety Occurrences In The Brisbane Area Approach Control Centre."
General details
Date: 15 August 1993 Investigation status: Completed 
Time: 9:11 EST  
 Investigation type: Occurrence Investigation 
 Occurrence type: Breakdown of co-ordination 
Release date: 05 April 1994 Occurrence class: Airspace 
Report status: Final Occurrence category: Incident 
Aircraft details
Aircraft manufacturer: Airbus 
Aircraft model: A320-211 
Aircraft registration: VH-HYF 
Sector: Jet 
Damage to aircraft: Nil 
Departure point:Brisbane Qld
Destination:Sydney NSW
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Last update 23 July 2015