Aviation safety investigations & reports

Piper Aircraft Corp PA-28-181, VH-MIZ

Investigation number:
Status: Completed
Investigation completed


The pilot of a piper Archer was cleared for final by the Terminal Area (TMA) controller for a practice runway 35 Instrument Landing System (ILS) approach at Canberra. The duty runways at Canberra were 17 and 12. A Saab 340, VH-KDQ, had recently departed from Canberra using runway 17 when the Canberra surface movement controller (SMC) recognised that it was tracking in the opposite direction towards the Archer which was on final approach. The TMA controller took action to resolve the situation by instructing the pilot of the Archer to turn away from the ILS approach. The Archer was at about 8 NM on final approach at 4,500ft while KDQ was 2 NM upwind leaving 3,000ft on climb. The Canberra aerodrome controller (ADC) dept KDQ on frequency until he observed on radar that the Arhcer was turning and then instructed the crew of KDQ to contact the TMA controller.

The separation standard required between aircraft was either 3 NM laterally or 1,000ft vertically. Examination of recorded radar data indicated that the distance between the aircraft was about 4 NM laterally and 1,100ft vertically at the closest point of approach. There was no infringement of separation standards.

The TMA controller had moved the electronic flight strip for the Archer into the traffic management window of The Australian Advanced Air Traffic System (TAAATS) display, indicating that the aircraft was to carry out the ILS approach. The movement of the electronic strip into the traffic management window automatically indicated the pending arrival of the aircraft to the ADC in Canberra Tower. The ADC annotated the electronic strip with a "back-slash", which indicated an acknowledgment of the pending transfer.

Six aircraft had been issued airways clearances for departure from Canberra. The TMA controller was aware of the pending departures but he was not aware of when they would be ready for take-off. Two of those aircraft, Impulse 935 and VH-KJQ, subsequently taxied and the ADC advised the TMA controller that he was releasing those aircraft. Auto release procedures, which were in operation at the time, authorised the ADC to clear aircraft for take-off on pre-determinded departure tracks after advising the TMA controller of the pending release. Auto release procedures were designed to minimise voice coordination between the TMA controller and ADC. Under auto release procedures, dependence was placed on the ADC to ensure that there was sufficient spacing between successive departing aircraft to enable the TMA controller to establish and maintain the required separation standard. The ADC advised the TMA controller that the Archer could "have the ILS" after those two aircraft, while also reiterating that there were a number of additional pending departures.

By the time KJQ had become airborne, a further three aircraft had taxied for departure: Eastern 832, Impulse 917 and KDQ. The ADC advised the TMA controller that two of the aircraft were approaching the holding point and one was just leaving the parking apron. The ADC also instructed the TMA controller to "hold [the Archer] out". The TMA controller did not acknowledge that instruction nor did the ADC seek acknowledgment. The ADC subsequently advised the TMA controller that he was releasing "Eastern 832 followed by Impulse 917 then KDQ". The TMA controller replied "Roger".

The TMA controller was required to annotate his electronic flight strip with an "A" for each aircraft to signify that auto-release coordination had been carried out. After receiving the coordination on the latter three aircraft, the TMA controller did not immediately annotate his electronic strips. Rather he advised the pilot of the Archer of a further delay and provided radar vectors for re-sequencing. When he did annotate the electronic strips with an "A", he only annotated Eastern 832 and Impulse 917. The controller stated later that he might have omitted to annotate the electronic strip for KDQ by confusing that aircraft with KJQ, the crew of which had just called the controller with a departure report.

The TMA controller then vectored the Archer to carry out the ILS approach after the departure of Impulse 917. After that crew had contacted the TMA controller, the pilot of the Archer was cleared for final for the ILS approach. By the time KDQ became airborne, a further two aircraft had taxied and the ADC coordinated their release with the TMA controller. The TMA controller queried that they would be "after" the Archer, to which the ADC replied "no they're RPT [Regular Public Transport] they've got higher priority they are going".

The ADC and TMA controllers then entered into a discussion about the situation that lasted about 26 seconds. During that period neither controller seemed to understand where the aircraft under the other person's control was in relation to the aircraft under their control. It was not until a third party, the Canberra SMC, intervened that the controllers understood there was a potential conflict situation and the TMA controller then took action to resolve the situation.

Auto-release procedures

Canberra Local Instructions stated that prior to issuing a take-off clearance, the ADC "shall advise the TMA controller of the pending release and receive an acknowledgment by callsign". During this occurrence, the ADC released five aircraft: none were acknowledged by callsign nor were callsign acknowledgments sought.

Voice coordination - arriving aircraft

Movement of the electronic flight strip into the traffic management window and acknowledgment of the sequence by annotating the strip with a back-slash was normally the only coordination required between the TMA and the ADC for an arriving aircraft. Canberra Local Instructions stated that, in addition to the use of the traffic management strip, the TMA controller "shall voice coordinate when:

a) An instrument approach other than a straight-in approach to the system arrival runway will be conducted."

Further, Canberra Local Instructions stated that use of the reciprocal runway directions may be approved for individual aircraft:

"a) when an aircraft is conducting a practice instrument approach and missed approach subject to mutual agreement between TMA and CBA [ADC]".

From the time the Archer was turned away from the ILS apprach on the first occasion there was no mutual agreement between the controllers for the use of the reciprocal runway and there was no voice coordination regarding the subsequent approach for the aircraft.

Traffic Management

The Archer pilot contacted the Melbourne Senior Terminal Area Controller (STAC) to book a training ILS approach at Canberra. The booking system established an order of priority for flight crews competing for training ILS approaches. It was reported that it would be unusual for the STAC to deny an ILS booking. It was mainly a paperwork exercise and there were no known busy times blocked out on the booking sheet. In this particular instance there was no coordination between the FMA staff and Canberra tower staff regarding the suitability of the timing of the training ILS approach for the Archer, despite seven pending departures from the reciprocal runway around the same time.

Organisational Issues

The Canberra TMA controllers were originally co-located with the aerodrome function in Canberra. During that time controllers were rotated through both TMA and aerodrome elements. In 1994, the TMA element was relocated to Melbourne. The controllers involved in this occurrence had 5.5 and 7 years experience respectively in their positions at Canberra Tower and in Melbourne. During that time, both had two familiarisation visits to each other's unit. In both cases, one visit was prior to the transition to TAAATS and one was as part of the transition process. Neither controller believed that the frequency of these visits was sufficient to maintain an appropriate level of awareness and appreciation of the other person's working environment.


The Archer was allowed to depart from Canberra to undertake two training ILS appraches when up to seven Regular Public Transport departures were pending from the reciprocal runway. While the ILS booking system was not intended as a traffic management tool, use of the system for that purpose may have assisted in planning the traffic situation more effectively.

While the Archer was being vectored for the ILS approach, coordination took place between the ADC and the TMA controller for two departures and then, by mutual agreement, for the Archer to conduct the first training ILS approach. The TMA controller was subsequently advised that a further three aircraft were taxiing that had priority and to hold the Archer out. There was no further discussion between the controllers as to when the Archer would be re-sequenced for the ILS approach. From that point in time there was no mutual agreement between the controllers for the use of the reciprocal runway. Moreover, no voice coordination regarding the Archer, as required by local instructions, took place subsequent to the first occasion when mutual agreement had been achieved.

The readback of a callsign as part of the acknowledgment of any coordination is an important defensive measure that helps minimise the likelihood of any misunderstanding between controllers. In this incident, there was no acknowledgment by callsign from the TMA controller during the auto release coordination and the ADC sought notice. Use of the correct acknowledgment and/or a challenge from the ADC to obtain the correct acknowledgment would have likely reiterated that KDQ was in the group of aircraft about to be released, thereby ensuring that the TMA controller had an accurate understanding of the developing traffic situation.

Once the confliction between the two aircraft developed, valuable time was wasted by both controllers discussing the situation, rather than resolving the problem. It was fortunate that the SMC controller had an awareness of the traffic situation and chose to intervene, thereby, prompting action to resolve the confliction before separation standards were infringed.

Significant Factors

  1. The TMA controller and the ADC did not mutally agree on the use of the reciprocal runway for a training ILS apprach after the traffic sequence was changed.
  2. The TMA controller and the ADC did not use voice coordination to revise the sequencing of the Archer
  3. The TMA controller did not use aircraft callsigns as an acknowledgment of auto-release coordination.
  4. The ADC did not seek an acknowledgment using callsigns from the FMA controller during auto-release coordination

Safety Action

Local safety action

Airservices Australia has amended Local Instructions to more clearly indicate the responsibility of the ADC to ensure that, prior to issuing a take-off clearance, the callsign of an aircraft is read back by the TMA controller as part of the acknowledgment of the auto release coordination.

Local Instructions have also been amended to ensure voice coordination between the TMA controller and the ADC is more specific when clearing an aircraft for an instrument approach to other than the system runway. Specifically, revised instructions require that voice coordination take place "immediately prior to the aircraft being cleared for final".

Airservices Australia Advised the ATSB that it is:

a. taking advantage of opportunities that arise from time to time to provide controllers with familarisation visits, but that a formalised familiarisation program was not currently possible.

b. reviewing the arrangements for booking training instrument approaches at Canberra.

General details
Date: 05 March 2001   Investigation status: Completed  
Time: 1437 hours ESuT    
Location   (show map): 2 km S Canberra, Aero.    
State: Australian Capital Territory   Occurrence type: Breakdown of co-ordination  
Release date: 05 February 2002   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer Piper Aircraft Corp  
Aircraft model PA-28  
Aircraft registration VH-MIZ  
Serial number 28-7790276  
Type of operation Flying Training  
Damage to aircraft Nil  
Departure point Canberra, ACT  
Destination Canberra, ACT  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer S.A.A.B. Aircraft Co  
Aircraft model 340  
Aircraft registration VH-KDQ  
Serial number 340B-325  
Type of operation Air Transport Low Capacity  
Damage to aircraft Nil  
Departure point Canberra, ACT  
Destination Sydney, NSW  
Last update 13 May 2014