Loss of separation involving a Cessna A150M, VH-KMC and Cessna 150M, VH-MHD, Canberra Airport, Australian Capital Territory, on 21 July 1995

Two Cessna 150s, VH-MHD and VH-KMC, were conducting visual flights from Canberra at the same time. 

VH-MHD was commencing circuits on runway 30 and VH-KMC was departing on a city joy flight from runway 35.  At 1533 (all times are EST) VH-MHD was cleared for take-off from runway 30 with a requirement to maintain runway heading.  At 1535.20 VH-KMC was cleared for take-off from runway 35 and cleared for a left turn after take-off.

At 0535.55 VH-MHD was instructed to make a right circuit, early turn onto crosswind and downwind, traffic to sight is a Cessna heading for the racecourse, airborne off 35 over the old farmhouse.  At 0536.30 VH-MHD was instructed to continue the right turn to the tower and asked do you have that traffic now, it’ll be coming up in your 10 o’clock position. The pilot of VH-MHD responded uh MHD looking, do you want us to turn right now.  VH-MHD was then instructed continue the right turn to track to the tower, that will put you well inside the traffic

At 0536.55 VH-MHD was again asked if the traffic was sighted.  The pilot replied MHD negative.  VH-MHD was then instructed to......tighten the turn thanks, it’s in your 12 o’clock position half a mile continue the right turn now thanks straight to the tower.  At 0536 VH-MHD was advised ... you are clear of that traffic now continue downwind........

Meanwhile, after becoming airborne from runway 35, the pilot of VH-KMC contacted Canberra Departures Control at 1536.42 and advised .......KMC in a left turn on climb to 4000 left 2500.  VH-KMC had not been given any traffic advice by Canberra Tower on VH-MHD and there had been no coordination with Canberra Departures Control to pass any traffic advice.

At 1537.08 the pilot of VH-KMC advised departures we seem to have an aeroplane in the circuit area still heading towards us, do you have anything on it.  Departures advised VH-KMC of traffic in his 12 o’clock position and to maintain separation with that traffic.  VH-KMC then advised he’s just passed over me at about a 100ft.

When the aerodrome controller instructed VH-MHD to make a right circuit off runway 30 this put the aircraft in the same quadrant of airspace as VH-KMC making a left turn off runway 35.  The controller thought that instructing VH-MHD to tighten the right turn would resolve any potential conflict.  However, VH-KMC turned left earlier than expected whereas VH-MHD turned right later than expected.  The controller continued to give traffic to VH-MHD and instructed the pilot to track towards the tower but at no time passed traffic to VH-KMC nor instructed VH-KMC to remain on tower frequency.  The pilot of VH-MHD never sighted VH-KMC.

The traffic information passed to VH-MHD may not have been sufficient for the pilot to sight VH-KMC as it pre-supposed that the pilot was familiar with local landmarks and no relative height was passed. Additionally, the controller did not think it was significant that the pilot of VH-MHD may have had difficulty seeing VH-KMC in that he was flying a high wing aircraft, in a right turn, with the traffic approaching from his four to five o’clock position.

When it became apparent that VH-MHD could not sight VH-KMC and was not tracking towards the tower, the controller failed to issue a positive control instruction to VH-MHD, such as turn right immediately, to ensure that separation was maintained between the two aircraft.

An examination of the recorded radar data for Canberra terminal area indicated no apparent traffic reason why VH-MHD was instructed to make a right circuit.  The controller advised that he thought there was inbound traffic which may have conflicted if VH-MHD flew a left circuit.  At the time of the occurrence the aerodrome controller was under a moderate workload.  There were two aircraft operating in the circuit, VH-KMC departing on a scenic flight and a BA146 on final for runway 35.

Significant Factors

The following factors were considered relevant to the development of the incident:

1. The aerodrome controller placed two VFR aircraft in the same small quadrant of airspace and on different radiofrequencies, when an alternative was available.
2. The aerodrome controller did not pass mutual, timely and effective traffic information.
3. The aerodrome controller did not take positive steps to ensure separation.
4. The pilot of VH-MHD was slow in complying with an instruction to make a right turn.
5. The pilot of VH-KMC made an earlier than expected left turn.