Socata MSTB20, VH-JTK, Piper PA-44-180, VH-KFO, Adelaide, South Australia, on 17 April 1990

Circumstances:

The PA-44 aircraft was cleared to take-off and given a clearance which included the instructions to maintain runway heading and to call Adelaide Approach airborne. At about the same time, the TB20 was approaching Adelaide at 2,000 feet from Parafield to conduct a practice Adelaide/Parafield non-directional beacon (NDB) approach, which uses the Adelaide NDB. The TB20 pilot was cleared to conduct the NDB approach. The PA-44 did not commence its take-off run until about 110 seconds after lining up and being issued with the clearance. During this period, Adelaide Approach East issued a restriction of 2,000 feet for the PA-44, which Tower passed on to the pilot. Once the PA-44 became airborne, Tower advised Approach East that Tower was able to co-ordinate the separation between both aircraft. Approach East then directed Tower to amend the PA-44 clearance to direct to Port Stanvac at 2,000 feet. Tower could not raise the PA-44 as the pilot had changed to Approach radio frequency as instructed. Approach East then reported that he had issued the revised clearance to the PA-44 pilot. Almost a minute passed before Tower advised Approach East that a conflict was rapidly developing between the PA-44 and the TB20. The TB20 pilot, on the outbound leg of the NDB, reported sighting the PA-44 at a distance of about 30 metres, level, on his right and tracking from right to left.

Significant Factors:

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

1. The PA-44 aircraft held on the ground for almost two minutes before commencing take-off.

2. Both Tower and Approach controllers allowed a situation to develop where neither was certain which section was responsible for separation between the two aircraft.

Recommendations:

1. The CAA might consider this incident as the basis of an article to illustrate to pilots the reasoning behind RAC/OPS-0-52 which states in part that if the pilot calls "ready" he should be prepared to "make a roll-on take-off in one continuous movement if take-off clearance is given". The implication is that the take-off should be commenced without delay and that the Tower controller will assume the aircraft is ready for immediate take-off.

2. The CAA should examine procedures at Adelaide to ensure that there is no doubt which controller is controlling which aircraft. Special attention should be paid to the Adelaide/Parafield NDB procedure and full traffic information should be given to pilots "under the hood" conducting instrument training. The CAA has agreed to prepare an article in response to the first recommendation for publication in the Aviation Safety Digest. The second recommendation was actioned by the CAA during the process of the investigation.