When VH-DLF was descending through 7,500 feet, 65 km from Adelaide, Adelaide Departures advised the pilot of an unidentified aircraft converging from his right. Departures continued to update the pilot of VH-DLF on the position of the other aircraft (which he was unable to sight, probably due to haze and the position of the setting sun) but were unable to advise the altitude of the other aircraft. A short time later the pilot of VH-DLF observed a Piper Pawnee aircraft, with a glider in tow, pass about 200 ft overhead.
At the time VH-DLF was descending through 6,300 ft. The pilot advised Departures of the near collision, and Departures confirmed that his aircraft was in controlled airspace. Attempts to contact the tug and glider by radio were unsuccessful. Subsequent investigation revealed that VH-IGR, a Piper Pawnee, had towed a glider (VH-IKO), cruising at about 6,500 ft, from Port Pirie to Murray Bridge at about that time. The lower limit of controlled airspace on their track was 4,000 feet and an airways clearance had not been requested by the tug/glider combination. Both pilots of the tug/glider combination advised that they had not seen VH-DLF and were unaware that they had violated controlled airspace.
