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A DeHavilland Dash 8 was conducting an instrument flight rules (IFR) Air Transport flight from Sydney to Narrabri and tracked via Richmond direct to Narrabri at flight level (FL) 180. The flight was conducted in controlled airspace until approximately 130 NM north-north-west of Sydney. The remainder of the flight was then conducted in Class G non-controlled airspace. The crew of the Dash 8 contacted Sydney Flight Service (FS3) at 0721 Eastern Summer Time (ESuT) and reported that the aircraft was maintaining FL180 with an estimate for Narrabri of 0745. (All times are ESuT unless otherwise stated.)

At 0732 the pilot of a Piper Chieftain conducting a visual flight rules (VFR) flight from Wee Waa to Tamworth made an all-stations broadcast on the FS3 frequency. The pilot reported departing from Wee Waa at 0730, tracking 113 (degrees M) and climbing to 7,500 ft. The pilot addressed the report to FS3 and to any other traffic in the Wee Waa area. There was no acknowledgement or response to this report by other aircraft or ground stations. The pilot was rated and licensed for IFR flight but elected to operate VFR for this flight and therefore FS3 was not required to take any action in response to his broadcast.

Approximately 4 minutes after the Chieftain pilot's departure report, the crew of the Dash 8 requested traffic information from FS3 for their descent into Narrabri. FS3 advised that there was no known IFR traffic. The crew acknowledged this advice and reported that the Dash 8 had left FL180, but they did not include their position relative to Narrabri in the transmission.

The track of the Chieftain crossed the track of the Dash 8 approximately 12 NM south-southeast of Narrabri.

As the Dash 8 was passing 8,000 ft, the crew saw a reflection to the left of the nose of their aircraft. Subsequently, they saw a twin-engine aircraft and manoeuvred their aircraft to avoid it. The twin-engine aircraft passed from left to right approximately 300 m in front of them and at about the same level.

The crew of the Dash 8 queried FS3 regarding the other aircraft but were advised that there was no IFR traffic. The crew of the Dash 8 then made an all-stations area broadcast in an attempt to establish communications with the other pilot. The pilot of the Chieftain acknowledged the call and advised the crew that he was tracking from Wee Waa to Tamworth at 7,500 ft and that his aircraft was a Chieftain.

Further discussion established that the pilot had neither seen the Dash 8 nor heard the crew reporting on descent. The crew of the Dash 8 did not remember hearing the departure report from the pilot of the Chieftain.

Traffic information

In non-controlled airspace, flight service are required to provide information to all IFR-category aircraft on other IFR flights to assist crews in determining any conflict situations. However, the flight service information system does not cover VFR traffic. Therefore, in this instance FS3 was not required to provide information on VFR flights to the crew of the Dash 8.

Aircrew are responsible for maintaining their own separation in non-controlled airspace. IFR pilots use known position reports of other aircraft to gain an appreciation of the disposition of traffic and whether there is a need to arrange separation. Pilots of VFR flights are only required to make a limited number of position reports and generally rely on the unalerted "see and avoid" principle to maintain separation from other aircraft; that is, they maintain a continuous lookout for other aircraft.

Radio frequency monitoring

The Chieftain was fitted with two very high frequency (VHF) radios. The pilot selected one to the common traffic advisory frequency (CTAF) and one to the FS3 area frequency while in the Wee Waa CTAF area. After leaving that CTAF area, he changed from the CTAF to the Tamworth automatic terminal information service (ATIS) frequency on one radio while continuing to monitor FS3 on the second radio.

The investigation estimated from aircraft performance data that the Chieftain would have reached the planned level of 7,500 ft just prior to the Dash 8 crew requesting traffic information from flight service. The Chieftain pilot reported that at about that time he was probably listening to the Tamworth ATIS in preparation for requesting a clearance to enter controlled airspace from air traffic control.

The Dash 8 was also fitted with two VHF radios. While operating in controlled airspace, the crew selected the air traffic control frequency on one radio while the other was selected to the aviation emergency frequency. Prior to leaving controlled airspace, the crew selected the FS3 area frequency while continuing to monitor the emergency frequency on the second radio.


The Wee Waa departure report from the pilot of the Chieftain was recorded on the flight service automatic voice recording (AVR) system and was clear and understandable. This departure report was additional to the mandatory reports for VFR flights detailed in the Aeronautical Information Publication (AIP) RAC 64.

AIP RAC 42 paragraph 32.2 required the crew of an IFR aircraft to report their aircraft's position to flight service prior to changing levels. Company operating procedures for the Dash 8 required the crew to make a position report prior to descent when operating in non-controlled airspace. The AVR did not record a position report from the crew of the Dash 8 prior to their commencement of the descent.

Environmental aspects

The visibility was reported as hazy but in excess of 10 km. The sun was low in the sky and the pilot of the Chieftain had lowered the sun-visor in the aircraft cabin to shield his eyes.

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