A Cessna 310, VH-DWS, was maintaining 7,000 ft outbound from Kalgoorlie to Forrest via the standard instrument flight rules (IFR) route. VH-LAE, a Cessna 402, was maintaining 10,000 ft from Forrest to Kalgoorlie, also on the standard IFR route. Both aircraft were between reporting points Sevsi and Seemo, in cloud, and were using high frequency (HF) radio to communicate with Perth Flight Service (FS). At approximately 1236 WST, the pilot of LAE requested traffic for descent to 6,000 ft because the aircraft had encountered icing conditions, but the HF communication conditions were poor and FS did not understand the request. The next 6 minutes were spent by FS trying to establish communications with LAE. In the meantime, LAE had commenced descent to clear the conditions, unaware of the existence of DWS. The pilot of LAE reported that he had made a general broadcast on HF and very high frequency (VHF) radios before commencing descent, although the broadcasts were not recorded by FS or heard by the pilot of DWS. At approximately 1243, DWS was given traffic information on LAE. The pilots of the two aircraft then contacted each other on the area VHF frequency and established that LAE and DWS had crossed and were now 11 NM apart at 6,000 ft. LAE had passed through DWS's level on a reciprocal track. The separation between the aircraft as they crossed could not be established.
In reviewing the Aeronautical Information Publication (AIP) communication procedures, it was noted that although dual (HF and VHF) area broadcast requirements are specified in the AIP Air Traffic Rules and Services (RAC) section, the Operations (OPS) section does not detail the same requirement. OPS 58 specifies the radio telephony requirements outside controlled airspace without including the dual broadcast procedures.
SAFETY ACTION
As a result of this investigation, the Bureau issued Safety Advisory Notice SAN980018 to the Civil Aviation Safety Authority (CASA) on 26 February 1998. This Safety Advisory Notice alerted CASA to the inconsistencies in the AIP regarding the requirements for radiotelephony reports on both HF and VHF radios in non-controlled airspace.
A response was received from the Civil Aviation Safety Authority on 12 May 1998, which stated:
"CASA has reviewed the information provided in the Safety Advisory Notice and will amend the AIP as BASI has proposed".
BASI response status: Closed - Accepted