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VH-ITQ was approaching Mudgee at 6000 feet tracking 203 degrees from Tamworth. Flight Service (FS) advised that VH-UJX was conducting airwork at Mudgee up to 6000 feet and would be departing for Tamworth in about six minutes. The pilot of ITQ was unable to contact UJX on either FS or the common traffic advisory frequency (CTAF). UJX was subsequently sighted in close proximity, proceeding in the opposite direction to ITQ and entering cloud. At that time UJX was about 100 feet higher than ITQ. Monitoring of the FS tape showed that at the time ITQ changed to CTAF to contact UJX, UJX had left CTAF to call FS. UJX gave a departure call to FS indicating the aircraft was maintaining 6000 feet. FS then gave UJX traffic on ITQ and UJX then corrected part of the departure call saying they were on climb to 7000 feet which was the flight planned altitude for UJX. In a discussion about the incident, the pilot in command of UJX said that the aircraft was equipped with only one VHF radio set which meant that it was not possible to monitor both FS and CTAF at the same time. Had this been possible then this incident could have been avoided. The aircraft was about to have a second VHF set fitted. He also said that they had departed the CTAF before requesting traffic which was an error on their part and which would not normally be done. It is worth noting that the same incident could still have occurred even if UJX had not departed the CTAF without first getting traffic from FS. This is because UJX was airworking in the CTAF up to 6000 feet (the cruising altitude of ITQ) and could just have easily been in almost the same position at the same time and missed making contact with the overflying aircraft due to simultaneous frequency changes. This would be particularly true if ITQ did not change to CTAF until close to the CTAF boundary. Significant Factors The following factors were considered relevant to the development of the occurrence: 1. The two aircraft missed communicating with each other because they were not on the same frequency at the time ITQ called UJX. 2. UJX was fitted with only one VHF radio set and therefore could not monitor both the CTAF and FS frequencies at the same time. 3. The present design of the airspace system contributes to this type of occurrence. 4. UJX departed the CTAF before getting traffic information.
General details
Date: 16 August 1993 Investigation status: Completed 
Time: 11:32 EST Investigation type: Occurrence Investigation 
 Occurrence type:Near collision 
 Occurrence class: Airspace 
Release date: 19 June 1994 Occurrence category: Incident 
Report status: Final  
Aircraft 1 details
Aircraft manufacturer: Piper Aircraft Corp 
Aircraft model: PA-28-161 
Aircraft registration: VH-ITQ 
Sector: Piston 
Damage to aircraft: Nil 
Departure point:Tamworth NSW
Destination:Mudgee NSW
Aircraft 2 details
Aircraft manufacturer: Piper Aircraft Corp 
Aircraft model: PA-30 
Aircraft registration: VH-UJX 
Sector: Piston 
Damage to aircraft: Nil 
Departure point:Mudgee NSW
Destination:Tamworth NSW
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Last update 24 July 2015