A near collision at Mildura has prompted the ATSB to highlight the value of non-mandatory radio calls at CTAFs.
In June last year, Warrior VH-ENL and Qantaslink Dash 8 VH-TQH departed simultaneously from separate crossing runways, missing each other by about 600 metres.
According to the ATSB, the Warrior pilot lined up on runway 36 could not see the departing Dash 8 on runway 27 because the view between the two thresholds was obscured.
The ATSB investigation report released this week says the Warrior pilot initially mis-identified his runway as "runway 35", prompting the Dash-8 crew to believe the Warrior could have been at Wentworth Airport, which shares the CTAF.
“This occurred while the Dash 8’s pilots were obtaining their pre-departure information from air traffic control, and had the volume turned down on the CTAF radio,” ATSB director Dr Stuart Godley explained.
“In addition, the Dash 8 crew only received certain elements of the Cherokee’s calls due to an over transmission from air traffic control.”
Both aircraft made back-tracking calls on their respective runways, but the Cherokee pilot did not finish the transmission with the required "traffic Mildura."
When the Cherokee began its take-off roll on runway 36, the pilot believed the Dash 8 would still be backtracking 09, when it was really about to start its own take-off roll.
“Subsequently, both aircraft began take-off rolls towards the intersection of their respective runways, and the Dash 8 passed about 600 m in front of the Cherokee,” Godley said
Investigators determined that the Cherokee pilot gave a rolling call on the CTAF using the correct runway number, while the Dash 8 crew did not – but that rolling calls are not mandatory.
“With the inability to see another aircraft when each aircraft is at the threshold at Mildura Airport, the lack of a requirement for mandatory rolling calls increased the risk of aircraft not being aware of each other immediately prior to take-off," Godley said.
"Pilots can guard against occurrences like this one by making the recommended broadcasts when in the vicinity of a non-controlled aerodrome, actively monitoring the CTAF while maintaining a visual lookout for other aircraft and constructively organising separation through direct contact with other aircraft."
Since the incident, Mildura Airport has published a NOTAM for mandatory rolling calls from all aircraft immediately prior to take-off.
The full report is on the ATSB website.