On 27 May 2003, at about 1650 Western Standard Time, the pilot
of a Cessna 172P (C172) aircraft, registered VH-AUC, was conducting
circuits on runway 06 right (06R) at Jandakot. An instructor and
student pilot of a Piper PA-38-112 (Tomahawk) aircraft, registered
VH-FIG, were also conducting circuits on runway 06R.
While on downwind for runway 06R, the pilot of the C172
requested a landing on runway 06 left (06L). The aerodrome
controller responsible for runway 06R (ADC1) acknowledged that
request and instructed the pilot of the C172 to follow the
Tomahawk, which was also on downwind for runway 06R. After
coordinating with the aerodrome controller responsible for runway
06L (ADC2), the ADC1 cleared the pilot of the C172 to make an
approach to runway 06L and instructed the pilot to transfer to the
ADC2 frequency. The C172 subsequently passed in close proximity to
the Tomahawk while the Tomahawk was on final for runway 06R and the
C172 was on right base leg for runway 06L.
Radar data indicated that the crew of the Tomahawk had extended
downwind for sequencing with a preceding aircraft and did not turn
base for runway 06R until close to the control zone boundary. Radar
data also indicated that the pilot of the C172 had turned right
base for runway 06L from a late downwind position and had flown an
oblique base leg to join final for runway 06L. Sun glare may have
contributed to the C172 pilot losing sight of the Tomahawk ahead
after it had turned onto the base leg.
The Tomahawk was at about 500 ft above ground level and
descending on long final approach to runway 06R when the instructor
observed the C172 tracking towards them. The instructor in the
Tomahawk attempted to contact the pilot of the C172, but used the
callsign of another aircraft believed to be operating in the
circuit at the time and received no response. Regardless, the pilot
of the C172 would not have heard any transmissions from the
instructor, as the pilot was operating on a different frequency, as
instructed by ADC1.
The Tomahawk instructor increased the rate of descent of the
aircraft and monitored the position of the C172 before it passed
directly overhead, left to right, about 50 ft above their aircraft.
The instructor reported that the C172 was sighted approximately 20
seconds before it passed overhead. The C172 pilot was unaware of
the incident until after landing when it was brought to his
attention by the surface movement controller. Due to the distance
from the control tower and the angle of observation, the aerodrome
controllers could not accurately judge the relative positions
between the aircraft on base and final approach.
Following this incident, Airservices Australia issued
instructions to Jandakot aerodrome controllers to delay, where
practicable, the transfer of aircraft onto another frequency when
facilitating a change in landing runway.