The pilot of the Beechcraft Bonanza was conducting a Global
Positioning System (GPS) instrument approach into Lilydale from
waypoint "charlie" which was located 15 NM north of Lilydale. As
the pilot approached waypoint "India", a position 5 NM south of
"charlie", the controller advised the pilot that he was two and a
half miles east of "charlie". When the pilot advised that he was
just passing waypoint "india", the controller responded that he was
not and that he was, in fact, two and a half miles east of
"charlie".
The pilot decided not to follow the controllers information and
conducted a missed approach. Just as the pilot commenced the missed
approach procedure, he became visual and was able to visually
establish that his position was accurate and, as he expected, on
the GPS approach track. The pilot continued the approach
visually.
The pilot later reported that he had checked all of the
available information and had verified that he was tracking via the
correct GPS track. When the controller advised him that he was 2.5
NM east of "charlie" the GPS indications were within 0.13 NM of
waypoint "india". The pilot reported that he checked the GPS
function with an accompanying pilot and found no error.
The investigation revealed that the controller had never seen
this approach being flown in instrument meteorological conditions
before. In an attempt to educate himself about the Lilydale GPS
approach, the controller used the bearing and range line to
graphically display the last two positions of the approach on the
air situation display. The controller misread the approach plate
and displayed incorrect waypoints on the air situation display. The
controller used this incorrect display to provide positional
information to the pilot.
Following this occurrence, Airservices Australia developed an
electronic selectable map, based on verified data, available on the
air situation display to display all of the waypoints associated
with the Lilydale, Moorabbin and Avalon GPS approaches.