Airbus Industrie A320-211, VH-HYY, Melbourne, Aero. Vic. 25 October 1999

1. The Adelaide flight progress strip in the tower was misplaced on the airways clearance delivery console during the handover/takeover of the surface movement control/airways clearance delivery positions.
2. The coordinator did not review the flight progress strip to ensure the crew had been cleared before coordinating the Sydney flight data record for VH-HYY.
3. The absence of ticks on the Sydney flight progress strip did not alert controllers to the fact that a clearance may not have been read back or issued.

Although the annotated Adelaide flight progress strip was accidentally placed on the airways clearance delivery console during handover/takeover, there were at least two chances of detecting the error (at the coordinator and aerodrome control positions, for instance) before the aircraft departed. The controllers were supposed to ensure that the flight progress strip annotations reflected the current status of the flight. They should have ticked the clearance to show that it had been issued and read back. Perhaps the controllers assumed the strips were correct because they had been forwarded from at least one other position. Alternatively, the controllers at the positions may have been distracted while managing other aircraft or tasks.

Because air traffic controllers need accurate flight information, they have to continuously assess and confirm data from different sources. Even if crews provide the destination when asking for taxi clearance, mistakes can still happen if controllers do not scrutinise the information.

The Australian Advanced Air Traffic Control System (TAAATS) held
two flight data records for VH-HYY, one from Melbourne to Adelaide
and the other from Melbourne to Sydney. The crew were cleared to
Adelaide but the Sydney flight data record was coordinated in
TAAATS. After the aircraft departed, the controller saw that its
radar track did not "couple" with the flight data record. This was
achieved when the air traffic system linked an aircraft's secondary
surveillance radar track with the flight data record assigned to
that code. Separation standards were not infringed.

Airservices Australia found that, in anticipation of a busy
departure period, the controller operating the combined surface
movement control and airways clearance delivery positions noted
clearance details on all pending flight progress strips. The
controller cleared the crew of HYY for Adelaide and ticked the
clearance and altitude annotations on the strip after receiving a
correct read-back. This was required to confirm that the clearance
had been issued and read back correctly. After the surface movement
control and airways clearance delivery positions were individually
activated, and during handover/takeover, the Adelaide strip for HYY
was accidentally placed on the airways clearance delivery console
and the Sydney strip placed on the surface movement control
console. When the crew sought a taxi clearance, the surface
movement controller did not notice that the clearance annotated on
the Sydney strip was unticked but still activated the strip. The
strip was then passed to the coordinator position and the
controller there changed the state of the HYY flight data record in
preparation for the aircraft's departure. The coordinator processed
the first observed record for that aircraft and did not notice that
the clearance had not been ticked. The departure controller then
received a system "preactive" electronic strip showing that HYY was
taxiing for a departure to Sydney. The strip in the tower was then
passed to the aerodrome control position. Neither of the two
controllers staffing that position noticed that the clearance on
the HYY strip had not been ticked. Controllers at each operating
position were required to maintain and arrange their strips.

Because TAAATS gave a separate secondary surveillance radar code
to each flight data record in the system, the Adelaide and Sydney
flight data records for HYY had different codes. The HYY crew were
later cleared for takeoff and after departure, the Sydney flight
data record did not link to the aircraft's radar track. After
confirming that the aircraft track displayed on the radar was that
of HYY, the departure controller told the crew to select the
aircraft's transponder on the secondary surveillance radar code
assigned to the Sydney flight data record. The track then linked to
the flight data record and the electronic strip on the departure
controller's display changed to active. Shortly after, the
departure controller gave an amended clearance to the crew of HYY
for direct tracking to Sydney. The crew replied that the flight was
to Adelaide.

The Aeronautical Information Publication AIP GEN 3.4-36-38 gives
the radiotelephony phraseology required around an aerodrome. When
pilots seek a clearance and clearance delivery is in operation,
they must provide the aircraft's flight number and the aerodrome
where they first plan to land. When they seek a clearance to taxi,
they may include this aerodrome if they wish. The automatic voice
recording confirmed that the HYY crew had supplied their
destination when seeking a clearance but that they did not include
it when asking for a taxi clearance. In other words, they had
complied with the AIP radiotelephony phraseology procedures.