Breakdown of co-ordination between a Boeing Co 737-476, VH-TJG and a Pilatus PC-12, VH-FMC, Adelaide Airport, South Australia, on 26 September 1998

The crew of a Boeing 737 (B737) was cleared by the Adelaide surface movement controller (SMC) to taxi to the Foxtrot 5 holding point for runway 05, and to cross runway 30. Earlier, the SMC had been issued with a blanket clearance by the aerodrome controller (ADC) that allowed aircraft to occupy or cross runway 30 without a specific clearance from the ADC. The use of a blanket clearance reduced the need for segmented taxi clearances.

There were three personnel rostered for duty in the control tower; an ADC, a SMC and a tower coordinator. At the time of this occurrence the tower coordinator was absent from the tower cabin, reducing the monitoring potential of tower staff. All staff were appropriately trained and rated.

While the SMC was issuing the taxi clearance to the crew of the B737, the ADC was arranging departure instructions for a Pilatus PC12 from runway 30. The ADC subsequently cleared the Pilatus to take off from runway 30, without first cancelling the blanket taxi clearance and resuming control of the runway. Shortly after issuing the take-off clearance, the ADC became involved in communications with the approach controller regarding other inbound aircraft. The SMC was occupied with other data processing duties.

The crew of the B737 had sighted the Pilatus in the lined-up position on runway 30, but was unaware that a take-off clearance had been issued to that aircraft. As the B737 approached the crossing point of runway 30 on taxiway Foxtrot 2, the crew saw the Pilatus commence to take-off. They applied heavy braking and stopped their aircraft with the nosewheel 1-2 m beyond the runway holding point. The Pilatus continued its take-off run. The crew of the B737 subsequently confirmed with the SMC that they had been cleared to cross runway 30.

The local procedures in the Adelaide tower for a blanket clearance of a runway release required the use of a bright yellow coloured flight progress strip with the words "RUNWAY 12/30 OCCUPIED". Although a strip was correctly placed in each of the strip presentation bays in front of both the SMC and the ADC to indicate that a blanket clearance was issued, that procedure failed to attract the attention of the ADC.

The investigation of this occurrence was carried out by Airservices Australia, monitored by a Bureau investigator. A number of significant factors were identified.

The ADC did not conduct an effective scan of runway 30 or the flight progress strip display prior to clearing the Pilatus to take off.
The presentation of the yellow flight progress strip did not alert the ADC that a runway 12/30 blanket clearance was in place.
The ADC did not hear the SMC issue a clearance for the crew of the B737 to cross runway 30, nor did the SMC hear the ADC issue a take-off clearance to the Pilatus.
The ADC did not observe the B737 moving towards runway 30.
The SMC was distracted from a surveillance role by other tasks.
The absence of the Tower Coordinator reduced the potential for recognising the development of a safety occurrence.

Local Action

ATC management has tasked the Adelaide tower team leaders to review procedures to prevent a future recurrence.

BASI Safety Action

As a result of this and other occurrences, the Bureau of Air Safety Investigation is investigating a perceived safety deficiency relating to the use of blanket clearances for runway entry and runway crossings by vehicles and aircraft, and the procedures used by air traffic controllers to alert themselves that vehicles or aircraft are on an active runway.

Any recommendation issued as a result of this deficiency analysis will be published in the Bureau's Quarterly Safety Deficiency Report.