Loss of separation involving a Boeing 737-476, VH-TJE, Perth Aerodrome, Western Australia, on 10 June 1998

The aerodrome controller (ADC) at Perth tower had cleared the Boeing 737 to line up on runway 21. An Airservices Australia car was accompanying the airfield mower cutting grass at the runway's edge, approximately midway along the runway. The ADC was aware that the car was just within the flight strip but he was not aware of the existence of the mower. Only after he cleared the 737 to take off and it had begun rolling, did he become aware of the mower and its close proximity to the runway. He instructed the pilot of the 737 to cancel the take-off.

The surface movement controller (SMC), who had not heard the take-off clearance, became aware of impending confliction when the aircraft began rolling. He instructed the car to vacate the flight strip. The aircraft stopped approximately 600 m before the original position of the mower having rolled approximately 750 m. The mower was a small blue vehicle and was approximately 1500 m from the tower and would have been difficult to see from the tower. The ADC had taken over the position approximately 10 minutes prior to the incident. He reported that he could not recall being advised about the mower during the handover so the ADC was unaware of the mower's existence.

However, the "runway occupied" strip had been placed in the ADC's departure runway designator console but because the ADC did not post the aircraft's flight strip on the console before clearing the aircraft for take-off, he did not note that the mower's operation near runway. The manual of air traffic services (MATS) details a requirement that an aircraft not be issued with a take-off clearance until its flight strip has been placed under the "runway occupied" strip at the ADC console and the runway has been vacated. When the ADC issued the take-off clearance, he had assumed that the SMC had ensured that the runway was vacated although he had not coordinated with the SMC to ensure that such was the case.

The tower coordinator normally supervised the operations within the tower but he was pre-occupied at the time recording information for the automatic terminal information service (ATIS). He had, therefore, not noticed the incident developing until the aircraft had begun its take-off run. He reported that he then called to the ADC to stop the aircraft because there was a vehicle on the runway.

LOCAL SAFETY ACTION

Airservices Australia has issued a local instruction highlighting the necessity of full handover procedures and a requirement to address escort vehicles with their callsign and escorted company on all radio communications and during tower coordination.