The crew of a Metro 23 was cleared by the surface movement controller (SMC) at Perth to enter runway 11 and taxi to the threshold of runway 21 prior to departure. However, as the aircraft approached the runway 11 holding point, the crew checked the final approach path and saw a Cessna C402 landing on runway 11 in front of them.
A subsequent investigation revealed that the SMC had previously been using runway 11/29 as a taxiway for vehicle and aircraft movements. The procedure for release of the runway from the aerodrome controller (ADC) to the SMC was for both the ADC and SMC to de-select their respective runway 11/29 selection buttons. Both buttons would became illuminated when selected on, indicating that the runway was active. De-selecting each button had the reverse effect. Should the button be selected or de-selected on one side only, both lights would flash to alert the controllers to a mismatch.
In addition to the use of the runway selection buttons, both controllers were to coordinate off-line with each other using the phrase "runway 11/29 released to you" or "runway 11 active" as appropriate. Any traffic that might be on the runway would also be coordinated. Those procedures were detailed in the Perth Tower Local Instructions.
Just prior to the incident, the SMC had control authority for runway 11/29, and the runway 11/29 selector buttons were in the de-selected position. When the crew of the Metro requested a taxi clearance, the SMC cleared them to taxi to runway 21, entering runway 11 at taxiway Echo. The threshold of runway 21 is at the midway point of runway 11/29 and access to the threshold of runway 21 was achieved by taxiing via runway 11. Once details of the Metro were no longer required by the SMC, the flight progress strip for the aircraft was placed into the top transfer slot on the ADC's side of the console. This procedure was also documented in Perth Tower Local Instructions.
Three minutes after the taxi clearance was issued, the ADC elected to land a C402 on runway 11. Prior to issuing the landing clearance, the ADC selected the runway 11/29 selector button to indicate to the SMC that the ADC was taking control authority for runway 11/29. Because the SMC no longer held a flight progress strip as a memory marker, he also turned on his selector button and advised the ADC "no traffic runway 11". The ADC did not notice the Metro, which had not yet entered taxiway Echo, nor did he notice the flight progress strip in the top transfer slot. The ADC subsequently cleared the C402 to land on runway 11.
The SMC did not conduct an effective scan of the airfield prior to advising the ADC of "no traffic".
The ADC did not conduct an effective scan of runway 11 or the flight progress strip display prior to clearing the C402 to land.
The flight progress strip display, and the controller's management of the console, did not provide the controllers with an accurate representation of the traffic situation.
The airfield layout increased the potential for a runway incident.
ATC Management at Perth has made the following recommendations:
- the use of runway 11/29 be restricted to only when operationally required;
- local Instructions be amended to ensure the SMC retains the flight progress strip on an aircraft until the aircraft is no longer under the SMC's control; and
- local ATC management to continue with its aim of having runway 11/29 withdrawn from operational use due to the traffic management complexities created by its use.
BASI Safety Action
As a result of this and other occurrences, the Bureau of Air Safety Investigation is investigating a safety deficiency.
The deficiency relates to the use of conditional 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.
|Date:||14 September 1998||Investigation status:||Completed|
|Time:||1520 hours WST|
|State:||Western Australia||Occurrence type:||Loss of separation|
|Release date:||10 July 2000||Occurrence class:||Airspace|
|Report status:||Final||Occurrence category:||Incident|
|Highest injury level:||None|
Aircraft 1 details
|Aircraft manufacturer||Fairchild Industries Inc|
|Type of operation||Charter|
|Damage to aircraft||Nil|
|Departure point||Perth, WA|
|Destination||Sunrise Dam, WA|
Aircraft 2 details
|Aircraft manufacturer||Cessna Aircraft Company|
|Type of operation||Unknown|
|Damage to aircraft||Nil|
|Departure point||Jandakot WA|