024/10

The controllers were unaware of the activation of the STCA, which remained illuminated for about 30 seconds before the 2 aircraft crossed. The STCA is potentially a controller’s last defence for averting a collision and needs to be acknowledged in every case. The lack of response in this incident may indicate that either the STCA activation indications were not effective or controllers had become desensitised to the indications due to a high number of 'nuisance' alerts, or a combination of both.
The Commission believes this is a safety issue that the Director needs to address with Airways and recommends that Airways be required to review the operation of the STCA to ensure it is effective in reducing the risk of a collision and that controllers are sufficiently aware of the risk of ignoring what might be perceived as nuisance alerts.