Australian investigators have warned about the effects of expectation and inattention after three turboprops departed a regional airport without activating runway lights.
Gladstone airport is uncontrolled, with no tower. Pilots use a common traffic radio frequency to transmit signals to a response unit which switches on the lights of its single runway, designated 10/28.
Once active the lights stay on for 30min, with automated audio and visual warnings when the remaining duration falls below 10min.
But the inquiry found that the lights switched off as a Skywest Airlines ATR 72 conducted its take-off roll for a service to Brisbane on 16 May this year.
The following day, at almost the same time in the evening, the crew of another Skywest ATR 72 failed to activate the lights before take-off.
It was followed by a QantasLink Bombardier Q400 which departed without lighting for taxiing or take-off.
"There was no indication that the system was malfunctioning on the nights of the occurrences," says the Australian Transport Safety Bureau.
It points out that the airport is surrounded by well-lit commercial buildings, which provide a high level of ambient lighting.
But the ATSB adds that runway lights are designed to indicate runway ends and improve navigation and guidance for pilots.
While not issuing safety recommendations, the ATSB says the incidents highlight the risks associated with change blindness - a failure to notice a difference in visual environment - and inattention blindness, when pre-occupation results in failure to notice an unexpected visual cue. It also indicates that expectation bias played a role.
All the pilots stated that they were not aware of the loss of runway lighting between boarding and departure, nor did they recall the 10min warning, although they added that the aircraft lights provided substantial illumination.
Skywest has said it is reminding crews to cycle the runway lights before engine start while QantasLink is establishing policies regarding lighting verification, and looking to encourage continuous lighting at airports during peak periods.