Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation.
What happened
On 15 May 2018, at about 1500 Western Standard Time (WST), a Fokker F100 was on a scheduled passenger flight from Perth, Western Australia (WA) to Kununurra, WA. The flight crew was comprised of the captain and the first officer (FO).
Passing through 10,000 ft on descent, the crew received a “LG Not Down”, triple chime alert. The flight crew identified that that the Radio Altimeter 1 (RA1) was erroneously indicating ‘zero feet’, which triggered the gear unsafe alert. The flight crew discussed the situation and decided to configure the aircraft for landing early, with the view to extend the gear as soon as practicable, in order to silence the triple chime alert.
Shortly after, the crew observed the autopilot disconnect and a ‘STAB TRIM 1 and 2’ fault alert. The captain took over flying the aircraft manually, commenced speed reductions and called for ‘Flaps 8’. Immediately following, RA1 appeared to return to normal operation and all alerts ceased.
Descending through 7,000 ft, RA1 returned to a reading of ‘zero feet’. The flight crew observed all of the previous alerts, in addition to a “TOO LOW GEAR” GPWS alert. The crew reviewed the situation and agreed to continue with the plan to configure the aircraft early for landing. The remainder of the approach and landing were conducted without further incident.
Once on the ground, the captain contacted Maintenance Watch and the Manager Flight Technical for guidance. In preparation for the return flight to Perth that afternoon, the team made the decision to dispatch the aircraft under the Minimum Equipment List (MEL).
At about 1630 WST, after a lengthy turnaround, the flight crew began the performance calculations for take-off on runway 12. The take-off flap position of ‘Flaps 15’ was correctly identified and circled on the Take-Off and Landing Data (TOLD) Card, to highlight the infrequently used setting.
After start, the flight crew became aware of an inbound aircraft on long final. The flight crew initiated a radio call to the crew on board the approaching aircraft to confirm their intended surface movements. As the departing aircraft approached the runway, the other aircraft made a radio transmission expressing confusion regarding the use of the taxiways. The confusion was resolved and the captain of the departing aircraft began the pre-take off sequences.
Distracted by the earlier confusion and eager to depart, the captain called for ‘Flaps 8’, the more commonly used take-off configuration. The captain then glanced at the TOLD card to cross check the numbers and continued with the take-off.
The aircraft’s speed had climbed above 100 kts before the FO and captain identified the incorrect flap setting. The captain called continue and the take-off was completed without further incident.
Safety message
This incident highlights the importance of managing operational pressures and distraction. The traffic on the taxiway, the events of the previous flight and the extended turnaround time had distracted the crew from completing the pre-flight sequences in a conscious manner. During times of high workload, distraction and perceived time pressures can often lead to human error.
External pressures and distractions are sometimes unavoidable, however, there are effective ways to manage them, as discussed in the ATSB research report B2004/0324, ‘Dangerous distraction: An examination of accidents and incidents involving pilot distraction in Australia between 1997 and 2004’.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.