On 10 January 2013, the crew of an Embraer Regional Jet 170 (E170), registered VH-ANO and operated by Airnorth, were flying from Darwin to McArthur River Mine, Northern Territory. Shortly after passing navigational waypoint SNOOD, 125 NM (232 km) north-west of McArthur River Mine, the aircraft’s flight path started diverging from its planned track. The problem was identified by air traffic control and the crew were advised. The aircraft was re-cleared direct to the initial approach fix and continued to McArthur River Mine.
What the ATSB found
The ATSB found that, while updating the aircraft’s flight management system for the descent into McArthur River Mine, the crew unintentionally omitted entering an intended navigational waypoint that was located 25 NM (46 km) north-west of McArthur River Mine. This omission resulted in the aircraft’s autopilot tracking the aircraft direct to the initial approach fix instead of first tracking to the intended waypoint. The crew’s crosschecking processes were not effective in identifying the data input error.
Although it could not be concluded as contributing to the crew’s errors, the ATSB also found that, due to restricted sleep in the previous 24 hours, the crew were probably experiencing a level of fatigue known to have a demonstrated effect on performance. Although the operator’s rostering practices were consistent with the existing regulatory requirements, it had limited processes in place to proactively manage its flight crew rosters and ensure that fatigue risk due to restricted sleep was effectively minimised.
What's been done as a result
Airnorth advised that since the occurrence, the number of E170 flight crew has been augmented, increasing its rostering flexibility. Furthermore, due to schedule changes, the operator no longer used any roster pattern that resulted in planned rosters with flight crews receiving less than 10 hours time off duty overnight.
Although not in response to this occurrence, the Civil Aviation Safety Authority has released revised fatigue management and flight and duty time requirements in Civil Aviation Order (CAO) 48.1 Instrument 2013. These new requirements either require operators to have a fatigue risk management system, or operate to more restrictive requirements regarding minimum time off duty than those which previously applied.
This occurrence reinforces the importance of all pilots and operators conducting systematic and comprehensive checks of all data entered into flight management systems, and the importance of continually monitoring the effects of data input on an aircraft’s flight path.