On 12 June 2015, Nauru Airlines, Boeing B737-300, reg VH-NLK, were on a non- directional beacon/distance measuring equipment (NDB/DME) approach into Kosrae airport in Federated States of Micronesia. During the approach, at night and in instrument meteorological conditions, the aircraft descended below the minimum descent altitude and three enhanced ground proximity warning system (EGPWS) ‘too low terrain’ alerts were triggered.
A go-around was performed prior to the aircraft reaching the missed approach point. During the go-around, the airspeed decayed and required the pilot to use full thrust. The flight crew identified and corrected the barometric pressure setting and the subsequent approach and landing into Kosrae were uneventful.
What the ATSB found
The flight crew did not complete the approach checklist before commencing the non-precision NDB approach into Kosrae, resulting in the barometric pressure setting on the altimeters not being set to the local barometric pressure. This resulted in the aircraft’s altitude being lower than what the pressure altimeter was indicating to the pilots. The aircraft descended below the EGPWS terrain clearance floor profile for the Kosrae runway, resulting in three separate EGPWS alerts.
The flight crew initiated a missed approach when they lost visual contact with the runway. The captain was experiencing fatigue and the flight crew had an increased workload and stress due to the inaugural RPT flight into Kosrae at night in rapidly deteriorating weather. As a result, the crew’s decision making and task execution on the missed approach were affected, and the aircraft state, airspeed and attitude were not effectively monitored by either crew member.
Pilots fatigue and stress-inducing circumstances that may have an impact on their flying performance, therefore operators also need to remind flight crew of the importance of their decisions with regards to their fitness to fly.
For flight crews, the importance of completing approach checklists and monitoring the approach at safety critical times is emphasised.
For operators, the occurrence highlights the importance of incorporating dual-engine go-arounds into simulator training sessions.