ASN Aircraft accident Boeing 737-33A VH-NLK Kosrae Airport (KSA)
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Status:Accident investigation report completed and information captured
Date:Friday 12 June 2015
Type:Silhouette image of generic B733 model; specific model in this crash may look slightly different
Boeing 737-33A
Operator:Nauru Airlines
Registration: VH-NLK
MSN: 23635/1436
First flight: 1987-08-20 (27 years 10 months)
Engines: 2 CFMI CFM56-3B1
Crew:Fatalities: 0 / Occupants: 7
Passengers:Fatalities: 0 / Occupants: 69
Total:Fatalities: 0 / Occupants: 76
Aircraft damage: None
Location:5,3 km (3.3 mls) SW of Kosrae Airport (KSA) (   Micronesia)
Phase: Approach (APR)
Nature:International Scheduled Passenger
Departure airport:Majuro-Amata Kabua International Airport (MAJ/PKMJ), Marshall Islands
Destination airport:Kosrae Airport (KSA/PTSA), Micronesia
The Nauru Airlines Boeing 737-300 aircraft, registered VH-NLK, operated a scheduled passenger flight originating in the Republic of Nauru and transiting Tarawa, Republic of Kiribati, and Marshall Islands Airport, Majuro atoll, Republic of the Marshall Islands, to Kosrae Airport and finally Pohnpei Airport, both in the Federated States of Micronesia (FSM). This was the operator's inaugural scheduled regular public transport service to Kosrae and Pohnpei.
Travelling on-board were the Nauruan President, the Nauruan Minister of Aviation, and the Chairman of the Board of Directors of Nauru Air Corporation. In the six weeks preceding this flight, the operator had flown three charter flights to the FSM airports. The captain also stated that he had flown a couple of charter flights (during the day) into Kosrae before this inaugural scheduled service.
The flight was originally scheduled to leave Nauru at 02:30 UTC (14:30 Nauru Time). However, a technical issue with the original aircraft led to a change to VH-NLK. This resulted in the aircraft departing 60 minutes late.
The sector from the Marshall Islands to Kosrae was delayed a further 17 minutes due to ground handling issues. The flight departed after last light at 07:40 and the planned flight time was 1 hour 19 minutes. The approach and landing at Kosrae was at night.
For this sector, the captain was the pilot flying, and the first officer was the pilot monitoring.
During the climb to the planned cruising altitude of FL360, in accordance with standard procedures, the flight crew selected the standard atmospheric pressure of 1013 hPa on the altimeters.
The flight crew stated that, prior to commencing the descent for Kosrae, they obtained the weather and the local QNH. The weather had deteriorated from that forecast. The flight crew also stated that, during the descent and approach, the local flight information service radio operator provided a considerable number of weather updates on the local airport conditions at Kosrae. Visibility was around 3 NM, rain showers were in the area with low cloud and wind 'pretty much straight down the strip for (runway) 05'. The captain, as pilot flying, conducted the briefing for the non-directional beacon (NDB)/distance measuring equipment (DME) approach to runway 05. The captain stated that, at this time, they had made special mention of the unusually low transition level of FL 55. The captain stated that at most airports they operated into, the transition level was between FL 110 and FL 130. The crew then completed the descent checklist. They had decided that, based on the expected weather conditions, they would make two approach attempts, and if they could not land, would divert to Nauru Airport, the nominated alternate airport. Prior to descending below the transition level, the crew did not complete the approach checklist, which consisted of one item: set the altimeters to the local QNH and crosscheck them. Leaving the altimeters' subscale set to the standard atmospheric pressure setting of 1013 hPa, and not setting the subscale to the local barometric pressure of 1007 hPa, resulted in the indicated altitude over-reading, such that when the altimeter indicated 500 ft, the aircraft's actual altitude was about 320 ft above the mean sea level.
At about 08:56, the aircraft passed overhead the NDB at 5,000 ft, and continued the descent, tracking outbound on a heading of 300°, to about 10 NM from the NDB (10 DME). The flight crew were controlling the aircraft through the auto-flight systems, with an autopilot and the autothrottle engaged. At this point, the crew turned the aircraft left, and at 09:01, the aircraft intercepted the inbound track to the NDB at about 1,800 ft. The crew selected the landing gear down at 1,500 ft, and flap 15 at 1,250 ft.
The crew stated that they established visual contact with the runway as the aircraft passed through 900 ft indicated altitude, about 5 NM from the DME. At about 740 ft indicated altitude, the crew selected flap 25. The crew elected to delay selection of the nominated landing flap of 40 degrees until they made positive visual contact with the runway. They did not subsequently select flap 40 on that approach.
As the aircraft descended to the minimum descent altitude for the approach of 500 ft, the captain selected the altitude hold (ALT HOLD) mode to level the aircraft at 500 ft indicated altitude. At 09:03:13, an Enhanced Ground Proximity Warning System (EGPWS) Terrain Clearance Floor (TCF) alert sounded, and lasted for 5 seconds. The aircraft was over water, at 368 ft radio altitude. The crew reported that they were in visual meteorological conditions (VMC) at night, with the runway lights in sight. The crew stated that, at the time, they believed the EGPWS alert was due to a 'map shift' in the aircraft's navigation position. The flight crew selected 'terrain inhibit', which cancelled the current EGPWS TCF alert. The crew were not aware that the EGPWS had its own internal GPS.
At 09:03:19, the aircraft was at 4.31 DME, 480 ft indicated altitude and 340 ft radio altitude, and descending at about 313 fpm, when the EGPWS TCF alert again sounded, and lasted for 12 seconds. The aircraft maintained 480 ft indicated altitude for about 12 seconds, before descending again.
The crew reported losing visual reference with the runway when the aircraft was about 3 NM from the DME. In response to losing visual reference, the captain disconnected the autopilot and autothrottle and pressed the take-off/go-around (TOGA) switches on the thrust levers. At this time the recorded aircraft pitch angle was 9.5°. The flight data recorder data showed that TOGA was selected at 09:03:47, at 448 ft indicated altitude, or 304 ft radio altitude, and the aircraft was about 3.5 NM from the DME. At this time, the aircraft's computed airspeed reduced to 129 kt.
The captain stated that he pressed the TOGA switches on the thrust levers once. In the Flight Director engaged go-around mode, one TOGA switch press results in a reduced thrust autothrottle setting, and two presses of the TOGA switch advances the autothrottle to full go-around thrust. The crew stated that the aircraft pitch angle was initially raised to 15°, however, the captain observed the airspeed decay and pitched the aircraft down to increase the airspeed. The first officer stated he called 'sink rate' twice. The captain then realised and rectified the situation, depressing the TOGA switch a second time commanding full go-around thrust.
At 09:03:53, the aircraft was at 3.3 DME, and the third EGPWS TCF alert sounded, which lasted for 10 seconds. The aircraft was then at 384 ft indicated altitude, or 244 ft radio altitude, and descended 5 seconds later to its lowest radio altitude of 200 ft before climbing.
At 09:04:04, the flaps were retracted to 15° and the aircraft reached its maximum pitch up angle of 16°. Two seconds later, the flaps were retracted to 10°. From the time the captain set the thrust to TOGA until the aircraft was stabilised on the missed approach path (at about 09:05), the recorded aircraft pitch angle varied from -0.35° to +16°.
When the aircraft was established on the missed approach heading, the captain continued a climb to 4,000 ft. After stabilising the aircraft in the missed approach, the crew identified that the altimeters were still set to 1013 hPa and corrected them to the local area QNH. After repositioning overhead, the NDB at 4,000 ft, the crew then conducted a second approach and the aircraft landed at Kosrae without further incident.

Probable Cause:

Contributing factors
- The flight crew did not complete the approach checklist before commencing the non-precision NDB approach into Kosrae. As a result, the altimeters' barometric pressure settings remained at the standard setting of 1013 hPa instead of being set to the reported local barometric pressure of 1007 hPa. The flight crew descended the aircraft to the minimum descent altitude of 500 ft as indicated by the altimeters, however, due to the barometric pressure setting not being reset, the aircraft descended to a height significantly below 500 ft.
- The crew descended the aircraft in IMC and at night below the approach profile for the Kosrae runway, resulting in EGPWS alerts. Terrain clearance assurance was eroded further by the flight crew not correcting the flight profile until the flight crew lost visual contact with the runway.
- The flight crew's belief that the EGPWS warnings were due to a decreased navigational performance and not terrain proximity led to their decision to inhibit the first EGPWS warning and not correct the flight path.
- Due to the captain’s fatigue and the increased workload and stress associated with the inaugural regular public transport flight into Kosrae at night in rapidly deteriorating weather, the crew’s decision making and task execution on the missed approach were affected.

Accident investigation:

Investigating agency: ATSB (Australia)
Status: Investigation completed
Duration: 2 years and 9 months
Accident number: AO-2015-066
Download report: Final report

Insufficient rest / fatigue

Normal landing

Follow-up / safety actions

ATSB issued 1 Safety Recommendation

Show all...


photo of Boeing-737-33A-VH-NLK
Approach profile
photo of Boeing-737-33A-VH-NLK
Selected flight data recorder data plot

This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Majuro-Amata Kabua International Airport to Kosrae Airport as the crow flies is 934 km (583 miles).
Accident location: Exact; deduced from official accident report.

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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