Incident Overview

Date: Wednesday 12 April 2017
Aircraft Type: Cessna 208 Caravan I
Owner/operator: Spirit Avia Sentosa
Registration Number: PK-FSO
Location: 13 km N of Oksibil Airport (OKL) – ÿ Indonesia
Phase of Flight: En route
Status: Destroyed, written off
Casualties: Fatalities: 1 / Occupants: 1
Component Affected: Aircraft System (Specifically, GA-EGPWS – Ground-Based Electronic Ground Proximity Warning System) ? The lack of GA-EGPWS alert and warning system directly impacted the pilot’s ability to react to potential hazards and maintain situational awareness.Aircraft System (Specifically, GA-EGPWS – Ground-Based Electronic Ground Proximity Warning System) ? The lack of GA-EGPWS alert and warning system directly impacted the pilot’s ability to react to potential hazards and maintain situational awareness.
Investigating Agency: NTSCNTSC
Category: Accident
On October 26, 2023, a Cessna 208 aircraft, registered PK-FSO, experienced a significant incident while on a cargo flight from Tanahmerah Airport to Oksibil Airport in Papua, Indonesia. The aircraft departed at 11:44 hours local time, cruising at 7,000 feet, and was expected to arrive at Oksibil Airport at 12:24 hours. At 12:12, the aircraft passed another Cessna 208B aircraft, indicating a potential navigational issue. The pilot of the Cessna 208B, operating under the call sign PK-FSO, radioed that the aircraft was maintaining a direct route to Oksibil and advised to the Oksibil air traffic controller to contact the aircraft. The pilot failed to establish communication and did not arrive at the destination. After approximately 6 NM north of Oksibil, the aircraft was discovered on a ridge of Anem Mountain at a height of 7100 feet. The aircraft was severely damaged, and the pilot was fatally injured. Investigation revealed that the pilot had previously travelled on a night commercial flight the previous day, potentially leading to sleep disturbance and fatigue.On October 26, 2023, a Cessna 208 aircraft, registered PK-FSO, experienced a significant incident while on a cargo flight from Tanahmerah Airport to Oksibil Airport in Papua, Indonesia. The aircraft departed at 11:44 hours local time, cruising at 7,000 feet, and was expected to arrive at Oksibil Airport at 12:24 hours. At 12:12, the aircraft passed another Cessna 208B aircraft, indicating a potential navigational issue. The pilot of the Cessna 208B, operating under the call sign PK-FSO, radioed that the aircraft was maintaining a direct route to Oksibil and advised to the Oksibil air traffic controller to contact the aircraft. The pilot failed to establish communication and did not arrive at the destination. After approximately 6 NM north of Oksibil, the aircraft was discovered on a ridge of Anem Mountain at a height of 7100 feet. The aircraft was severely damaged, and the pilot was fatally injured. Investigation revealed that the pilot had previously travelled on a night commercial flight the previous day, potentially leading to sleep disturbance and fatigue.

Description

The Cessna 208 aircraft registered PK-FSO, was being operated on an unscheduled cargo flight from Tanahmerah Airport to Oksibil Airport in Papua, Indonesia. On board the aircraft was one pilot, 1,225 kg of general cargo and 800 lbs of fuel. At 11:44 hours local time, in daylight conditions, the aircraft departed Tanahmerah and cruised at altitude of 7,000 feet. Estimate time arrival at Oksibil would be 12:24. At 12:12, when the aircraft position was about 45 NM north of Tanahmerah, the aircraft passed another Cessna 208B aircraft from the opposite direction from Oksibil to Tanahmerah. The Cessna 208B pilot advised to the pilot via radio that the PK-FSO aircraft was in sight. The pilot responded that the aircraft was maintaining 7,000 feet on direct route to Oksibil. The pilot failed to contact the Oksibil air traffic controller and failed to arrive at the destination. The airline’s flight following officer received an emergency signal with a last recorded position of 6 NM north of Oksibil. The next day the aircraft was found on a ridge of Anem Mountain at a height of 7100 feet. The aircraft was destroyed by impact forces and the pilot was fatally injured. The investigation learned that two days prior the occurrence, the pilot travelled on a night commercial flight. This might have resulted in a sleep disturbance during the window of circadian low and an increase of the potential of fatigue. There are indications that the pilot did not have the required adequate restorative sleep before he started flying on the accident day. Prior to the occurrence flight, the pilot had flown for 3 flight sectors, with total flight hour of 2 hours 55 minutes. The multiple take-offs and landings that day increased fatigue. Based on the final flight track, the absence of voice communication, the weather condition permitting the pilot to identify the airport location and the aircraft wreckage, consistently indicated that there were no pilot activities to fly the aircraft after the last known pilot activities at about 29 Nm from Oksibil until impact. Colleagues of the pilot reported that he often smoked in the cockpit during the flight, looked sleepy and engaged the Terrain Inhibit switch which disabled the GA-EGPWS function while flying. This prevented any prior warning when the aircraft neared Anem Mountain. This known behavior was not reported to the Operation and Safety department, so no action could be taken. Contributing Factors: “The possibility of the pilot being fatigue, physical and environment condition increased pilot sleepiness which might have made the pilot inadvertently falling asleep indicated by no pilot activity. The absence of GA-EGPWS aural alert and warning was unable to wake up the pilot.”

Primary Cause

Possible sleep disturbance and fatigue, combined with insufficient restorative sleep prior to the flight, may have contributed to the pilot’s inattention and failure to communicate effectively.Possible sleep disturbance and fatigue, combined with insufficient restorative sleep prior to the flight, may have contributed to the pilot’s inattention and failure to communicate effectively.

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