Introduction
On 12 September 2012, a Thrush T34 agricultural aircraft, registration PK-PNO, operated by PT. Sinar Mas Super Air, was involved in a serious incident during landing at Ujung Tanjung Airstrip, Riau, Indonesia. The aircraft had departed from the same airstrip earlier that morning for a flight to Nagamas Airstrip but returned due to low cloud conditions. No persons were injured in the occurrence.
Factual Information
The aircraft departed Ujung Tanjung Airstrip at 0005 UTC (0705 LT) with destination weather reported as hazy. En route, the pilot encountered low cloud along the flight path. Upon reaching Nagamas Airstrip, the runway was not visible, and the pilot decided to return to Ujung Tanjung. Approaching the departure airstrip, the pilot observed wind from the wind sock at approximately 7 to 10 knots from the southeast, and motorcycles moving along the runway edge. The pilot categorized the conditions as normal and proceeded to land.
During the landing, the aircraft experienced a hard landing and bounced. Subsequently, during the landing roll, it veered to the left, coming to rest in a ditch approximately 21 meters left of the runway edge beneath palm trees, with the tail pointing upward. The right main landing gear was displaced upward and rearward, the propeller blades were bent rearward, and the outer upper right wing sustained a heavy dent.
The runway surface at Ujung Tanjung was grass and slippery when wet. At approximately the halfway point of the runway, there was an access crossing road with a step of more than five centimeters, and a free-access road ran along the runway edge. The investigation noted that the hazard identification and risk assessment required by the operator's Aircraft Operation Manual were not found.
The pilot was certified and qualified in accordance with Indonesian regulations. The aircraft was certified and airworthy. No safety actions were reported at the time of the final report.
Analysis
The analysis focused on weather conditions and the pilot's decision to return and land. The en-route weather featured low cloud, consistent with the Inter Tropical Convergence Zone (ITCZ) affecting Sumatra in September, which brings moist air and cloud formation, often in the morning. The pilot's workload likely increased due to flying in marginal weather combined with potential hazards near the runway, such as the motorcycles and the uneven crossing road, which may have affected approach and landing performance.
Conclusions and Contributing Factors
The investigation identified contributing factors to the incident:
- The pilot departed without obtaining adequate weather information and sources, and the en-route weather included low cloud.
- The pilot's workload increased as a result of flying in marginal weather while facing potential hazards near the runway.
No probable cause was explicitly stated; the contributing factors are considered to have played a role in the sequence of events.