What happened
On 17 December 2022, a Thrush S2R-T34, registration PK-PND, was conducting aerial fertilizer topdressing operations over a palm oil plantation near Kajui Airstrip, Indonesia. The aircraft was being operated by PT Sinar Mas Super Air (SMSA) during the afternoon flight shift.
Prior to the accident, the aircraft had undergone maintenance to replace left brake pads and adjustments to the tail wheel. During the afternoon shift, the pilot had completed two successful sorties. However, during the takeoff roll for the third sortie, the aircraft began its roll on the left side of the runway with the left wheel already touching the grass shoulder.
As the pilot applied power, the aircraft failed to respond to steering inputs and continued straight, drifting further onto the grass. At approximately 610 meters into the takeoff roll, the aircraft experienced a sudden movement. In an attempt to reduce weight and assist ascent, the pilot attempted to dump the fertilizer load, but the aircraft subsequently rolled over and came to rest in an upside-down position. The pilot sustained minor injuries.
The investigation
An investigation by the KNKT established that the aircraft's mass and center of gravity were within permissible limits, and the weather conditions were clear with calm winds. The investigation examined the aircraft's technical history, noting that while the left brake pads had been replaced earlier that day, the pilot had reported a lack of grip in the left brake during a previous taxi maneuver.
Investigators also reviewed the operational procedures, noting that the pilot had not set the flaps prior to the takeoff roll, intending to do so later if necessary. Furthermore, the investigation found that the tail wheel issue reported during the shift change had not been documented in the Aircraft Maintenance Log, and no formal Operational Flight Plan had been prepared for the flight.
Findings
- The aircraft was positioned on the left side of the runway with the left wheel on the grass prior to the start of the takeoff roll.
- The aircraft failed to respond to rudder and brake steering inputs, continuing straight despite increased power.
- The pilot did not set the flaps according to the Airplane Flight Manual (AFM) requirements prior to the takeoff roll.
- There was a lack of standardized procedures for managing runway excursions or maintaining takeoff centerline positioning.
- Maintenance discrepancies, specifically regarding the tail wheel, were not recorded in the official technical logs.
Safety action
Following the incident, SMSA implemented a Temporary Emergency Procedure for pilots to follow if an aircraft veers off the runway. The company also issued a pilot notice emphasizing the necessity of maintaining the runway centerline during the start of the takeoff roll. The KNKT has recommended that the operator implement more robust operational control systems, ensure strict adherence to maintenance reporting, and enforce proper takeoff configuration procedures.