What happened
On December 20, 2023, an Allied Ag Cat Productions, Inc. G-164, registration RP-R1423, was performing agricultural spraying operations in Maco, Davao de Oro. The aircraft, operated by South Pacific Aerial Spraying Services (SPASS), had taken off from the MEPI airstrip and was completing its second sortie of the day.
While executing a turn after finishing the fourth line of spraying at a banana plantation, the pilot noticed the engine began to sputter. Despite attempts to adjust the throttle to regain power, the engine continued to lose performance, causing the aircraft to descend. The pilot identified a potential landing spot in a nearby creek but, unable to determine the water depth, opted to perform a forced landing in a clearing within the plantation. During the descent, the aircraft's wings struck steel wires used in the plantation, and the aircraft settled in a ditch approximately five meters deep. The pilot sustained a minor injury involving a fractured hand, while the aircraft and at least twenty banana crops sustained substantial damage.
The investigation
The AAIIB investigation focused on the sudden loss of engine power. While the fuel itself was found to be free of contaminants, inspectors examined the carburetor filter and discovered it was heavily blackened and nearly opaque. Shaking the filter released a significant amount of fibrous residue.
Investigators determined that this debris likely originated from a chamois cloth used as a makeshift filter during the refueling process. While the operator's procedures included using a chamois for filtration, the investigation found no specific written criteria regarding when such a cloth should be replaced or how its serviceability should be determined.
Findings
- The primary cause of the accident was fuel starvation caused by a clogged fuel filter.
- Fibrous material from a chamois cloth used during refueling obstructed the carburetor filter, restricting fuel flow.
- The operator's Fuel Maintenance Policies and Procedures lacked defined criteria for the serviceability or lifespan of the chamois used during refueling.
- The pilot was properly licensed and the aircraft had valid airworthiness and registration certificates.