What happened
On the morning of June 3, 2014, a Grumman Ag-Cat G164A, registered as RP-R5837, was performing a scheduled crop dusting mission from the MD Panabo Agri-Ventures Aerodrome in Panabo City. During the takeoff roll, the aircraft passed marker number 3 when the pilot heard an explosion, followed by the appearance of thick black smoke emanating from the engine. This event caused an immediate loss of engine power.
In response to the engine failure, the pilot attempted a rejected takeoff by reducing power and applying maximum braking. However, the aircraft's weight and the slippery surface of the runway prevented the pilot from maintaining control. The aircraft overran the runway, striking a perimeter fence at the end of the strip before coming to a rest in a canal approximately 20 meters beyond the runway boundary. The aircraft sustained significant damage to its engine, propeller, wings, and airframe. The pilot, who was the only person on board, escaped the wreckage without injury, and no fire occurred following the impact.
The investigation
The AAIIB investigation focused on the mechanical failure that triggered the engine power loss. Investigators examined the engine components and the maintenance history of the aircraft. The inquiry established that the engine suffered a structural failure during the takeoff roll. The investigation also looked into the maintenance practices regarding engine temperature monitoring and the adequacy of existing pre-flight and post-flight inspection protocols.
Findings
- The primary cause of the accident was the separation of the cylinder head from the cylinder barrel, which led to the sudden loss of engine power.
- Maintenance personnel had failed to replace the Cylinder Head Temperature (CHT) gauge, which is a critical instrument for monitoring engine health.
- There was a failure to follow the General Operating Instructions for R985 engines, specifically regarding prescribed temperature limits.
- Existing pre-flight and post-flight checklists were insufficient, as they did not require a visual inspection of the cylinder head cooling fins for exhaust deposits or emission stains.