What happened
On June 26, 2019, a Piper PA25-235, registration HK-673, was performing agricultural spraying operations near the Santa Clara airfield in Villanueva, Casanare. While maneuvering over a crop approximately 5 km from the runway, the aircraft's engine suffered a sudden loss of power.
The pilot immediately responded by evacuating the chemical payload and following emergency procedures for engine failure. However, the engine failed to regain power. During the emergency descent, the pilot encountered an oil palm plantation and attempted a turn to avoid the trees. This maneuver caused the aircraft to enter a stall, resulting in an impact with the ground. The pilot survived the accident without injuries, though the aircraft sustained substantial damage, including destruction of the engine mount, engine, and airframe structure.
The investigation
An investigation by the GRIAA focused on the engine failure and the quality of the fuel used during the operation. Laboratory analysis of the fuel samples taken from the aircraft's supply revealed that the fuel was contaminated with 25% water and contained a low level of lead.
The investigation established that the fuel's chemical properties had been altered, likely due to the mixing of different fuel types in a single container. This contamination, combined with the heat generated during the high-workload agricultural flight, triggered a phenomenon known as "vapor lock." This occurred when the fuel vaporized within the carburetor system, interrupting the continuous flow of fuel to the engine.
Findings
- The primary cause of the engine power loss was fuel contamination with high water content and low lead levels, which induced vapor lock.
- The operator lacked clear organizational policies and procedures for the quality control, purchase, storage, and handling of fuel.
- Fuel storage conditions at the operational base were inadequate, leading to the presence of water and improper chemical concentrations in the fuel supply.
- The aircraft was airworthy and the pilot was fully qualified and current with all requirements.