What happened
On 17 October 2007, a Britten-Norman Islander BN2A-21, registration G-CHES, was performing a positioning flight from a temporary agricultural strip at Los Tomillares Ranch to a public runway in Guadalcanal, Seville. The flight was intended to be a short ferry operation between two unpaved fields.
During the takeoff roll, the aircraft achieved a positive rate of climb and cleared the end of the 400-meter runway. Shortly after liftoff, the right engine experienced a partial and transitory loss of power. This sudden drop in thrust caused the aircraft to yaw sharply to the right. The crew attempted to restore power by manipulating the fuel selector valves and transferring fuel supply. While they successfully recovered full power to the right engine, the sudden restoration of thrust—combined with the heavy left rudder input previously used to counteract the initial yaw—caused the aircraft to veer sharply to the left.
At a low altitude, the aircraft struck a hillside. The left wingtip made first contact with bushes, followed by the left landing gear and the forward fuselage. The impact resulted in one fatality and one serious injury among the crew.
The investigation
The CIAIAC examined the aircraft wreckage, the engines, and the fuel system. Investigators analyzed the Lycoming IO-540-K1B5 engines and the fuel samples taken from the main tanks. The investigation focused on whether a mechanical failure or fuel contamination caused the right engine's power fluctuation.
Engine and propeller inspections revealed no mechanical defects or maintenance irregularities. The ignition system and fuel pumps were found to be in good working order. However, laboratory analysis of the fuel from the left main tank revealed the presence of cloudy water and suspended solids. While the investigators could not definitively prove the exact source of the water, they considered both condensation in the tanks and contamination from the plastic drums used for refueling as likely origins.
Findings
- The aircraft was operating from a very short, uncompacted dirt runway, leaving a minimal margin for error during takeoff.
- The right engine experienced a transient power loss, likely due to water contamination in the fuel.
- The sudden recovery of power to the right engine, while the pilot was still applying significant left rudder to correct the initial yaw, created an uncontrollable asymmetric thrust condition.
- The aircraft's inability to maintain altitude and lateral control during this thrust oscillation led to the impact with the terrain.