What happened
On March 6, 2001, an Agusta Bell 206 BIII Jet Ranger, registration EC-DYQ, was performing agricultural spraying operations over a farm in Lorca, Murcia. During the second flight of the day, the pilot noticed a loss of engine power. Due to the low altitude required for the spraying task—approximately 40 to 50 cm above the crops—the pilot had insufficient altitude to recover rotor RPM and decided to perform an immediate ground landing on the same field.
As the helicopter's skids contacted the ground, they sank rapidly into the soft soil, causing a sudden deceleration. During this abrupt braking, the main rotor blades struck the tail rotor cone, resulting in the separation of the cone and the subsequent loss of the tail rotor. The aircraft came to a halt on its skids, and the pilot was uninjured.
The investigation
The investigation focused on the sequence of events leading to the impact and the condition of the propulsion system. Investigators examined the impact marks on the terrain and the distribution of debris. The tail rotor cone fragment was found almost directly beneath the site of the separation. The minimal ground marks left by the skids indicated that the yawing motion caused by the loss of the tail rotor was of low intensity.
Engine inspections and subsequent bench tests of the Allison 260-C20B engine revealed no mechanical abnormalities or malfunctions in the power plant. Analysis of the rotor dynamics suggested that the main rotor RPM must have been significantly reduced at the moment of the strike. The investigation concluded that the combination of low rotor RPM and the pilot's cyclic input during the landing caused the retreating blade to dip low enough to strike the tail cone.
Findings
- The primary cause of the incident was inadequate management of the throttle by the pilot, which led to a reduction in engine power and rotor RPM.
- The pilot's attention was likely focused on the precision required for the low-altitude spraying task, causing a lapse in monitoring critical engine and rotor RPM indicators.
- The soft terrain contributed to the sudden deceleration that facilitated the blade strike.