What happened
On August 30, 2008, a Robinson R44 helicopter, registration EC-IIX, was performing a low-altitude photography orbit near Monteagudo del Castillo, Teruel. The pilot was maneuvering the aircraft at approximately 100 feet above the ground, flying in a left-hand pattern with a diameter of roughly 350 meters to photograph a specific house. The weather conditions were clear and sunny with light winds.
During the second orbit, the pilot noticed the engine power increasing toward its maximum limit, as indicated by the manifold pressure gauge. In an attempt to manage the power, the pilot lowered the collective and then advanced the cyclic. The aircraft failed to respond adequately, and the pilot initiated an emergency landing in a nearby field. During the descent, the low rotor RPM warning light and siren activated, though the pilot had not previously noticed the drop in revolutions.
As the pilot approached the landing site, they attempted to clear a small ridge at the edge of the field by pulling up on the collective. This action caused the helicopter to lose remaining lift and strike the ground violently. The impact caused the landing skids to hit the ground first, followed by the main rotor blades striking the nose and tail boom, which subsequently broke apart. The engine continued to run after the impact, and the pilot successfully shut it down before all occupants evacuated.
The investigation
The CIAIAC examined the wreckage and the flight parameters. Investigators found that the engine and its components were functional, and the maintenance records were up to date. While a loose wire was found on one of the magnetos, it was determined that this likely occurred during the impact and would not have significantly reduced available power.
Technical analysis focused on the flight dynamics. The investigation established that the aircraft was operating at a high power demand due to the combination of high density altitude (approximately 5,000 ft), the weight of the aircraft, and the high load factor required for the tight turning radius. The investigation also examined the pilot's inputs relative to the manufacturer's safety warnings regarding rotor RPM management during high-altitude operations.
Findings
- The aircraft was operating at a high power demand due to the tight turning radius and the altitude.
- The pilot's decision to advance the cyclic after lowering the collective was contrary to manufacturer recommendations for maintaining airspeed and RPM.
- A loss of rotor RPM occurred because the power required for the maneuver exceeded the engine's available power.
- The pilot's final attempt to clear an obstacle by increasing collective pitch further depleted the remaining rotor RPM, leading to the uncontrolled descent.
- The high blade flapping observed during the impact was consistent with the low RPM conditions.