What happened
On June 20, 2003, a SOCATA Rallye 235-C, registration EC-DRS, was conducting a flight for the purpose of pilot familiarization near the Casarrubios del Monte aerodrome in Toledo. The crew, consisting of a pilot in command and an experienced second pilot, had been performing a series of take-offs and landings on runway 0ob.
During the climb following the third landing, the aircraft experienced a sudden engine malfunction. The crew noted a "falter" in the engine, and the aircraft struggled to maintain climb performance, reaching a maximum speed of only 70 knots with a vertical speed of 200 to 300 feet per minute. In an attempt to maintain altitude, the crew extended the upwind leg and eventually attempted to increase speed by descending. However, the aircraft subsequently lost speed and altitude, impacting the ground. The impact was followed by a fire in the dry grass that spread to the aircraft, resulting in the near-total destruction of the airframe.
The investigation
The investigation focused on the engine's performance and the physical evidence at the crash site. Investigators examined the wreckage, noting that the propeller blades were bent in a manner suggesting the engine was not rotating at the moment of impact. A detailed workshop inspection of the Lycoming O-540-B4B5 engine revealed that while the oil and spark plugs were in good condition, the internal baffles (air deflector discs) within both mufflers had worked loose.
Investigators also analyzed the possibility of carburetor icing, but meteorological data from nearby Cuatro Vientos indicated temperatures and dew points that were not conducive to such an occurrence. The inspection of the engine components showed no other significant mechanical abnormalities that could account for the power loss.