What happened
On December 18, 2003, a PIPER PA-28-180, registration EC-BFO, was performing a general aviation flight from Valencia to Madrid-Cuatro Vientos. The pilot, an experienced flight instructor, had delayed the departure several times throughout the morning due to deteriorating weather conditions at the destination.
While cruising at FL080, the pilot encountered clouds and requested a lower flight level to maintain visual contact with the terrain. However, air traffic control denied the request because the aircraft was already near the minimum safety altitude for that specific sector. As the flight continued, the pilot reported difficulty maintaining altitude and noted the onset of ice formation on the wing leading edges, particularly on the left side, as well as ice accumulating on the windshield.
As the aircraft's performance degraded, the pilot declared an emergency. The aircraft began a descent through heavy cloud cover. The pilot eventually located a narrow, cleared farm road near Zarzuela, Cuenca, and performed an emergency landing. During the maneuver, the right wingtip struck an embankment, causing the aircraft to veer off the path into a field. The pilot sustained minor injuries, including a contusion and scratches, but was able to walk to a nearby town for assistance.
The investigation
The CIAIAC investigation examined the aircraft's maintenance records, the pilot's flight planning, and the meteorological conditions present during the flight. Investigators analyzed radar tracks, which showed the aircraft deviating from its planned airway and struggling to maintain altitude due to strong headwinds and icing.
Meteorological data revealed that the freezing level (isocero) was approximately 6,300 to 6,900 feet, meaning the aircraft was flying in temperatures highly conducive to ice formation. The investigation also noted that while the aircraft was authorized for IFR flight, it was not equipped to handle severe icing conditions. Physical evidence at the crash site, including large chunks of ice found on the ground behind the aircraft, confirmed the presence of heavy ice accumulation.
Findings
- The aircraft was flying at an altitude where temperatures and moisture levels were highly favorable for severe icing.
- The pilot was unable to descend to a safer altitude due to the mountainous terrain and the minimum altitude restrictions imposed by air traffic control.
- The accumulation of crystalline ice on the wing leading edges caused a significant degradation in aerodynamic performance and a loss of altitude.
- Communication between the pilot and air traffic control was hindered by the local topography, requiring another aircraft to act as a radio relay.
- The aircraft's flight plan had anticipated a cruise altitude of 9,000 feet, which would have placed the aircraft above the freezing level, but the actual flight path remained within the icing zone.