What happened
On August 21, 2002, a Grob G 103 A Twin II Acro glider, registration EC-DPH, was conducting a long-duration mountain navigation training flight. The flight originated from the Santo Tomé del Puerto aerodrome in Segovia. The crew consisted of an instructor in the rear seat and a student in the front seat.
During the return leg, the aircraft experienced a loss of altitude due to the presence of approaching storms. To avoid the weather, the crew decided to perform an off-field landing at a location known as Prado Cerrado, near the town of Montejo de Tiermes. During the approach phase, the aircraft struck high-voltage power lines at an altitude of approximately 5 to 7 meters. The impact caused the cockpit canopy to shatter and resulted in significant damage to the left wing and fuselage. The aircraft subsequently impacted the ground; however, the impact with the terrain was relatively soft, likely because one of the utility poles was knocked down by the initial strike, which helped cushion the descent.
The investigation
The investigation focused on the sequence of events leading to the contact with the electrical infrastructure. Investigators examined the damage to the EC-DPH, noting that the left wing's leading edge was torn and the left airbrake was ripped from its housing. The fuselage was split along approximately three-quarters of its length.
Witnesses and crew statements indicated that while the student pilot noticed the utility poles, the instructor believed the aircraft could safely pass between them. The investigation also assessed the impact on the electrical grid, which saw 700 meters of cable, 12 insulators, and 5 crossarms damaged, causing power outages in several nearby towns.
Findings
- The primary cause of the accident was the impact with high-voltage cables during the landing approach.
- The crew's decision to perform an off-field landing was driven by a loss of altitude and deteriorating weather conditions (storms).
- The altitude during the approach was likely too low to allow for the selection of a safer landing site.
- While the utility poles were visible to the crew, the thin high-voltage cables were not detected.
- The instructor sustained head injuries due to the destruction of the rear canopy glass, while the student remained uninjured.
- The collapse of a support pole during the initial strike mitigated the severity of the subsequent ground impact.