What happened
On September 22, 2015, a Schempp Hirth Duo Discus T glider, registration OH-888, was engaged in a private soaring flight near Santa Cilia de Jaca, Spain. After being towed to an altitude of approximately 1,630 meters, the aircraft began a continuous descent starting around 14:48 local time.
In an attempt to maintain altitude, the pilot deployed the retractable engine at approximately 14:56. However, the engine failed to start. As the aircraft continued to lose altitude, the pilot opted for an emergency landing in a field near Berdún. During the approach, the pilot attempted a landing to the right without turning into the wind. The right wing struck a group of trees approximately 3 meters high, causing the aircraft to rotate and lose control before impacting the ground. Both occupants, the pilot and a passenger, sustained minor injuries.
The investigation
The investigation analyzed flight data retrieved from the aircraft's FLARM collision avoidance system, which provided a precise reconstruction of the flight trajectory, altitude, and vertical speed. Investigators examined the engine's deployment sequence and the cockpit controls. The investigation confirmed that while the engine was physically extended from the fuselage, the ignition switch remained in the 'OFF' position. The investigation also reviewed the meteorological conditions, which were favorable for VFR flight, and the pilot's flight experience and documentation, all of which were found to be valid.
Findings
- The primary cause of the accident was the loss of control of the aircraft during the final phase of the landing due to the right wing striking trees.
- A significant contributing factor to the loss of altitude was the increased aerodynamic drag caused by the deployed engine, which was not functioning.
- The pilot failed to switch the ignition to the 'ON' position during the engine start checklist, likely due to an oversight.
- The pilot was misled by the sound and the rotation of the propeller (driven by airflow) into believing the engine was running.
- The aircraft sustained substantial damage, including fractures to the wing spars and fuselage breakage, though the cockpit integrity remained intact.