What happened
On 18 August 2002, a Grob G-103 «Twin Astir», registration D-8736, was performing a local training flight at the Aerodrome of Santa Cilia de Jaca in Huesca, Spain. The flight, operated by Club Navarra de Vuelo a Vela, was returning to base following a radio warning regarding deteriorating weather conditions and the potential for incoming storms.
As the aircraft was executing its landing pattern, the crew encountered significant wind conditions, including southerly gusts between 15 and 25 knots. During the transition from the base leg to the final leg of the approach, the pilot attempted a very tight leftward turn to avoid overshooting the runway threshold. This maneuver, combined with the atmospheric instability and wind gradient, led to a left wing stall. Due to the low altitude at which the stall occurred, the crew was unable to recover the aircraft before it impacted the ground to the right of the runway threshold. The impact destroyed the aircraft and resulted in one fatality (the pilot in the front cockpit) and one serious injury (the pilot in the rear cockpit).
The investigation
The CIAIAC investigation examined the aircraft's maintenance history, the meteorological conditions, and the flight crew's experience. The investigation confirmed that the aircraft was airworthy and had passed its annual inspection earlier that year. Investigators also reviewed the flight crew's recent experience, noting that both pilots had relatively limited flight hours in the twelve months preceding the accident.
Technical analysis of the wreckage revealed that the initial point of impact was the outer left wing. The investigation also considered the impact of the 90-degree crosswind on the high-aspect-ratio sailplane and the lack of a formal coordination procedure between the two pilots regarding critical flight phases, such as the use of air brakes.