What happened
On June 1, 2001, a Grob Astir CS 77 glider, registration I-BZUM, was performing a local training flight via aero-tow. Upon releasing from the tow plane at approximately 1,000 meters, the glider encountered severe downward currents. These localized downdrafts caused a significant loss of altitude, making a return to the airfield impossible. Due to the proximity of mountainous terrain, the pilot was forced to perform an emergency landing in a wooded area. The impact with trees caused extensive damage, including a broken right wingtip, a torn left wing leading edge, and a destroyed canopy. The pilot escaped the wreckage uninjured.
On November 3, 2001, a Piper PA-34-200T aircraft, registration I-PREM, was conducting a commercial pilot training mission at Biella Airport. The flight involved simulated engine failure procedures. During the final approach, the crew attempted to extend the landing gear; however, the gear failed to deploy. The crew only realized the green gear-down lights were not illuminated during the final stages of the approach. Due to the low altitude and lack of margin for a go-around, the crew performed a belly landing. The aircraft sustained damage to the propellers, antennas, flaps, and fuselage. No injuries were reported among the two occupants.
The investigation
The ANSV examined the mechanical and operational circumstances of both events. For the glider accident, investigators analyzed the meteorological conditions, specifically the presence of Föhn winds, and the flight sequence following the tow release. For the Piper incident, the investigation focused on the landing gear extension mechanism and the crew's monitoring of cockpit indications. Post-accident inspections of I-PREM revealed that the emergency gear extension system functioned correctly, and the failure was traced to a specific component.
Findings
- The glider accident was caused by strong downward currents encountered immediately after tow release. A contributing factor was inadequate flight planning, as the pilot underestimated the intensity of the local downdrafts.
- The Piper incident was caused by a malfunction of the landing gear hydraulic pump, which prevented normal extension and locking. A contributing factor was poor coordination between the pilot and instructor, which resulted in a failure to notice the gear status in time to execute a go-around.