What happened
On June 12, 1999, a pilot operating a Glaser-Dirks DG-400 motor glider, registration HB-2075, departed from Locarno-Magadino airport for a local flight. After preparing the aircraft with the assistance of another pilot, the pilot took off and initially flew toward the Brissago Islands. Data recovered from an onboard flight computer indicated that the engine was shut down approximately 11 minutes after takeoff at an altitude of 1,791 meters.
Following the engine shutdown, the aircraft continued in a gliding flight for roughly four minutes. During this period, the aircraft entered the Sassello-Cortasiell area. While attempting a maneuver near the ridge, the aircraft encountered a descending air current that had been noted by other glider pilots earlier that day. The aircraft struck the treetops, causing the right wing to detach and resulting in a fatal crash into the forest. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
Investigators examined the wreckage and recovered several critical pieces of equipment, including a Zander flight computer and a Garmin GPS. Analysis of the flight computer confirmed the timeline of the engine shutdown and the subsequent descent. The investigation also reviewed the pilot's preparations, noting that he had downloaded thermal forecasts prior to departure but had not sought updated local meteorological information from other pilots on site.
Technical inspections of the HB-2075 revealed several maintenance and equipment issues. The aircraft's annual inspections had not been recorded since March 1997. Additionally, the engine battery was insufficient for starting, requiring the use of a car battery, and the Emergency Locator Transmitter (ELT) was found to have an expired battery and irregular functionality. The investigation also noted that the pilot failed to follow local procedures by omitting the required radio announcement to the duty officer before takeoff.
Findings
- The primary cause of the accident was the loss of control of the glider following a collision with trees.
- The pilot likely encountered an unexpected descending air current while attempting a spiral maneuver near the ridge.
- Evidence suggested the pilot may have been experiencing significant tension or fatigue, evidenced by his rushed preparations and failure to check current local weather conditions.
- The aircraft was missing required annual inspections, and several safety-related components, including the ELT, were not in proper working order.