What happened
On August 25, 1998, a pilot conducted a series of training flights using a winch-launch method from Samedan airfield. After two unsuccessful attempts to find sufficient thermal lift earlier in the afternoon, the pilot initiated a third takeoff at approximately 16:10 local time. The flight proceeded without any radio contact being established with the Samedan control tower or via the designated regional glider frequency.
At approximately 16:50, another glider pilot discovered the wreckage of the ASW 24, registration HB-3124, on the southwest slope of Piz Mezzaun in the Val Chamuera region. Emergency medical services arrived at the scene, but the pilot was found to have sustained fatal injuries. The aircraft was destroyed upon impact.
The investigation
Investigators examined the wreckage and the pilot's background. The pilot, a highly experienced retired airline captain with over 14,500 total flying hours, was found to have been in good health and was not under the influence of any substances at the time of the accident. The aircraft's weight and balance were within limits, and the flight controls and aileron kinematics showed no signs of mechanical failure.
Technical findings revealed that the aircraft's emergency locator transmitter (ELT) failed to activate during the crash, possibly due to a transport lock not being removed. The investigation also noted that the aircraft was not equipped with a barograph or GPS documentation system. The wreckage showed damage to the left wingtip consistent with ground contact, and the altimeter indicated an altitude of 2 ext{,}870 meters.
Findings
Analysis of the flight conditions suggests the pilot likely targeted the sun-exposed rock faces of Piz Mezzaun to find rising air. It is believed that the interaction between the prevailing north wind and the rising slope winds may have created windshear or convergence, leading to sudden and unexpected changes in lift and sink rates. This atmospheric instability likely caused the left wing of the HB-3124 to strike the terrain, resulting in a loss of control.
Safety action
The investigation concluded that the collision with the terrain was potentially caused by improper flight tactics when operating in mountainous terrain.