Glider enters unobserved stall during circling flight near Gerlitzen

Casualties unknown • auf der Gerlitzen, Gemeindegebiet Treffen am Ossiachersee, Kärnten, AT

A single-engine glider crashed into a forested area in Carinthia after the pilot entered an unobserved stall during a left-hand turn.

What happened

On July 14, 2013, at approximately 16:00 UTC, a Nimbus 3 glider departed from Feldkirchen airfield for a local flight. The flight path, reconstructed via GPS data logger, took the aircraft over the Ossiachersee and along the ridge of the Gerlitzen.

While operating near the Steinwender Hütte at an altitude of approximately 1,539 meters, the pilot performed two left-hand circles. Following a short straight flight, the pilot initiated another left turn. During this maneuver, the aircraft experienced a significant increase in sink rate, leading to a stall and subsequent impact with the forested terrain.

The investigation

The Austrian Federal Safety Investigation Board (SUB) examined the wreckage and analyzed data from the onboard GPS flight data logger. The investigation focused on the aircraft's flight parameters, including true airspeed and sink rate, during the final moments of the flight.

Investigators found that the aircraft's maintenance records were up to date and the aircraft was airworthy. The flight weight and center of gravity were within permissible limits. The investigation also reviewed the pilot's qualifications and medical status, finding no evidence of physical or psychological impairment, though the pilot had no memory of the final minutes preceding the impact.

Findings

  • The aircraft's airspeed during the circling maneuvers was between 65 km/h and 80 km/h.
  • The sink rate increased to as much as 5 m/s during the final left turn, at which point the aircraft was only about 100 meters above the ground.
  • The impact characteristics—specifically a shallow angle of impact combined with high sink rates and low forward velocity—indicated a stall.
  • The left wing initially struck the ground, causing the aircraft to rotate left, which subsequently led to the right wing striking a tree and separating from the fuselage.
  • While the local wind and thermal conditions were not specifically known, they may have influenced the flight dynamics.
  • The pilot failed to maintain sufficient airspeed to prevent an unobserved transition into a stall.

Probable cause

The accident was caused by a high angle of attack and low forward airspeed, resulting in the pilot entering an unobserved stall during a turning maneuver.

Frequently asked questions

What happened in the 2013-07-14 Nimbus-3 accident near auf der Gerlitzen, Gemeindegebiet Treffen am Ossiachersee, Kärnten, AT?

A single-engine glider crashed into a forested area in Carinthia after the pilot entered an unobserved stall during a left-hand turn.

What aircraft was involved and where did it happen?

The accident on 2013-07-14 involved a Nimbus-3, at auf der Gerlitzen, Gemeindegebiet Treffen am Ossiachersee, Kärnten, AT.

What was the probable cause of the accident?

The accident was caused by a high angle of attack and low forward airspeed, resulting in the pilot entering an unobserved stall during a turning maneuver.

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