What aircraft was involved and where did it happen?

The accident on 2006-11-29 involved a aircraft, at Mattsies, DE.

What was the probable cause of the accident?

The aircraft suffered a catastrophic loss of control due to the disintegration of the horizontal stabilizer caused by aerodynamic flutter.

Grob G 180A Structural Failure During Demonstration Flight

A Grob G 180A experienced a catastrophic horizontal stabilizer failure due to flutter during a demonstration flight near Mattsies, resulting in the pilot's death.

What happened

On November 29, 2006, at 13:12 local time, a Grob G 180A departed from the Mindelheim-Mattsies airfield to perform a demonstration flight for a visiting group. The flight was intended to showcase the aircraft's performance by flying over the airfield.

While the aircraft was maneuvering to fly over the airfield after passing the town of Tussenhausen, components of the horizontal stabilizer detached. This structural failure caused the aircraft to enter a high-rate descent, and it impacted a field approximately 1,500 meters southeast of the airfield at 13:15. The impact resulted in the destruction of the aircraft and the fatal injury of the pilot.

The investigation

The BFU investigation focused on the structural integrity of the tail unit and the aerodynamic conditions during the flight. Investigators examined the wreckage for evidence of structural failure, specifically looking for signs of flutter or fatigue. The investigation also reviewed the aircraft's certification basis, including the stability and flutter-free proofs provided during its design phase.

Due to the lack of available flight data and the limited scope of the investigation, the investigators could not definitively determine the exact environmental or operational conditions that triggered the flutter. However, the investigation looked into several possibilities, including the potential loosening of previously installed balance masses and whether structural damage at the junction between the elevator horn and the elevator surface had reduced the critical flutter speed.

Findings

The primary cause of the accident was the structural disintegration of the horizontal stabilizer caused by flutter, which rendered the aircraft uncontrollable.
The investigation could not establish the specific circumstances that led to the onset of the flutter event due to a lack of flight data.
It could not be ruled out that the failure of the bond between previously installed balance masses contributed to the event.
There was a possibility that insufficient structural dimensioning or strength calculations at the elevator-to-surface transition reduced the aircraft's critical flutter speed.
The aircraft was in a clean configuration (landing gear retracted and flaps up) for the planned high-speed flyover at the time of the failure.