Blaník Wing Modification

• CS-22 STC
• Regaining Airworthiness

AD&C background:

• Design and Certification
• 2011

The project:

With over 3000 gliders built since 1956, the Blaník L13 is the most produced glider worldwide.
In June of 2010, a fatal accident in Austria resulted in the worldwide grounding of the entire active L13 and L13A fleet. The reason for this grounding was to a large extent the suspicion of premature fatigue in the load path of the main wing spar. AD&C assumed the laborious task of putting this historic glider back in the air.

This task consisted of:

• Reconstruction of the 3D geometry of the aircraft, in particular the area of the main wing spar;
• Load path analysis;
• Verification by elaborate FEM calculations;
• Fatigue life investigation;
• Crack propagation calculations;
• Definition of useful life with and without (undetected) damage;
• Design of structural modification aimed at:
  • reducing the stress levels, and therefore increasing the useful life;
  • Facilitating the inspectability of critical areas;
• Definition of an inspection program, using NDT (Non destructive testing) techniques to periodically assess the state of the aircraft's critical areas.