Proposal for modification of the L-13 “blanik” sailplane’s wing hinge structural design

Abstract

As a result of a tragic accident in Southern Austria, all L-13 “Blanik” sailplanes were grounded. During this accident, the factory structural design failed, even though the plane underwent all mandatory inspections and repairs. The intention of this article is to introduce the possibilities of structural modification of this aircraft, specifically its wing beam and hinge. Already existing modifications are described, as well as new ones with the aim to strengthen its critical parts. Structural modification of the wing hinge and beam, replacement of rivet joints with stronger Hi-Loks and use of different hole angles to ensure a firmer joint and better stress distribution around these holes are covered. Last two beforementioned modifications are described in more detail, a tensile test is carried out and its results are compared to the results of the control samples. In the end, viability and practicability of these modifications are discussed.