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Design of winglets for the DG 300 glider

Abstract: Design of winglets for the DG 300 glider

 

In the framework of a project and a bachelor thesis, under the supervision of experts from the Centre for Aviation, a group of students designed, built and certified new winglets for a DG 300 glider.

Project Description

Scope of the bachelor thesis was to build and certify new winglets for a DG 300 sailplane. The basis was a student project by the same authors in which the aerodynamic shape was developed. The goal was achieved in three steps: first it was necessary to learn about the certification requirements and file an application for a Supplemental Type Certificate (STC) at EASA. Additionally, the structural loads on the winglets were calculated.

The next step was to actually build the winglets so that they would withstand the calculated loads. They were realised as carbon fibre half shells that were then glued together and fitted with an adapter kit.

The last step was dedicated to testing the new winglets. First of all, a static structural test was performed to demonstrate that the winglet could withstand a calculated maximum load of 393.3. The structure failed at a load of 1100 N. Thanks to this positive result it was possible to obtain a Permit to Fly from the swiss Federal Office for Civil Aviation (FOCA) and to perform the first test flight. The pilot commented positively on the improved lateral stability of the aircraft. Due to lack of time it was not possible to complete all required flight tests, therefore no STC has been obtained yet.

Impressions

The winglets were built at the ZHAW out of carbon fibre.
The winglet is installed on the test aircraft. The flow quality on the winglet could be judged during the test flight thanks to the white tufts.
The effect of winglets on flow quality was investigated by flight testing.

At a glance