Active thermography to look beneath the surface of a historic German aircraft

Abstract

Thermography is a well-established non-destructive testing technique in materials research and defect detection. In addition, it is used on cultural heritage in the form of buildings and paintings. This contribution explores the utilisation of active thermography on an object of technical heritage – a historic aircraft of the Second World War, the Messerschmitt Me 163 b, as a part of an exhibition in the Deutsches Museum in Munich. Unfortunately, the appearances of many exhibits in museums have been altered before or during their time with the museum and are not in a historically accurate condition. Furthermore, the active service history is often not documented in detail or might have been lost. Both features are equally important in the presentation of information on a displayed item and destructive techniques cannot be employed on historic objects. Hence a non-destructive, non-contact way of examination was chosen in the form of thermography. With the help of phase analysis, flash thermography is also an invaluable tool for the evaluation of layered systems and can differentiate between paint layers. During the research presented herein, traces of abrasion and chemical stripping of older paint layers were visible. This complicates the compilation of sufficient information for a historically accurate restauration with any technique. Nonetheless, flash or pulsed thermography proves to be capable of finding not only identifying markings, defects, and different paint layers, but also the inner workings and substructure of the object under investigation.