The Etha engines from Switzerland are almost certainly the very first expressions of the model compression ignition ("diesel") technology with which many of us are so familiar today. The engines were the work of Ernst Thalheim of Lausen in north-west Switzerland. In 1928 Thalheim obtained a Patent for the concept if a variable-compression self-ignition engine, proceeding thereafter to construct a wide variety of model and full-sized engines build upon this principle. Early examples at model sizes were rather heavy and bulky, but by around 1938 his designs had been brought to a point at which they had become suitable for use as model aircraft powerplants. At that point, they became more widely available to the public.
During this era, two main models were produced - the Etha 1 of 2.52 cc displacement and the far larger Etha 2 which packed a displacement of 8.25 cc. The Etha 1 was the more popular model for aero applications, evidently appearing in a number of distinct variants. At the 1941 Swiss National Champinships, 5 models powered by Etha engines went up against 11 rivals powered by the then recently-released Dyno 1. The Dyno had the better of this encounter, going on to become one of the most influential designs of the pioneering era, while the Etha engines faded relatively quickly.
A detailed article by Maris Dislers summarizing the history of the Etha range and including a test of an Etha 1 replica may be found elsewhere on this website.