Mercedes D IIIa aeroengine passes the modification test

The Mercedes D IIIa aeroengine, a derivative of the D III, passes the modification test in Berlin-Adlershof. The D IIIa and predecessor, of which some 12,000 units were produced in all, is the most built German aeroengine of the First World War. Officially, by war's end it has the reputation of being the most proven German aeroengine next to the Bz IV.