 On 12 April 1918, during its second flight of the acceptance program, a connecting rod broke in one of the rear engines.The Austro-Daimlers were replaced by four 300 hp Basse und Selve BuS.IVa engines and it was ready for further flight testing by 10 May 1918.The unproven Basse und Selves were also problematic and had a tendency to seize pistons, so they were in turn removed in favor of the less powerful but reliable 245 hp high-compression Maybach Mb.IVa.