 Her "U-Bootsabnahmekommission" trials (UAK, "U-Boats Acceptance Commission") at Kiel was delayed by three weeks because of the number of U-boats already there, so she remained at Flensburg, performing exercises.The U-boat finally arrived at Kiel on about 21 April, taking the normal UAK trials in Kiel Fjord.She also entered the pressure dock at the Deutsche Werke shipyard and was tested to the equivalent depth of .