In flight simulation detailed knowledge of human motion perception is crucial. Phase differences between inertial and visual motion introduced by motion filters might have negative effects on the fidelity of flight simulation. This study investigated human visualvestibular phase-error detection. An experiment was conducted to measure the maximum amount of phase lead of the inertial motion with respect to the visual motion that remains undetected by the human. It contributes to the assessment of so-called coherence zones investigated in previous studies. Possible effects of the stimulus frequency, amplitude and the axis of rotation were examined. They were found to have no significant influence on phase-error detection. The average phase-error threshold was determined at 22 degrees. In accordance to previous studies the results showed that humans can be considered more like phase-error detectors rather than time delay detectors.