To determine the effect of ground vortices on the performance of the propeller, the **data** at two height ratios are compared, namely, h=R ¼ 3:0 and h=R ¼ 1:46. The height ratio of h=R ¼ 3:0 is the maximum height ratio could be achieved in the setup. It is supposed that the strength of ground vortices generated at the height ratio of h=R ¼ 3:0 is much smaller than that at h=R ¼ 1:46. The height ratio of h=R ¼ 1:46 is the position closest to the ground during our test, and it induces ground vortices which have the strongest impact on the propeller inflow. The difference of the propeller performance between h=R ¼ 1:46 and h=R ¼ 3:0 is negligible, as shown in Fig. 17. This means that the time-averaged performance of the propeller is independent of the ground vortices. First, the effects of the vortices entering the propeller in the propeller axial direction are cancelled out by each other. This hypothesis is confirmed by the tangential velocity distribution, as shown in the top right of Fig. 12. Second, although the effect of vortices entering the propeller in the radial direction induces an axial velocity decrease in the propeller inflow (as shown in the top left of Fig. 12), this influenced region is small compared with the whole disk region of the propeller and its effect is negligible as well. As the majority of research on turbofans is conducted on suction tubes, the impact of ground vortices on the loadings of a turbofan is not available. Our tests on a propeller give such **data** for the first time.