Experimental diagnostic study has been performed

and results show that the downwash flow had remark able impacts on the aerodynamic performances

characteristic temperatures

and infrared radiation.With the increase in the downwash flow velocity

the entrainment coefficient decreased

and the exhaust flow temperature increased

resulting in the rapid increases of the exhausting duct temperature and the suppressor surface temperature.And finally

the downwash flow at hovering condition caused an increase of total infrared radiation between 3～5 μm by about 35%.