The hot exhaust plume flow characteristics under the action of helicopter rotor downwash were investigated based on numerical calculations.And the effects of rotor downwash velocity and exhaust direction on the infrared radiation characteristics of helicopter were analyzed.The results show that:under different exhaust directions

influences of rotor downwash on the hot exhaust plume differ a lot;when the hot exhaust is ejected upwards

the exhaust plume can come into collision with rear fuselage under the action of rotor downwash

leading to the rise of temperature of rear fuselage;when the exhaust is ejected upwards

the infrared radiation intensity of solid under rotor downwash velocity of 10m/s is larger than that without rotor downwash

the infrared radiation intensities show a gradual decreasing trend with the increase of rotor downwash velocity for oblique exhaust of 45° and sideward exhaust ways.The exhaust direction shows significant influence on the infrared radiation distribution.When the exhaust is ejected in oblique direction

the infrared radiation intensity detected from top direction is almost the same as that from lateral direction.While exhaust is ejected upwards or sidewards

strong infrared radiation occurs at some viewing directions.