FLT CREW OF HVT EXPERIENCES NMAC WITH HELI ON TKOF FROM SDF. HELI HAD BEEN CLRED TO CROSS OVER THE RWY 500 FT AGL AND THE LIGHT WT HVT ROTATED AND CLBED WITHIN 100 FT VERTLY BEFORE PERFORMING EVASIVE MANEUVERS.

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AS WE TAXIED FOR TKOF; WE WERE MONITORING THE TWR FREQ. TWR WAS GIVING A HELI INSTRUCTIONS FOR TRANSITIONING THE ATA. ATC CLRED THE HELI TO TRANSITION THE ATA S OF THE FIELD. THE CLRNC WAS THEN AMENDED TO: 'CROSS MIDFIELD AT 1000 FT; TFC A HVY DEPARTING RWY 17R.' A MIN OR SO LATER WE CALLED READY FOR DEP. WE WERE CLRED FOR TKOF ON THE RWY HEADING TO 5000 FT. THE TWR MADE NO MENTION OF THE HELI. AS WE STARTED THE TKOF ROLL; THE CAPT; WHO WAS THE PNF; NOTICED THE TCASII WAS SHOWING TFC JUST AHEAD AND TO THE L. IT WAS DIFFICULT TO TELL THE EXACT DISTANCE AND DIRECTION OF FLT AT THAT MOMENT. HE LOOKED OUTSIDE; BUT COULD NOT FIND IT. AS WE BROKE GND; THE CAPT CALLED TFC IN SIGHT DIRECTLY IN OUR FLT PATH. WE NOSED THE AIRPLANE OVER AT ABOUT 300 FT AGL. WE PASSED UNDER THE HELI AT ABOUT 400 FT AGL AND +200 KTS. THE HELI WAS FLYING AT 500 FT AGL. WE RPTED THE NEAR MISS TO TWR AND SWITCHED TO DEP. 1ST; WE THOUGHT THE TFC WAS AT 1000 FT AGL WHEN IN FACT IT WAS AT 1000 FT MSL. THE FIELD ELEVATION WAS 501 FT MSL. 2ND; WE WOULD NOT HAVE BEEN ALERTED TO THE TFC HAD IT NOT BEEN FOR THE TCASII DISPLAY AND US OVERHEARING THE TWR BEFORE WE CALLED READY FOR DEP. THE TWR SHOULD HAVE ADVISED US OF THE TFC BEFORE WE TOOK OFF; BUT THEY DID NOT. ALSO; WE WERE FLYING AN EMPTY AIRPLANE; THEREFORE WE ROTATED WAY BEFORE WE NORMALLY WOULD HAVE. THE TWR PROBABLY EXPECTED US TO USE THE NORMAL AMOUNT OF RWY FOR OUR TKOF ROLL.