ACR B727 HAS NMAC WITH C172 DURING INITIAL CLB. SIMULTANEOUS DEPS; MULTIPLE RWY OP INTERSECTING RWYS. ACR FLC EXPERIENCED VISUAL INTERFERENCE ON XING TFC. TFC SIGHTED EVASIVE ACTION LEVELOFF. SEE AND AVOID CONCEPT WORKED.

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FLT BHM-ATL TAXI OUT NORMAL. NOTIFIED TWR READY TO DEPART FROM RWY 5. TWR RPTED TFC 4 MI OUT FOR RWY 5 AND CLRED OUR FLT FOR TKOF RWY 5. WITHOUT DELAY; CAPT ADDED PWR TO MOVE THE ACFT ONTO THE RWY AND CALLED FOR THE FINAL ITEMS ON THE BEFORE TKOF CHKLIST. WITHOUT STOPPING IN POS; CAPT SET TKOF PWR WHEN THE ACFT WAS LINED UP AND READY. WELL INTO THE TKOF ROLL; I HEARD TWR CLR AN ACFT TO DEPART RWY 36. AT THAT MOMENT I REPEATED WHAT I HEARD TO THE CAPT. AIRSPD ABOUT 100-110 KTS. AFTER THE V1 VR CALL; THE CAPT ROTATED THE ACFT. IT WAS ABOUT THAT TIME I FIRST SAW THE CESSNA CLBING ABOVE THE ARPT BUILDINGS BTWN RWY 5 AND RWY 36. IT WAS IMMEDIATELY CLR WE HAD A CONFLICT. I POINTED OUT THE TFC AND MOTIONED WITH MY HAND FOR THE CAPT TO KEEP THE NOSE DOWN; OUR ACFT WAS AT ABOUT 50 FT. WE DID NOT RAISE THE GEAR AND WITH MY COACHING; CAPT HELD OUR CLB TO LESS THAN 100 FPM. THE 2 ACFT CONVERGED ON THE RWY INTXN AT THE SAME TIME. CESSNA 172 ALT 500-600 FT ESTIMATED. OUT FLT ALT ABOUT 200 FT ESTIMATED. LATERAL DISTANCE LESS THAN 100 FT. OUR ACTION: SIGNIFICANT REDUCTION IN TKOF CLB TO AVOID MIDAIR. PROBLEM AROSE: TWR PERSONNEL OPERROR. CONTRIBUTING FACTORS: INTERSECTING RWYS. PLT VIEW OBSTRUCTED BY ARPT BUILDINGS. THE CREW OF ACR FLT BECAME INTERESTED BUT NOT ALARMED AT THE CLRNC FOR THE CESSNA TO TKOF RWY 36. CERTAINLY NOT ENOUGH TO ABORT AT HIGH SPD. WHY? BECAUSE TWRS; EVERYWHERE; WILL GRANT TKOF CLRNC TO ACFT ON TXWYS -- SOMETIMES 2-3 MINS FROM THE RWY. SUPPLEMENTAL INFO FROM ACN 340579: HE TOOK NO OBVIOUS EVASIVE ACTION. WE SIGNIFICANTLY DECREASED OUR AFTER LIFTOFF CLB RATE WHICH PERMITTED THE CESSNA TO FLY DIRECTLY OVER US. IF WE HAD NOT SEEN EACH OTHER (NO ADVISORY OR DIRECTION WAS GIVEN BY THE CTL TWR) THE CESSNA WOULD HAVE FLOWN THROUGH OUR VORTICES/JET WASH IMMEDIATELY BEHIND US.