G159 EXPERIENCED NMAC WITH C172 DEP FROM PARALLEL RWY AT VNY.

Narrative

WE WERE CLRED FOR TKOF ON VNY RWY 16R. WIND RPTED 110 DEGS AT 10 KTS. CESSNA HAD BEEN CLRED FOR TKOF ON RWY 16L; AND WE WERE ADVISED THE CESSNA WAS ADVISED WE WOULD BE TAKING OFF AND CLBING OFF HIS R SIDE. CESSNA TOOK OFF AS WE TAXIED INTO POS FOR TKOF. IMMEDIATELY AFTER TKOF; AFTER OUR INITIAL FLAP RETRACTION; I LOOKED UP FROM THE FLAP INDICATOR AND SAW US RAPIDLY OVERTAKING THE CESSNA; WHICH HAD BEEN BLOWN BY THE XWIND INTO OUR FLT PATH. AT THIS TIME; THE CESSNA WAS CO-ALT; ABOUT 300 FT AHEAD; AND VERY SLIGHTLY L OF THE NOSE. I CALLED 'WATCH THE CESSNA.' THE CAPT RAISED THE NOSE A LITTLE HIGHER; AND WE PASSED THE CESSNA VERY CLOSE ON HIS R; A LITTLE ABOVE HIS ALT. WE WERE EQUIPPED WITH TCASI; BUT GOT NO TA. ATC SHOULD CONSIDER THE EFFECT A XWIND MIGHT HAVE ON A LIGHT ACFT (WHICH IS MORE LIKELY TO MAKE AN INSUFFICIENT CORRECTION) BEFORE CLRING A HIGHER PERFORMANCE ACFT TO TAKE OFF ON A CLOSE PARALLEL RWY. AN OVERTAKE IS INEVITABLE; AND REDUCED MANEUVERABILITY AT LOW SPDS AND ALTS IN A HIGH PERFORMANCE ACFT MAKE COLLISION AVOIDANCE DIFFICULT; IF NECESSARY.