POTENTIAL CONFLICT BTWN CLBING TFC; AN A320 AND A TWIN OTTER ALLEGEDLY ENGAGING IN PARACHUTE JUMPING ACTIVITY.

Narrative

ATIS ADVISED PARACHUTE JUMPING IN EFFECT N OF PTW 13500 FT AND BELOW. CAPT AND I BRIEFLY DISCUSSED THIS ITEM. OUR RTE OF FLT WAS DIRECT PTW; PTW 320 DEG RADIAL TO J64; RAV. AFTER BEING TURNED OVER TO ZNY JUST NW OF PTW AND OUT OF 10000 FT MSL; WE WERE CLRED TO 17000 FT MSL. HEARD A CALL SIGN ON FREQ SAY 30 SECONDS TO JUMP; OR SOMETHING TO THAT EFFECT. ABOUT THAT TIME I VISUALLY ACQUIRED A TARGET AT 12 O'CLOCK AT OUR ALT. WE WERE CLBING 2000 FPM. ALMOST SIMULTANEOUSLY WE GOT A TCASII TA WHICH SHOWED 12 O'CLOCK TFC AT ABOUT 3 MI AND 100 FT ABOVE US AND CLBING. WHEN THE DISPLAY SHOWED US PASSING THROUGH HIS ALT (WE WERE AT ABOUT 13000 FT NOW); WE GOT A 'DSND NOW' RA. I HAD THE TARGET VISUALLY AND THIS LOOKED LIKE A VERY BAD CHOICE (TO DSND NOW). THE CAPT COMMANDED A DSCNT. I REACHED TO CLICK OFF THE AUTOPLT AND THE TCASII COMMANDED 'CLB NOW.' I ESTIMATE ALL OF THIS OCCURRED IN LESS THAN 5 SECONDS. (5 SECONDS FROM INITIAL RA; TO CAPT COMMAND; TO SECOND; DIFFERENT RA.) BY NOW I WAS MANUALLY CTLING THE AIRPLANE AND WE CLBED WELL CLR OF THE TARGET AT APPROX 4000 FPM. WE RPTED RA TO CTR. NO ATC CLRNCS WERE VIOLATED. BASED ON MY VISUAL REFS; THIS WAS NOT A REAL SERIOUS CONFLICT. I HAD VISUAL CONTACT AT ALL TIMES AND SAW NO POSSIBILITY OF COLLISION. HOWEVER; THE TCASII REALLY SCARED ME. BASED ON MY EXPERIENCE WITH THIS AIRPLANE (A320); COMPLIANCE WITH THE INITIAL RA WOULD HAVE REQUIRED AT LEAST 500 VERT FT TO GET TURNED AROUND. THIS WOULD HAVE REALLY PUT US IN CLOSE PROX TO THE TARGET (WHICH; BY THE WAY; APPEARED TO BE THE JUMP AIRPLANE; A TWIN OTTER). FURTHERMORE; IF THE JUMPERS HAD GONE OUT AS WE WENT BY UNDERNEATH; THIS WOULD BE A MUCH DIFFERENT RPT. 'CLB; XING CLB' WOULD HAVE BEEN A MORE APPROPRIATE INITIAL RA. QUESTION: WHY WAS THE JUMP AIRPLANE ON (RIGHT ON) A STANDARD TURBOJET PHL DEP RTE? QUESTION: WHY DIDN'T WE GET AN ADVISORY FROM ATC? (AT LEAST I DON'T THINK WE DID. HE WAS WORKING BOTH OF US). QUESTION: WHY DID IT TAKE ME SO LONG TO REACT? 5 SECONDS SEEMS AN ETERNITY IN THAT SIT.