TCASII RA CREATES AN ALTDEV ALT EXCURSION BY PIC.

Narrative

WE WERE ON RADAR VECTORS TO FINAL AT NEWARK INTL (EWR) AND MAINTAINING A HDG OF 350 DEGS AT 8000 FT MSL. THE AUTOPLT WAS ENGAGED AND ALT HOLD WAS ON. APCH CTL ISSUED A TA AT OUR 12 O'CLOCK POS AND 5 MI. IT WAS A SMALL SINGLE ENG ACFT. I WAS THE COPLT AND WAS NOT FLYING THE ACFT. I ADVISED APCH CTL THAT I HAD NEGATIVE CONTACT ON THE ACFT BUT HAD A RETURN ON OUR TCASII. THE TCASII SHOWED AN ACFT AT THAT POS AND 600 FT ABOVE OUR ALT. A FEW MOMENTS LATER THE TCASII ISSUED A TA ON THE APCHING ACFT AND RESPONDED WITH AN AURAL 'TFC' ANNOUNCEMENT. IT WAS AT THAT TIME THAT I OBSERVED A SMALL ACFT SLIGHTLY ABOVE AND SLIGHTLY TO THE R OF OUR POS. I ADVISED APCH CTL THAT I HAD THE TFC IN SIGHT. A FEW SECONDS AFTER I ACQUIRED VISUAL CONTACT WITH THE ACFT; THE TCASII ANNOUNCED A SINGLE COMMAND 'CLB'. THE CAPT IMMEDIATELY ADVANCED THE THROTTLES; DISCONNECTED THE AUTOPLT AND BEGAN A CLB. I CONTINUED TO MAINTAIN VISUAL CONTACT WITH THE LIGHT ACFT UNTIL THE TCASII ANNOUNCED 'MONITOR VERT SPD'. AT THAT MOMENT I GLANCED DOWN AT MY VERT SPD INDICATOR AND SAW THAT WE WERE IN A HIGH RATE OF CLB; BUT THE VERT SPD INDICATOR 'FLY TO' ARC WAS COMPLETELY RED; AND WAS NOW COMMANDING A DSCNT. I REACQUIRED VISUAL CONTACT WITH THE OTHER ACFT AND SAW THAT IT WAS IN A L HAND BANK TURNING AWAY FROM US. OUR ALT WAS NOW AT 10000 FT MSL. A FEW SECONDS LATER THE TCASII ANNOUNCED 'CLR OF CONFLICT'. I RPTED TO APCH CTL THAT WE HAD A TCASII TA AND WERE RETURNING TO 8000 FT MSL.