NMAC -- ACR HAS AN NMAC WITH A LIGHT ACFT CLASSIFIED AS 'POP-UP' TFC DURING A SID OUT OF ORD.

Narrative

DEP ORD RWY 32L TWR GAVE US A TURN TO 090 DEG ON TKOF. ESTABLISHED ON 090 DEGS CLBING THROUGH 2800 FT MSL GOT TA NOTED TFC WAS 12 O'CLOCK MINUS 100 FT LESS THAN 1/2 MI. IMMEDIATELY INCREASED RATE OF CLB. RECEIVED RA AND CLBED DIRECTLY OVER TFC AT PLUS 300 FT. APCH WAS NOT AWARE OF TFC APPROXIMATE LOCATION WAS 3 MI ON THE 060 DEG RADIAL OF ORD VOR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE FLC WAS FLYING A B727-200 ON A SID THAT REQUIRES THE ACFT TO CLB SO STEEPLY THAT THE B727 HAS A HIGH DECK ANGLE. THIS HIGH DECK ANGLE MAKES IT DIFFICULT TO SEE OVER THE NOSE. THE FO SAID THAT WHEN THEY GOT THE 'TA' HE SHIFTED FORWARD IN HIS SEAT AND STRAINED TO SEE OVER THE NOSE OF THE ACFT. IN THIS POS HE SAW A LOW-WINGED; SINGLE ENG 'PIPER TYPE' OF ACFT AT LESS THAN A MI AT 12 O'CLOCK AT ABOUT THE SAME TIME THE 'RA' CAME. THIS ACFT WAS LESS THAN 100 FT BELOW THEM. THE FO CALLED THE TFC AND SAID 'PULL.' THE CAPT PITCHED UP AND THE FO ESTIMATES THAT THE MISS WAS LESS THAN 300 FT VERT AND '0' FT HORIZ. THE RPTR SAID THAT WHEN THE DEP CTLR WAS QUESTIONED ABOUT THE TFC HE WOULD NOT ANSWER INITIALLY; BUT FINALLY SAID THAT IT WAS 'POP UP TFC WITH NO ALT READOUT DSNDING TO 2500 FT.'