Narrative:

Flying at 6000', a 120 degree vector with toronto approach control 125.4 preparing for a landing on runway 06R at cyyz, I as copilot observed a single engine (propeller), low wing civilian aircraft emerge from under me at approximately 300' going at a heading 20-30 degrees right of my heading. He was flying 140-150 degrees. Aircraft was a creamy, off-white, with a red over dark (probably black) trim stripes. No evasive action taken. I asked toronto approach if they had the aircraft that just went under us, and they said, 'no.' later approach said that the aircraft suddenly turned on its mode C and was indicating a descent out of 5000'. Our aircraft was about 210 KTS. The setting sun was at our back and the movement of the aircraft would have come from under the captain's side to my side (copilot's). I could have been more precise in describing the other aircraft, but since I realized that we were clear and that no evasive action was necessary, I was busy looking for other traffic and telling the captain what had happened. The other traffic did not appear to make evasive actions. We should have been more observant; even under radar control and talking to approach is no reason not to constantly clear for traffic. Our TCASII was MEL'd inoperative. Had it been operational... If the other aircraft was squawking, why didn't approach control see it, and why would its mode C suddenly come on? Requested approach control to follow the other aircraft and of our intent to file a near midair collision. The time from the near miss at 6000' and 120 degree heading until T/D at yyz runway 06R was 8 mins. I think approach control could have idented some form of traffic conflict or advisory for us, primary or secondary target.

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Original NASA ASRS Text

Title: ACR HAS NMAC WITH SMA WITHIN THE TCA.

Narrative: FLYING AT 6000', A 120 DEG VECTOR WITH TORONTO APCH CTL 125.4 PREPARING FOR A LNDG ON RWY 06R AT CYYZ, I AS COPLT OBSERVED A SINGLE ENG (PROP), LOW WING CIVILIAN ACFT EMERGE FROM UNDER ME AT APPROX 300' GOING AT A HDG 20-30 DEGS RIGHT OF MY HDG. HE WAS FLYING 140-150 DEGS. ACFT WAS A CREAMY, OFF-WHITE, WITH A RED OVER DARK (PROBABLY BLACK) TRIM STRIPES. NO EVASIVE ACTION TAKEN. I ASKED TORONTO APCH IF THEY HAD THE ACFT THAT JUST WENT UNDER US, AND THEY SAID, 'NO.' LATER APCH SAID THAT THE ACFT SUDDENLY TURNED ON ITS MODE C AND WAS INDICATING A DSNT OUT OF 5000'. OUR ACFT WAS ABOUT 210 KTS. THE SETTING SUN WAS AT OUR BACK AND THE MOVEMENT OF THE ACFT WOULD HAVE COME FROM UNDER THE CAPT'S SIDE TO MY SIDE (COPLT'S). I COULD HAVE BEEN MORE PRECISE IN DESCRIBING THE OTHER ACFT, BUT SINCE I REALIZED THAT WE WERE CLR AND THAT NO EVASIVE ACTION WAS NECESSARY, I WAS BUSY LOOKING FOR OTHER TFC AND TELLING THE CAPT WHAT HAD HAPPENED. THE OTHER TFC DID NOT APPEAR TO MAKE EVASIVE ACTIONS. WE SHOULD HAVE BEEN MORE OBSERVANT; EVEN UNDER RADAR CTL AND TALKING TO APCH IS NO REASON NOT TO CONSTANTLY CLR FOR TFC. OUR TCASII WAS MEL'D INOP. HAD IT BEEN OPERATIONAL... IF THE OTHER ACFT WAS SQUAWKING, WHY DIDN'T APCH CTL SEE IT, AND WHY WOULD ITS MODE C SUDDENLY COME ON? REQUESTED APCH CTL TO FOLLOW THE OTHER ACFT AND OF OUR INTENT TO FILE A NMAC. THE TIME FROM THE NEAR MISS AT 6000' AND 120 DEG HDG UNTIL T/D AT YYZ RWY 06R WAS 8 MINS. I THINK APCH CTL COULD HAVE IDENTED SOME FORM OF TFC CONFLICT OR ADVISORY FOR US, PRIMARY OR SECONDARY TARGET.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.