Narrative:

I crossed the path of air carrier flight, an large transport, inbound for ewr, nj, the airport which I had departed from just 20 mins earlier. A pilot on that aircraft had reported a 'near miss' to the controller indicating a separation of 200 ft vertically according to his TCASII. The meteorological conditions were VFR clear with no ceiling and 25 to 30 mi visibility. The altimeter setting was 30.73 and, at my altitude of 6500 ft MSL, the pressure altitude was 5750 ft. The temperature at altitude was 1 degree C. I was headed to dca on a VFR flight plan. I was level at 6500 ft MSL talking to ny approach on frequency 128.55. I was receiving vectors to the robbinsville VORTAC, my first waypoint on this trip. I knew there would be opposite inbound traffic for ewr coming towards me due to the runways in use at ewr -- those being 4L and 4R. Knowing my position from flying in the area lot, I kept particular attention outside the cockpit for traffic and spotted this particular aircraft before the controller even called it out to me. I responded with a tally-ho and had a visual on him the entire time. When our paths crossed, my best judgement would say 500 ft separation vertically, which is what it was supposed to be. The air carrier was at 6000 ft MSL. Our position was 5 DME northeast of rbv VORTAC off the 035 degree radial. After we passed each other, a pilot of air carrier flight said 'that small aircraft we just passed was not at 6500 ft and I'm reporting a near miss. Can I have his tail number?' the controller responded with 'what is the request for?' the pilot said 'my TCASII is indicating a separation of 200 ft and I need to file a report.' the controller obliged and gave my tail number. At this time, I immediately said 'that is a negative! My altitude is 6500 ft and the altimeter is 30.73.' the controller responded to say I had done nothing wrong and my mode C was showing 6500 ft. I called her once I got on the ground at dca and spoke to the shift supervisor. He told me too worry and if I received any calls to refer them to mr X. The working controller was Y. The reason I am submitting this report is to bring up a couple of issues. One being the actual accuracy of TCASII, the pilot's reliability upon this equipment instead of his own eyes, especially in the excellent visibility we had, his judgement on our actual separation, and his accusation right on the radio! I have almost 550 hours total time with multi-engine private. I would never accuse so quickly over the federal air waves. He is supposed to be 'professional' and probably has at least 2500 hours total time. I would like some feedback on the issue of TCASII, how much the PIC should rely on it in VMC when he should looking outside, instead of playing video games on a first generation piece of equipment.

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Original NASA ASRS Text

Title: SMA PLT QUESTIONS MODE C ERROR LIMITS. ACR CLAIMS CLOSE PROX WHEN ATC SAYS MODE C SHOWS 500 FT.

Narrative: I CROSSED THE PATH OF ACR FLT, AN LGT, INBOUND FOR EWR, NJ, THE ARPT WHICH I HAD DEPARTED FROM JUST 20 MINS EARLIER. A PLT ON THAT ACFT HAD RPTED A 'NEAR MISS' TO THE CTLR INDICATING A SEPARATION OF 200 FT VERTICALLY ACCORDING TO HIS TCASII. THE METEOROLOGICAL CONDITIONS WERE VFR CLR WITH NO CEILING AND 25 TO 30 MI VISIBILITY. THE ALTIMETER SETTING WAS 30.73 AND, AT MY ALT OF 6500 FT MSL, THE PRESSURE ALT WAS 5750 FT. THE TEMP AT ALT WAS 1 DEG C. I WAS HEADED TO DCA ON A VFR FLT PLAN. I WAS LEVEL AT 6500 FT MSL TALKING TO NY APCH ON FREQ 128.55. I WAS RECEIVING VECTORS TO THE ROBBINSVILLE VORTAC, MY FIRST WAYPOINT ON THIS TRIP. I KNEW THERE WOULD BE OPPOSITE INBOUND TFC FOR EWR COMING TOWARDS ME DUE TO THE RWYS IN USE AT EWR -- THOSE BEING 4L AND 4R. KNOWING MY POS FROM FLYING IN THE AREA LOT, I KEPT PARTICULAR ATTN OUTSIDE THE COCKPIT FOR TFC AND SPOTTED THIS PARTICULAR ACFT BEFORE THE CTLR EVEN CALLED IT OUT TO ME. I RESPONDED WITH A TALLY-HO AND HAD A VISUAL ON HIM THE ENTIRE TIME. WHEN OUR PATHS CROSSED, MY BEST JUDGEMENT WOULD SAY 500 FT SEPARATION VERTICALLY, WHICH IS WHAT IT WAS SUPPOSED TO BE. THE ACR WAS AT 6000 FT MSL. OUR POS WAS 5 DME NE OF RBV VORTAC OFF THE 035 DEG RADIAL. AFTER WE PASSED EACH OTHER, A PLT OF ACR FLT SAID 'THAT SMA WE JUST PASSED WAS NOT AT 6500 FT AND I'M RPTING A NEAR MISS. CAN I HAVE HIS TAIL NUMBER?' THE CTLR RESPONDED WITH 'WHAT IS THE REQUEST FOR?' THE PLT SAID 'MY TCASII IS INDICATING A SEPARATION OF 200 FT AND I NEED TO FILE A RPT.' THE CTLR OBLIGED AND GAVE MY TAIL NUMBER. AT THIS TIME, I IMMEDIATELY SAID 'THAT IS A NEGATIVE! MY ALT IS 6500 FT AND THE ALTIMETER IS 30.73.' THE CTLR RESPONDED TO SAY I HAD DONE NOTHING WRONG AND MY MODE C WAS SHOWING 6500 FT. I CALLED HER ONCE I GOT ON THE GND AT DCA AND SPOKE TO THE SHIFT SUPVR. HE TOLD ME TOO WORRY AND IF I RECEIVED ANY CALLS TO REFER THEM TO MR X. THE WORKING CTLR WAS Y. THE REASON I AM SUBMITTING THIS RPT IS TO BRING UP A COUPLE OF ISSUES. ONE BEING THE ACTUAL ACCURACY OF TCASII, THE PLT'S RELIABILITY UPON THIS EQUIP INSTEAD OF HIS OWN EYES, ESPECIALLY IN THE EXCELLENT VISIBILITY WE HAD, HIS JUDGEMENT ON OUR ACTUAL SEPARATION, AND HIS ACCUSATION RIGHT ON THE RADIO! I HAVE ALMOST 550 HRS TOTAL TIME WITH MULTI-ENG PVT. I WOULD NEVER ACCUSE SO QUICKLY OVER THE FEDERAL AIR WAVES. HE IS SUPPOSED TO BE 'PROFESSIONAL' AND PROBABLY HAS AT LEAST 2500 HRS TOTAL TIME. I WOULD LIKE SOME FEEDBACK ON THE ISSUE OF TCASII, HOW MUCH THE PIC SHOULD RELY ON IT IN VMC WHEN HE SHOULD LOOKING OUTSIDE, INSTEAD OF PLAYING VIDEO GAMES ON A FIRST GENERATION PIECE OF EQUIP.

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.