Narrative:

I was working local control at that moment working several inbound aircraft. A helicopter checked in on frequency 4 mi southeast of airport VFR. I observed his target on the BRITE scope as well as the target of cga X (on an IFR flight plan) inbound about 1 1/2 mi northeast of obk. The helicopter wanted to go nwbound from present position. I instructed him to fly east of the approach course of runway 16 due to cga X 1 1/2 northeast of obk being vectored inbound for the ILS runway 16 approach. Helicopter requested to overfly the airport and proceed nwbound to his destination. The jet (cga X) reported on frequency on a 2 mi final so I gave him his landing clearance. While this was all happening, the helicopter had overflown the airport and was west of the approach course of runway 16 headed nwbound at 1100 ft MSL. As the jet approached 1 mi final the pilot advised me that he was going around due to 'TCASII resolution.' I looked out the window and the BRITE scope and there was only 1 other target in his area, the helicopter about a mile west of his position going the opposite direction (nwbound) at 1100 ft MSL. I advised him that the helicopter was no factor. At the time that he was advising me that he was going around, the aircraft nosed up so I gave him instructions to go around and he landed after that. The tower supervisor talked to the copilot after that and we found out that the TCASII equipment on the plane was giving them a 'climb up' warning. Luckily, traffic workload was low. I think the accuracy of the TCASII equipment should be reviewed and pilots should not rely mainly on it. If possible, confirm with ATC before executing evasive maneuvers.

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Original NASA ASRS Text

Title: CGA GETS A TCASII ON SHORT FINAL AND STARTS TO CLB, THEN CHANGES HIS MIND AND LANDS. TFC WAS A COPTER LOW.

Narrative: I WAS WORKING LCL CTL AT THAT MOMENT WORKING SEVERAL INBOUND ACFT. A HELI CHKED IN ON FREQ 4 MI SE OF ARPT VFR. I OBSERVED HIS TARGET ON THE BRITE SCOPE AS WELL AS THE TARGET OF CGA X (ON AN IFR FLT PLAN) INBOUND ABOUT 1 1/2 MI NE OF OBK. THE HELI WANTED TO GO NWBOUND FROM PRESENT POS. I INSTRUCTED HIM TO FLY E OF THE APCH COURSE OF RWY 16 DUE TO CGA X 1 1/2 NE OF OBK BEING VECTORED INBOUND FOR THE ILS RWY 16 APCH. HELI REQUESTED TO OVERFLY THE ARPT AND PROCEED NWBOUND TO HIS DEST. THE JET (CGA X) RPTED ON FREQ ON A 2 MI FINAL SO I GAVE HIM HIS LNDG CLRNC. WHILE THIS WAS ALL HAPPENING, THE HELI HAD OVERFLOWN THE ARPT AND WAS W OF THE APCH COURSE OF RWY 16 HEADED NWBOUND AT 1100 FT MSL. AS THE JET APCHED 1 MI FINAL THE PLT ADVISED ME THAT HE WAS GOING AROUND DUE TO 'TCASII RESOLUTION.' I LOOKED OUT THE WINDOW AND THE BRITE SCOPE AND THERE WAS ONLY 1 OTHER TARGET IN HIS AREA, THE HELI ABOUT A MILE W OF HIS POS GOING THE OPPOSITE DIRECTION (NWBOUND) AT 1100 FT MSL. I ADVISED HIM THAT THE HELI WAS NO FACTOR. AT THE TIME THAT HE WAS ADVISING ME THAT HE WAS GOING AROUND, THE ACFT NOSED UP SO I GAVE HIM INSTRUCTIONS TO GAR AND HE LANDED AFTER THAT. THE TWR SUPVR TALKED TO THE COPLT AFTER THAT AND WE FOUND OUT THAT THE TCASII EQUIP ON THE PLANE WAS GIVING THEM A 'CLB UP' WARNING. LUCKILY, TFC WORKLOAD WAS LOW. I THINK THE ACCURACY OF THE TCASII EQUIP SHOULD BE REVIEWED AND PLTS SHOULD NOT RELY MAINLY ON IT. IF POSSIBLE, CONFIRM WITH ATC BEFORE EXECUTING EVASIVE MANEUVERS.

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.