Controller report of TCASII issuing wrong direction RA temporarily.

Attributes
ACN	280272
Time
Date	199408
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bna
State Reference	TN
Altitude	msl bound lower : 2200 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bna
Operator	common carrier : air carrier
Make Model Name	SF 340B
Operating Under FAR Part	Part 135
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Make Model Name	PA-38 Tomahawk
Operating Under FAR Part	Part 91
Flight Phase	climbout : intermediate altitude
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	280272
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 0 vertical : 700
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

The SF34 was TCASII equipped and on an IFR flight plan inbound to bna. I received the handoff from arrival and turned the aircraft and descended him to 3000 ft. I observed a target squawking 1200 with a mode C readout of 2200 in front of the SF34. I called traffic. The mode C went to 2300 so I issued the traffic as climbing. The SF34 advised he had an RA to descend. The traffic was at 12 O'clock and 2 mi. I advised he should not descend but climb. He said that the RA had changed and now said climb. A descent would have caused the radar targets to merge at less than 500 ft indicated separation. If the pilot would have taken the descent RA and configured for a quick descent I feel the aircraft could have hit. The VFR aircraft called another radar sector and was idented as a PA38 and the mode C was verified. He was outside the class C airspace but was on and near the final for runway 20R at 2200-2300 ft in the middle of an arrival push.

Original NASA ASRS Text

Title: CTLR RPT OF TCASII ISSUING WRONG DIRECTION RA TEMPORARILY.

Narrative: THE SF34 WAS TCASII EQUIPPED AND ON AN IFR FLT PLAN INBOUND TO BNA. I RECEIVED THE HDOF FROM ARR AND TURNED THE ACFT AND DSNDED HIM TO 3000 FT. I OBSERVED A TARGET SQUAWKING 1200 WITH A MODE C READOUT OF 2200 IN FRONT OF THE SF34. I CALLED TFC. THE MODE C WENT TO 2300 SO I ISSUED THE TFC AS CLBING. THE SF34 ADVISED HE HAD AN RA TO DSND. THE TFC WAS AT 12 O'CLOCK AND 2 MI. I ADVISED HE SHOULD NOT DSND BUT CLB. HE SAID THAT THE RA HAD CHANGED AND NOW SAID CLB. A DSCNT WOULD HAVE CAUSED THE RADAR TARGETS TO MERGE AT LESS THAN 500 FT INDICATED SEPARATION. IF THE PLT WOULD HAVE TAKEN THE DSCNT RA AND CONFIGURED FOR A QUICK DSCNT I FEEL THE ACFT COULD HAVE HIT. THE VFR ACFT CALLED ANOTHER RADAR SECTOR AND WAS IDENTED AS A PA38 AND THE MODE C WAS VERIFIED. HE WAS OUTSIDE THE CLASS C AIRSPACE BUT WAS ON AND NEAR THE FINAL FOR RWY 20R AT 2200-2300 FT IN THE MIDDLE OF AN ARR PUSH.

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.