Air carrier left assigned altitude due to TCAS ii alert.

Attributes
ACN	173751
Time
Date	199103
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : cae
State Reference	SC
Altitude	msl bound lower : 28000 msl bound upper : 29500
Environment
Light	Night
Aircraft 1
Controlling Facilities	artcc : zjx tower : luk
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 6
ASRS Report	173751
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	other
Consequence	faa : reviewed incident with flight crew
Supplementary
Air Traffic Incident	Pilot Deviation other

Narrative:

Air carrier X was nebnd at FL290. Air carrier Y was climbing southbound to FL280. X was advised of the traffic. As the targets got close (approximately 2 mi) air carrier X advised me that he had a TCAS ii alert and was climbing. X climbed approximately 500'. As things worked out there was no harm. It was pure luck that there was not an aircraft above air carrier X. The aircraft were separated, and a safe situation was turned into a possible dangerous one. In a brief discussion with the pilots immediately after the situation the air carrier Y pilot advised that he also had a TCAS ii alert. The air carrier X pilot expressed his unhappiness with the system as did I. The use of TCAS ii in positive control area (positive control airspace) is unnecessary and potentially dangerous. If there had been traffic at FL310 above air carrier X I feel that the TCAS ii alert would have still told him to climb and an operational error would have occurred.

Original NASA ASRS Text

Title: ACR LEFT ASSIGNED ALT DUE TO TCAS II ALERT.

Narrative: ACR X WAS NEBND AT FL290. ACR Y WAS CLBING SBND TO FL280. X WAS ADVISED OF THE TFC. AS THE TARGETS GOT CLOSE (APPROX 2 MI) ACR X ADVISED ME THAT HE HAD A TCAS II ALERT AND WAS CLBING. X CLBED APPROX 500'. AS THINGS WORKED OUT THERE WAS NO HARM. IT WAS PURE LUCK THAT THERE WAS NOT AN ACFT ABOVE ACR X. THE ACFT WERE SEPARATED, AND A SAFE SITUATION WAS TURNED INTO A POSSIBLE DANGEROUS ONE. IN A BRIEF DISCUSSION WITH THE PLTS IMMEDIATELY AFTER THE SITUATION THE ACR Y PLT ADVISED THAT HE ALSO HAD A TCAS II ALERT. THE ACR X PLT EXPRESSED HIS UNHAPPINESS WITH THE SYS AS DID I. THE USE OF TCAS II IN PCA (POSITIVE CTL AIRSPACE) IS UNNECESSARY AND POTENTIALLY DANGEROUS. IF THERE HAD BEEN TFC AT FL310 ABOVE ACR X I FEEL THAT THE TCAS II ALERT WOULD HAVE STILL TOLD HIM TO CLB AND AN OPERATIONAL ERROR WOULD HAVE OCCURRED.

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.