Large transport level on step down descent receives TCASII RA to climb. Responds.

Attributes
ACN	210198
Time
Date	199205
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sna
State Reference	CA
Altitude	msl bound lower : 5000 msl bound upper : 5600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sna
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 8500 flight time type : 1500
ASRS Report	210198
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 170 flight time total : 18000 flight time type : 1700
ASRS Report	210109
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

During arrival at john wayne airport (sna) we were level at 5000 ft MSL when TCASII indicated traffic just to the left of our nose less than a mi, at 4900 ft MSL and commanded an RA to climb. A climb was initiated to approximately 5600 ft. ATC was advised of the evasive maneuver and our deviation from the assigned altitude, as commanded by TCASII. ATC then advised that no traffic was observed in the area and we returned to our assigned altitude. No visual contact with the traffic was observed. We can only assume that it was a false warning generated by TCASII.

Original NASA ASRS Text

Title: LGT LEVEL ON STEP DOWN DSCNT RECEIVES TCASII RA TO CLB. RESPONDS.

Narrative: DURING ARR AT JOHN WAYNE ARPT (SNA) WE WERE LEVEL AT 5000 FT MSL WHEN TCASII INDICATED TFC JUST TO THE L OF OUR NOSE LESS THAN A MI, AT 4900 FT MSL AND COMMANDED AN RA TO CLB. A CLB WAS INITIATED TO APPROX 5600 FT. ATC WAS ADVISED OF THE EVASIVE MANEUVER AND OUR DEV FROM THE ASSIGNED ALT, AS COMMANDED BY TCASII. ATC THEN ADVISED THAT NO TFC WAS OBSERVED IN THE AREA AND WE RETURNED TO OUR ASSIGNED ALT. NO VISUAL CONTACT WITH THE TFC WAS OBSERVED. WE CAN ONLY ASSUME THAT IT WAS A FALSE WARNING GENERATED BY TCASII.

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.