An air carrier large transport climbed in response to a TCASII command.

Attributes
ACN	255593
Time
Date	199310
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ipl
State Reference	CA
Altitude	agl bound lower : 18500 agl bound upper : 18500
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 12000 flight time type : 9500
ASRS Report	255593
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 800
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

Descending into san, passing 18500 ft to 10000 ft, we received a TCASII RA saying 'climb.' a climb was initiated and about 30 seconds later an aircraft passed under us. He was in our 12 O'clock position and came directly at us. ZLA said he was never on their radar. The center also told us that they have had numerous instances of pop-up traffic in this area. Perhaps this could be investigated to avoid future recurrences.

Original NASA ASRS Text

Title: AN ACR LGT CLBED IN RESPONSE TO A TCASII COMMAND.

Narrative: DSNDING INTO SAN, PASSING 18500 FT TO 10000 FT, WE RECEIVED A TCASII RA SAYING 'CLB.' A CLB WAS INITIATED AND ABOUT 30 SECONDS LATER AN ACFT PASSED UNDER US. HE WAS IN OUR 12 O'CLOCK POS AND CAME DIRECTLY AT US. ZLA SAID HE WAS NEVER ON THEIR RADAR. THE CTR ALSO TOLD US THAT THEY HAVE HAD NUMEROUS INSTANCES OF POP-UP TFC IN THIS AREA. PERHAPS THIS COULD BE INVESTIGATED TO AVOID FUTURE RECURRENCES.

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.