Air carrier X TCASII RA had less than standard separation from small aircraft Y. System error.

Attributes
ACN	223647
Time
Date	199210
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lax
State Reference	CA
Altitude	msl bound lower : 1500 msl bound upper : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : lax
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Aircraft
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 8000 flight time type : 3000
ASRS Report	233647
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 2000 flight time type : 1500
ASRS Report	223646
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation non adherence : far other anomaly other other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 1000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X inside limma on a coupled ILS approach to 25L (autoland) at lax. At about 1500 ft MSL, when we received a TCASII 'traffic, traffic' alert followed by an RA of 'descend,' then 'do not climb.' the traffic was a low wing single engine aircraft Y traveling from south to north (left to right) at about 1200 to 1300 ft MSL. Tower also advised us of the traffic a little later. I saw the other aircraft ahead of us and to the left during the TCASII alert stage, and I could determine that it would go from south of the localizer to north of the localizer by the time we passed abeam. When we did pass abeam, the other traffic was north of us at about the same altitude. I would say the closest we came to each other was more than 500 ft and less than 1000 ft. We remained coupled to both autoplts and made an uneventful autoland on 25L at lax.

Original NASA ASRS Text

Title: ACR X TCASII RA HAD LTSS FROM SMA Y. SYS ERROR.

Narrative: ACR X INSIDE LIMMA ON A COUPLED ILS APCH TO 25L (AUTOLAND) AT LAX. AT ABOUT 1500 FT MSL, WHEN WE RECEIVED A TCASII 'TFC, TFC' ALERT FOLLOWED BY AN RA OF 'DSND,' THEN 'DO NOT CLB.' THE TFC WAS A LOW WING SINGLE ENG ACFT Y TRAVELING FROM S TO N (L TO R) AT ABOUT 1200 TO 1300 FT MSL. TWR ALSO ADVISED US OF THE TFC A LITTLE LATER. I SAW THE OTHER ACFT AHEAD OF US AND TO THE L DURING THE TCASII ALERT STAGE, AND I COULD DETERMINE THAT IT WOULD GO FROM S OF THE LOC TO N OF THE LOC BY THE TIME WE PASSED ABEAM. WHEN WE DID PASS ABEAM, THE OTHER TFC WAS N OF US AT ABOUT THE SAME ALT. I WOULD SAY THE CLOSEST WE CAME TO EACH OTHER WAS MORE THAN 500 FT AND LESS THAN 1000 FT. WE REMAINED COUPLED TO BOTH AUTOPLTS AND MADE AN UNEVENTFUL AUTOLAND ON 25L AT LAX.

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.