Medium large transport on approach gets TCASII RA from commuter supposedly on parallel runway.

Attributes
ACN	291434
Time
Date	199412
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lax
State Reference	CA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	291434
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : instrument
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : insufficient time
Consequence	Other
Miss Distance	horizontal : 200 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

We were cleared for ILS 25R and were told a commuter aircraft would follow us for runway 25L. I believe we were inside the marker and received a TCASII descend command. I finally saw the commuter aircraft and would guess the airplane was approximately 200 ft above and behind us. I guess that the commuter aircraft closed on us, causing TCASII to activate. Commuter pilot should have stayed on ILS and maintained a safe distance from our aircraft.

Original NASA ASRS Text

Title: MLG ON APCH GETS TCASII RA FROM COMMUTER SUPPOSEDLY ON PARALLEL RWY.

Narrative: WE WERE CLRED FOR ILS 25R AND WERE TOLD A COMMUTER ACFT WOULD FOLLOW US FOR RWY 25L. I BELIEVE WE WERE INSIDE THE MARKER AND RECEIVED A TCASII DSND COMMAND. I FINALLY SAW THE COMMUTER ACFT AND WOULD GUESS THE AIRPLANE WAS APPROX 200 FT ABOVE AND BEHIND US. I GUESS THAT THE COMMUTER ACFT CLOSED ON US, CAUSING TCASII TO ACTIVATE. COMMUTER PLT SHOULD HAVE STAYED ON ILS AND MAINTAINED A SAFE DISTANCE FROM OUR ACFT.

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.