A TCASII RA leads an medium large transport toward a collision rather than away from it.

Attributes
ACN	240214
Time
Date	199304
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : smo airport : lax
State Reference	CA
Altitude	msl bound lower : 9300 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 5100 flight time type : 1200
ASRS Report	240214
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot conflict : airborne less severe non adherence : required legal separation non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 1500 vertical : 500
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

Cleared to descend to 10000 ft MSL. At about 11000 ft MSL, TCASII RA occurred with 'increase descent' command to 1500- 2000 ft down vertical speed. Approach called out traffic climbing to 9000 ft. TCASII commanded 'increase descent' to 2500 ft plus vertical speed down and 'crossing descent.' as PF (on autoplt), I followed the TCASII commands, descended through 10000 ft in response to the TCASII RA. Visually sighted the traffic an air carrier B medium large transport at 2 O'clock and approximately 500 ft low. TCASII RA was still commanding a descent through air carrier B altitude. Disconnected the autoplt and stopped the descent at about 9300 ft MSL and air carrier B passed under us. If we had continued to follow TCASII RA we would have hit air carrier B. Returned to 10000 ft MSL, the altitude we were cleared to. Note: the TCASII commands were so loud they interfered with hearing lax approach and also with pilot-to-pilot communication.

Original NASA ASRS Text

Title: A TCASII RA LEADS AN MLG TOWARD A COLLISION RATHER THAN AWAY FROM IT.

Narrative: CLRED TO DSND TO 10000 FT MSL. AT ABOUT 11000 FT MSL, TCASII RA OCCURRED WITH 'INCREASE DSCNT' COMMAND TO 1500- 2000 FT DOWN VERT SPD. APCH CALLED OUT TFC CLBING TO 9000 FT. TCASII COMMANDED 'INCREASE DSCNT' TO 2500 FT PLUS VERT SPD DOWN AND 'XING DSCNT.' AS PF (ON AUTOPLT), I FOLLOWED THE TCASII COMMANDS, DSNDED THROUGH 10000 FT IN RESPONSE TO THE TCASII RA. VISUALLY SIGHTED THE TFC AN ACR B MLG AT 2 O'CLOCK AND APPROX 500 FT LOW. TCASII RA WAS STILL COMMANDING A DSCNT THROUGH ACR B ALT. DISCONNECTED THE AUTOPLT AND STOPPED THE DSCNT AT ABOUT 9300 FT MSL AND ACR B PASSED UNDER US. IF WE HAD CONTINUED TO FOLLOW TCASII RA WE WOULD HAVE HIT ACR B. RETURNED TO 10000 FT MSL, THE ALT WE WERE CLRED TO. NOTE: THE TCASII COMMANDS WERE SO LOUD THEY INTERFERED WITH HEARING LAX APCH AND ALSO WITH PLT-TO-PLT COM.

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.