Apparenty false TCAS warning leads to track deviation.

Attributes
ACN	178322
Time
Date	199105
Day	Tue
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 7000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sea
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 200 flight time total : 8000 flight time type : 3000
ASRS Report	178322
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 3500 flight time type : 2000
Events
Anomaly	non adherence : published procedure non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	Pilot Deviation

Narrative:

During the malay 1 arrival, approximately 15 mi southwest of sea, we got a traffic call from ATC: '11 O'clock, 3 mi, climbing.' then got a TCAS warning: 'traffic.' then about 3 seconds later: 'monitor vertical speed,' shortly followed by, 'climb, climb,' shortly followed by, 'clear of conflict.' during this time we flew past fourt intersection by about 4 mi before ATC told us to turn left to 320 degrees. ATC made a good traffic call. We saw the traffic well clear. The TCAS warning appeared to be in error and the warnings caused confusion on the approach. Supplemental information from acn 178327: we saw the air carrier medium large transport Y visually and on TCAS scope. Due to the position of the target, the TCAS appeared to be in error and the warnings issued for traffic we clearly saw as no factor visually and on the scope (TCAS) only served to pull our attention from making the required turn at fourt intersection.

Original NASA ASRS Text

Title: APPARENTY FALSE TCAS WARNING LEADS TO TRACK DEVIATION.

Narrative: DURING THE MALAY 1 ARR, APPROX 15 MI SW OF SEA, WE GOT A TFC CALL FROM ATC: '11 O'CLOCK, 3 MI, CLBING.' THEN GOT A TCAS WARNING: 'TFC.' THEN ABOUT 3 SECS LATER: 'MONITOR VERT SPD,' SHORTLY FOLLOWED BY, 'CLB, CLB,' SHORTLY FOLLOWED BY, 'CLR OF CONFLICT.' DURING THIS TIME WE FLEW PAST FOURT INTXN BY ABOUT 4 MI BEFORE ATC TOLD US TO TURN LEFT TO 320 DEGS. ATC MADE A GOOD TFC CALL. WE SAW THE TFC WELL CLR. THE TCAS WARNING APPEARED TO BE IN ERROR AND THE WARNINGS CAUSED CONFUSION ON THE APCH. SUPPLEMENTAL INFO FROM ACN 178327: WE SAW THE ACR MLG Y VISUALLY AND ON TCAS SCOPE. DUE TO THE POS OF THE TARGET, THE TCAS APPEARED TO BE IN ERROR AND THE WARNINGS ISSUED FOR TFC WE CLEARLY SAW AS NO FACTOR VISUALLY AND ON THE SCOPE (TCAS) ONLY SERVED TO PULL OUR ATTN FROM MAKING THE REQUIRED TURN AT FOURT INTXN.

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.