A B777 crew responded to a TCAS RA from traffic at 12 o'clock 200 ft low while on approach to sbgr b...

Narrative:

Working sbgr approach control during vectors for ILS 9R with descent clearance to 5;500 ft and passing approximately 6;500 ft a 'climb now' RA was received. The RA target indicated 200 ft below at 12 to 1 o'clock. The autopilot was disconnected and climb was initiated. ATC was advised that we were climbing and responding to an RA. ATC was very busy with much frequency congestion and did not acknowledge our transmission. Shortly after initiating the climb all TCAS information stopped. There was never any vertical speed guidance during the event other than a momentary indication on pfd and a clear of conflict message was never given. We were in visual conditions during the event and there was no visual contact with any aircraft traffic nor did we receive a TCAS TA advisory prior to the RA. After all TCAS warnings stopped a slow descent back to our original cleared altitude was started and we requested further descent from ATC and continued the approach to landing. Given the conflicting indications that we had I feel this RA was possibly a TCAS anomaly possibly from another aircraft transponder transmitting erroneous information.

Original NASA ASRS Text

Title: A B777 Crew responded to a TCAS RA from traffic at 12 o'clock 200 FT low while on approach to SBGR but the warning was apparently false and may have been a null bus fault.

Narrative: Working SBGR Approach Control during vectors for ILS 9R with descent clearance to 5;500 FT and passing approximately 6;500 FT a 'climb now' RA was received. The RA target indicated 200 FT below at 12 to 1 o'clock. The autopilot was disconnected and climb was initiated. ATC was advised that we were climbing and responding to an RA. ATC was very busy with much frequency congestion and did not acknowledge our transmission. Shortly after initiating the climb all TCAS information stopped. There was never any vertical speed guidance during the event other than a momentary indication on PFD and a clear of conflict message was never given. We were in visual conditions during the event and there was no visual contact with any aircraft traffic nor did we receive a TCAS TA advisory prior to the RA. After all TCAS warnings stopped a slow descent back to our original cleared altitude was started and we requested further descent from ATC and continued the approach to landing. Given the conflicting indications that we had I feel this RA was possibly a TCAS anomaly possibly from another aircraft transponder transmitting erroneous information.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	989525
Time
Date	201201
Local Time Of Day	0601-1200
Place
Locale Reference	SBGR.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	TCAS Equipment
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 19910
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude

A B777 crew responded to a TCAS RA from traffic at 12 o'clock 200 ft low while on approach to sbgr but the warning was apparently false and may have been a null bus fault.