<< >> NASA ASRS Report 964458, August 2011

A B757 received a TCAS RA at FL215 descending and climbed as commanded but the captain decided at FL230 it was a false alert and continued the descent. Most likely this was a null bus fault.

Attributes
ACN	964458
Time
Date	201108
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Light	Night
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	TCAS Equipment
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 16000 Flight Crew Type 2000
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

Descending to 11;000 ft; at FL215 got TCAS conflict with climb solution. Disconnected autopilot and attempted escape maneuver. Could not silence conflict. The conflicting aircraft was shown at 12 o'clock and always at our altitude during climb. Decided at FL230 that it was a false image and returned to descent. This aircraft had a two day history of uncontrolled water leak with forward galley and lav. No further false warnings during descent.

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Original NASA ASRS Text

Title: A B757 received a TCAS RA at FL215 descending and climbed as commanded but the Captain decided at FL230 it was a false alert and continued the descent. Most likely this was a Null Bus fault.

Narrative: Descending to 11;000 FT; at FL215 got TCAS conflict with climb solution. Disconnected autopilot and attempted escape maneuver. Could not silence conflict. The conflicting aircraft was shown at 12 o'clock and always at our altitude during climb. Decided at FL230 that it was a false image and returned to descent. This aircraft had a two day history of uncontrolled water leak with forward galley and Lav. No further false warnings during descent.

Data retrieved from NASA's ASRS site as of April 2012 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.