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During descent a B777 TCAS generated an apparent false traffic target and issued a descend command followed by a climb command. ATC reported no traffic in the area so this is an assumed null bus fault.
| Attributes | |
| ACN | 1262975 |
| Time | |
| Date | 201505 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B777 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | TCAS Equipment |
| Person 1 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 190 Flight Crew Total 17300 Flight Crew Type 1100 |
| Person 2 | |
| Function | Pilot Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude |
Narrative:
On descent we were passing through FL210 when we got a TCAS RA. The TCAS showed a target at our precise location and at our exact altitude. The captain responded to the RA and descended. When we got to about FL203 we got another TCAS RA that told us to climb. The TCAS showed a target again at our exact location and altitude. The captain again responded to the RA. The RA and target disappeared after a climb of about 100-200 feet. We reported all of this to the center controller who said that he showed no aircraft in our vicinity. He said he would write it up on his end but that he recommended we check our equipment. It appeared to us that our TCAS was responding to our own aircraft as an intruder aircraft. The captain said that he had heard of this happening during the early days of TCAS use. After landing the captain wrote up the TCAS and called maintenance to explain the writeup.
Original NASA ASRS Text
Title: During descent a B777 TCAS generated an apparent false traffic target and issued a descend command followed by a climb command. ATC reported no traffic in the area so this is an assumed null bus fault.
Narrative: On descent we were passing through FL210 when we got a TCAS RA. The TCAS showed a target at our precise location and at our exact altitude. The Captain responded to the RA and descended. When we got to about FL203 we got another TCAS RA that told us to climb. The TCAS showed a target again at our exact location and altitude. The Captain again responded to the RA. The RA and target disappeared after a climb of about 100-200 feet. We reported all of this to the Center Controller who said that he showed no aircraft in our vicinity. He said he would write it up on his end but that he recommended we check our equipment. It appeared to us that our TCAS was responding to our own aircraft as an intruder aircraft. The Captain said that he had heard of this happening during the early days of TCAS use. After landing the Captain wrote up the TCAS and called Maintenance to explain the writeup.
Data retrieved from NASA's ASRS site 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.