B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 115; Flight Crew Total 21200; Flight Crew Type 6500
Human-Machine Interface; Workload; Confusion; Distraction
Aircraft Equipment Problem Less Severe
Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented; General Maintenance Action
Aircraft
After departing we were being vectored when we got an RA. We responded by executing a 1G downward pitch as directed by the TCAS Prompt. We reported RA to ATC; who had no traffic within 10 miles. TCAS indicated anon transponder equipped target was +200 feet above us. I never saw the traffic in question. In addition; the TCAS alert was nonstandard as it called 'traffic; traffic' but commanded us down; indicated on the ADI. We climbed back toward the altitude assigned. We never got a clear of conflict message. The RA simply disappeared.After leveling in cruise; we got another RA with this time a 'descend; descend' prompt and ADI indications for another no transponder equipped aircraft. We could not see and aircraft and ATC had no target. RA continued for 3-5 minutes until it disappeared. We contacted maintenance; wrote up the A/C and deactivated TCAS.
Shortly after a B757 departed the TCAS began reporting an RA with no traffic in the area. The alert ceased and the crew climbed to cruise altitude where another phantom RA event alerted. A null bus fault was assumed.