Narrative:

After takeoff; we received a tat probe EICAS indication along with failure of the autothrottles; LNAV; VNAV; thrust reference indications; and wind readout. We had seen this exact item written up twice in the last day in the logbook. I remained the pilot flying and talked with ATC while the captain got out the QRH procedure as we had briefed. The captain also looked up in the MEL what the restrictions may be for this problem and found that the aircraft could not be dispatched into known or forecast icing. We both agreed that we would likely encounter icing conditions throughout this flight and decided it best to return to our departure airport. While the captain notified the company and spoke with our maintenance; I worked with ATC to avoid weather on our departure. The company agreed that we should return and as we advised ATC of our intentions; we encountered icing conditions and subsequently were required to turn on our engine anti-ice due to temperatures below 10 degrees. At this point; we could not be completely sure of the reliability of our instruments and discussed the need to pay particularly close attention as we descended back toward our departure airport in IMC conditions. We decided to declare an emergency at this point; which afforded us the time needed to prepare for and brief the approach. This also allowed us relief on the crossing restrictions on the arrival since we still had some altitude to lose and needed more time to prepare for landing. While I flew and coordinated with approach; the captain briefed the flight attendants and passengers and then joined me in setting up for an approach to the longest runway. We landed uneventfully 30;000 pounds below maximum landing weight. The captain put the discrepancy into the logbook for the third time in the last few days.

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Original NASA ASRS Text

Title: A B767-300 EICAS alerted TAT PROBE failure with the loss of VNAV; LNAV; Autothrottles and wind read out. Because icing was expected; an emergency was declared and the flight returned to the departure airport.

Narrative: After takeoff; we received a TAT PROBE EICAS indication along with failure of the Autothrottles; LNAV; VNAV; Thrust Reference Indications; and wind readout. We had seen this exact item written up twice in the last day in the logbook. I remained the pilot flying and talked with ATC while the Captain got out the QRH procedure as we had briefed. The Captain also looked up in the MEL what the restrictions may be for this problem and found that the aircraft could not be dispatched into known or forecast icing. We both agreed that we would likely encounter icing conditions throughout this flight and decided it best to return to our departure airport. While the Captain notified the company and spoke with our maintenance; I worked with ATC to avoid weather on our departure. The Company agreed that we should return and as we advised ATC of our intentions; we encountered icing conditions and subsequently were required to turn on our engine anti-ice due to temperatures below 10 degrees. At this point; we could not be completely sure of the reliability of our instruments and discussed the need to pay particularly close attention as we descended back toward our departure airport in IMC conditions. We decided to declare an emergency at this point; which afforded us the time needed to prepare for and brief the approach. This also allowed us relief on the crossing restrictions on the arrival since we still had some altitude to lose and needed more time to prepare for landing. While I flew and coordinated with Approach; the Captain briefed the Flight Attendants and passengers and then joined me in setting up for an approach to the longest runway. We landed uneventfully 30;000 LBS below maximum landing weight. The Captain put the discrepancy into the logbook for the third time in the last few days.

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.