WHILE ACCOMPLISHING A TEST CARD ON A B777 ACFT; AN AVIONICS TECHNICIAN DISCOVERS AN INTERNAL FAULT IN THE ADIRU COMPUTER WITH A MAINT MESSAGE THAT ADIRU WOULD NOT ALLOW THE RAM AIR TURBINE (RAT) TO AUTOMATICALLY DEPLOY.

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WHILE ACCOMPLISHING CARD FOR ACFT X APRIL 2008; IT WAS DISCOVERED THAT AN INTERNAL FAULT IN THE ACFT ADIRU COMPUTER WOULD NOT ALLOW THE RAM AIR TURBINE (RAT) TO AUTOMATICALLY DEPLOY. THIS INTERNAL FAULT HAS BEEN OCCURRING IN THE ADIRU. IT WAS FIRST DETECTED IN JANUARY 2008. THIS WAS DETERMINED BY MY MAINT HISTORY. THE ADIRU WAS REPLACED TODAY TO SOLVE THE MAINT MESSAGE AND TO ALLOW THE CARD TO BE COMPLETED. THE QUESTION IS WHAT INTERNAL FAULTS WITH THIS UNIT WILL PREVENT THE DEPLOYMENT OF THE RAT. IN WORK CARD; IT ASKS TO INTERROGATE THE MAINT ACCESS TERMINAL TO DETERMINE IF FAULTS EXIST. IF SO; THE DECISION TO REPLACE THE UNIT IS IF IT CAUSES A FLT DECK EFFECT OR IF THE UNIT IS UNDER WARRANTY. ALSO TO CONTACT FLEET ENGINEERING. THERE HAS BEEN NO GUIDANCE ON WHAT WILL CAUSE WHAT WITH THIS UNIT. THIS INTERNAL FAULT SO FAR IS THE ONLY ONE THAT PREVENTS THE AUTOMATIC DEPLOYMENT OF THE RAT. THERE NEEDS TO BE A POLICY TO HAVE THIS UNIT REPAIRED IF THE FAULT OCCURS. THE MONITORING OF THE FAULT HAS BEEN GOING ON WITH NO FIX OR INFO ON WHAT WILL HAPPEN IF THIS IS NOT ACCOUNTED FOR. IT SHOULD NOT HAVE TO BE ACCOMPLISHED WHEN A CARD IS DUE; 6000 HRS. WORK CARD. NOT ENOUGH INFO OR ACCESS TO INFO TO DETERMINE IF FAULT CAN CONTRIBUTE TO SAFETY OF FLT ITEMS. SUCH AS AUTOMATIC DEPLOYMENT OF RAT.