Narrative:

I was the relief first officer on flight to ZZZZ. At approximately XA00Z; the purser awakened me during my rest break to talk to the cockpit about a problem. Captain informed me that we had completely lost our standby attitude indicator. They had worked with maintenance control to try and get it back to no avail. He asked for my input on the wisdom of continuing to ZZZZ. I stated that operation over the entire continent of south america; on a moonless night; with numerous thunderstorms in the area; seemed a risky and unsafe operation. He said that he and first officer had come to the same conclusion. Despite being told that the MEL offers relief and that a standby ADI may be deferred; that must be considered in light of the fact that far 121.305 clearly states it must work to operate the aircraft. Any MEL relief must be considered under that highly restrictive light. Our location was about 250 mi from ZZZ and about 600 mi from ZZZ1. Neither location had a replacement gyro. WX in ZZZ1 was clear; and when down to a normal landing weight; we elected to divert to ZZZ1 where we would touch down just below 320000 pounds (maximum structural landing weight). Dispatch encouraged us to plan a quick turn to ZZZZ. We clearly stated we would be out of duty time unless the aircraft could be fixed and turned in 25 mins. They also tried to convince us to go to ZZZ2 direct. We felt that was unwise; as ZZZ1 offered the earliest legal weight VFR landing; and flying longer than that with a known problem exposed the aircraft to further risk if our main power systems went down. Additionally; ZZZ2 had overcast conditions and icing. We landed in ZZZ1 at 317000 pounds at approximately XA39Z; and parked at about XB50Z. We had calculated that we would need to be airborne by XC23 to be legal. As expected; it was obvious that repairs; paperwork; and pushback would take much more than 30 mins; so we declined the request by the company to take incentive pay; waive our duty day limits past 15 hours 30 mins; and to go to ZZZ2. We would've had a 17+ hour duty day; all on the backside of the clock; not safe; especially since neither captain nor first officer had any rest break at all; nor could one even start before early morning body clock time; the other several hours later. We felt it would be ok to proceed to ZZZ2 after repair; with our normal duty period; to get the jet in a position to be more efficiently re-crewed; and receive customer support for our passenger. We departed ZZZ1 at approximately XD12Z. Shortly after we reached cruise; the standby attitude indicator showed a slight nose-up bank attitude. We caged it; and it seemed to work fine for the next hour. Upon descent into ZZZ2; it clearly was not working any longer by FL180. We entered the malfunction in the aircraft maintenance log and decided the best course of action was to continue to ZZZ2 and land. We landed uneventfully at XF20Z.

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Original NASA ASRS Text

Title: B767 FLIGHT CREW REPORTS STAND-BY ATTITUDE INDICATOR FAILURE OVER THE ATLANTIC ENROUTE TO SOUTH AMERICA AND ELECTS TO DIVERT TO NEAREST SUITABLE AIRPORT.

Narrative: I WAS THE RELIEF FO ON FLT TO ZZZZ. AT APPROX XA00Z; THE PURSER AWAKENED ME DURING MY REST BREAK TO TALK TO THE COCKPIT ABOUT A PROB. CAPT INFORMED ME THAT WE HAD COMPLETELY LOST OUR STANDBY ATTITUDE INDICATOR. THEY HAD WORKED WITH MAINT CTL TO TRY AND GET IT BACK TO NO AVAIL. HE ASKED FOR MY INPUT ON THE WISDOM OF CONTINUING TO ZZZZ. I STATED THAT OP OVER THE ENTIRE CONTINENT OF SOUTH AMERICA; ON A MOONLESS NIGHT; WITH NUMEROUS TSTMS IN THE AREA; SEEMED A RISKY AND UNSAFE OP. HE SAID THAT HE AND FO HAD COME TO THE SAME CONCLUSION. DESPITE BEING TOLD THAT THE MEL OFFERS RELIEF AND THAT A STANDBY ADI MAY BE DEFERRED; THAT MUST BE CONSIDERED IN LIGHT OF THE FACT THAT FAR 121.305 CLEARLY STATES IT MUST WORK TO OPERATE THE ACFT. ANY MEL RELIEF MUST BE CONSIDERED UNDER THAT HIGHLY RESTRICTIVE LIGHT. OUR LOCATION WAS ABOUT 250 MI FROM ZZZ AND ABOUT 600 MI FROM ZZZ1. NEITHER LOCATION HAD A REPLACEMENT GYRO. WX IN ZZZ1 WAS CLEAR; AND WHEN DOWN TO A NORMAL LNDG WT; WE ELECTED TO DIVERT TO ZZZ1 WHERE WE WOULD TOUCH DOWN JUST BELOW 320000 LBS (MAX STRUCTURAL LNDG WT). DISPATCH ENCOURAGED US TO PLAN A QUICK TURN TO ZZZZ. WE CLEARLY STATED WE WOULD BE OUT OF DUTY TIME UNLESS THE ACFT COULD BE FIXED AND TURNED IN 25 MINS. THEY ALSO TRIED TO CONVINCE US TO GO TO ZZZ2 DIRECT. WE FELT THAT WAS UNWISE; AS ZZZ1 OFFERED THE EARLIEST LEGAL WT VFR LNDG; AND FLYING LONGER THAN THAT WITH A KNOWN PROB EXPOSED THE ACFT TO FURTHER RISK IF OUR MAIN PWR SYSTEMS WENT DOWN. ADDITIONALLY; ZZZ2 HAD OVCST CONDITIONS AND ICING. WE LANDED IN ZZZ1 AT 317000 LBS AT APPROX XA39Z; AND PARKED AT ABOUT XB50Z. WE HAD CALCULATED THAT WE WOULD NEED TO BE AIRBORNE BY XC23 TO BE LEGAL. AS EXPECTED; IT WAS OBVIOUS THAT REPAIRS; PAPERWORK; AND PUSHBACK WOULD TAKE MUCH MORE THAN 30 MINS; SO WE DECLINED THE REQUEST BY THE COMPANY TO TAKE INCENTIVE PAY; WAIVE OUR DUTY DAY LIMITS PAST 15 HRS 30 MINS; AND TO GO TO ZZZ2. WE WOULD'VE HAD A 17+ HR DUTY DAY; ALL ON THE BACKSIDE OF THE CLOCK; NOT SAFE; ESPECIALLY SINCE NEITHER CAPT NOR FO HAD ANY REST BREAK AT ALL; NOR COULD ONE EVEN START BEFORE EARLY MORNING BODY CLOCK TIME; THE OTHER SEVERAL HRS LATER. WE FELT IT WOULD BE OK TO PROCEED TO ZZZ2 AFTER REPAIR; WITH OUR NORMAL DUTY PERIOD; TO GET THE JET IN A POSITION TO BE MORE EFFICIENTLY RE-CREWED; AND RECEIVE CUSTOMER SUPPORT FOR OUR PAX. WE DEPARTED ZZZ1 AT APPROX XD12Z. SHORTLY AFTER WE REACHED CRUISE; THE STANDBY ATTITUDE INDICATOR SHOWED A SLIGHT NOSE-UP BANK ATTITUDE. WE CAGED IT; AND IT SEEMED TO WORK FINE FOR THE NEXT HR. UPON DSCNT INTO ZZZ2; IT CLEARLY WAS NOT WORKING ANY LONGER BY FL180. WE ENTERED THE MALFUNCTION IN THE ACFT MAINT LOG AND DECIDED THE BEST COURSE OF ACTION WAS TO CONTINUE TO ZZZ2 AND LAND. WE LANDED UNEVENTFULLY AT XF20Z.

Data retrieved from NASA's ASRS site as of May 2009 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.