Narrative:

Mid dec/xa/03, the B777 fleet began experiencing long delays and 'standby one' scratch pad messages whenever a dfw arrival, approach, or runway was selected. The delays locked up the CDU from any input for 30 seconds to 1 min. There have been multiple crews on many different B777's seeing this problem with the FMC. Sometimes it has been written up and sometimes only verbally told to the mechanic or incoming crew. I filled out a captain's report 10 days ago and have not had a response. I have flown with several check airmen who agree that this is a significant problem and safety issue, and have said they will talk to the fleet manager and flight operations team. Nothing has happened. The original problem started 2 yrs ago when the dfw approachs were linked to the arrs and the downwind leg was added for FMC aircraft. Last spring, the flight operations team technician pilot said that the problem was caused by trying to use a common navigation database for both the B777 and B767/757 fleet. That the B777 would be slow to accept the B767/757 database, but until all the B767/757 were pegasus fmcs, company would not go to using the B777 database. This problem is along the same lines, but makes the FMC unusable for up to a min while flying, preventing crews from complying with ATC directives. This is a safety issue. On the new database that was effective dec/thu/03, the downwind legs were changed and new waypoints were added. I believe this might be the reason the FMC now locks up when the dfw arrs/approachs are selected. This problem can be duplicated both in the air and on the ground. Line maintenance has been tracking this problem since dec/wed/03, but has not gotten a response from higher up. Callback conversation with reporter revealed the following information: the B777 and B757/767 fleets use the same navigation database. The B757/767 fleet is being modified to be compatible with and use the same database as the B777, however the modifications have been stopped due to economic concerns. The B757/767 fleet has not reported FMC problems apparently because the current database in use is written for that fleet. The last database revision issued has corrected the lockup problem that was being encountered, but the B777 FMC is still very slow when any changes are required, especially during the dfw arrs. A response to the reporter from the technical department indicated that the aircraft and FMC manufacturer, as well as the database supplier, are working on the problem. There is new software in the process of FAA certification but the reporter assumes that it will be withheld until the B757/767 fleet modification is complete. To date, the reporter is unaware of any major air traffic problems being caused, but contends that the potential is there.

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Original NASA ASRS Text

Title: DELAYED RESPONSE TIME AND LOCK UP OF THE FMC ON THE B777 CAUSES DELAYED RESPONSE TO ATC DIRECTIVES DURING APCHS TO THE DFW AREA. SOFTWARE PROBS AND THE USE OF A COMMON NAV DATABASE WITH THE B757-767 ARE THE SUSPECTED CAUSE.

Narrative: MID DEC/XA/03, THE B777 FLEET BEGAN EXPERIENCING LONG DELAYS AND 'STANDBY ONE' SCRATCH PAD MESSAGES WHENEVER A DFW ARR, APCH, OR RWY WAS SELECTED. THE DELAYS LOCKED UP THE CDU FROM ANY INPUT FOR 30 SECONDS TO 1 MIN. THERE HAVE BEEN MULTIPLE CREWS ON MANY DIFFERENT B777'S SEEING THIS PROB WITH THE FMC. SOMETIMES IT HAS BEEN WRITTEN UP AND SOMETIMES ONLY VERBALLY TOLD TO THE MECH OR INCOMING CREW. I FILLED OUT A CAPT'S RPT 10 DAYS AGO AND HAVE NOT HAD A RESPONSE. I HAVE FLOWN WITH SEVERAL CHK AIRMEN WHO AGREE THAT THIS IS A SIGNIFICANT PROB AND SAFETY ISSUE, AND HAVE SAID THEY WILL TALK TO THE FLEET MGR AND FLT OPS TEAM. NOTHING HAS HAPPENED. THE ORIGINAL PROB STARTED 2 YRS AGO WHEN THE DFW APCHS WERE LINKED TO THE ARRS AND THE DOWNWIND LEG WAS ADDED FOR FMC ACFT. LAST SPRING, THE FLT OPS TEAM TECHNICIAN PLT SAID THAT THE PROB WAS CAUSED BY TRYING TO USE A COMMON NAV DATABASE FOR BOTH THE B777 AND B767/757 FLEET. THAT THE B777 WOULD BE SLOW TO ACCEPT THE B767/757 DATABASE, BUT UNTIL ALL THE B767/757 WERE PEGASUS FMCS, COMPANY WOULD NOT GO TO USING THE B777 DATABASE. THIS PROB IS ALONG THE SAME LINES, BUT MAKES THE FMC UNUSABLE FOR UP TO A MIN WHILE FLYING, PREVENTING CREWS FROM COMPLYING WITH ATC DIRECTIVES. THIS IS A SAFETY ISSUE. ON THE NEW DATABASE THAT WAS EFFECTIVE DEC/THU/03, THE DOWNWIND LEGS WERE CHANGED AND NEW WAYPOINTS WERE ADDED. I BELIEVE THIS MIGHT BE THE REASON THE FMC NOW LOCKS UP WHEN THE DFW ARRS/APCHS ARE SELECTED. THIS PROB CAN BE DUPLICATED BOTH IN THE AIR AND ON THE GND. LINE MAINT HAS BEEN TRACKING THIS PROB SINCE DEC/WED/03, BUT HAS NOT GOTTEN A RESPONSE FROM HIGHER UP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE B777 AND B757/767 FLEETS USE THE SAME NAV DATABASE. THE B757/767 FLEET IS BEING MODIFIED TO BE COMPATIBLE WITH AND USE THE SAME DATABASE AS THE B777, HOWEVER THE MODIFICATIONS HAVE BEEN STOPPED DUE TO ECONOMIC CONCERNS. THE B757/767 FLEET HAS NOT RPTED FMC PROBS APPARENTLY BECAUSE THE CURRENT DATABASE IN USE IS WRITTEN FOR THAT FLEET. THE LAST DATABASE REVISION ISSUED HAS CORRECTED THE LOCKUP PROB THAT WAS BEING ENCOUNTERED, BUT THE B777 FMC IS STILL VERY SLOW WHEN ANY CHANGES ARE REQUIRED, ESPECIALLY DURING THE DFW ARRS. A RESPONSE TO THE RPTR FROM THE TECHNICAL DEPT INDICATED THAT THE ACFT AND FMC MANUFACTURER, AS WELL AS THE DATABASE SUPPLIER, ARE WORKING ON THE PROB. THERE IS NEW SOFTWARE IN THE PROCESS OF FAA CERTIFICATION BUT THE RPTR ASSUMES THAT IT WILL BE WITHHELD UNTIL THE B757/767 FLEET MODIFICATION IS COMPLETE. TO DATE, THE RPTR IS UNAWARE OF ANY MAJOR AIR TFC PROBS BEING CAUSED, BUT CONTENDS THAT THE POTENTIAL IS THERE.

Data retrieved from NASA's ASRS site as of July 2007 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.