Narrative:

On oct/xx/96, we were assigned to fly from anc to sfo. As an A320 line check airman, I occupied the right seat during this flight and performed PNF duties, while conducting IOE with captain who occupied the left seat and performed PF duties during this flight. We arrived at the aircraft at 30 mins prior to scheduled departure. The temperature at the time of departure was approximately 17 degree F. The aircraft had remained overnight for 13 hours and this would be the first flight of the day. Upon entering the cockpit, I turned all 3 of the IRS units from the off position to navigation and then conducted a preflight exterior inspection while IOE captain a conducted the cockpit setup. The IRS alignment was completed by captain a initializing the mcdu (multifunction control and display unit) page a. The present position was inserted as 'panc' and the correct latitude and longitude was verified as that shown on the commercial chart 10-9 page. During the preflight all 3 IRS's aligned normally and the map correctly indicated our position on the anchorage airport and in relationship to runway 32 which was the selected departure runway. The taxi out and takeoff from runway 32 was uneventful. 2 mins after takeoff the mcdu indicated 'check aircraft position.' a check of the right mcdu position monitor page indicated the following: FMC own: 6110.3N/14918.9W, FMC opp: 6110.3N/14919.3W, radio 6110.3N/14919.0W, IRS mix: 61103N/13404.7W, all 3 IRS deviations indicated 99.9 NM. A check of all 3 IRS units present position on the overhead adirs control display unit indicated that all 3 units were at 6110.3N/13404.7W which would put our position in the vicinity of the yxy VOR, some 440 mi east of our actual position. We advised ATC we were now a 'slash alpha' equipment suffix and we proceeded uneventfully via high altitude airways to sfo. While en route we contacted dispatch, and maintenance coordinator and attempted to contact the A320 fleet, to advise them of this anomaly. Maintenance coordinator advised that we would be met in sfo by airbus representative and line maintenance. After parking we left the IRS units in the navigation position so that maintenance would be able to observe the IRS and FMC position. While parked at gate in sfo, a check of the right mcdu position monitor page indicated the following: FMC own: 3737.2N/12223.6W, FMC opp: 3737.2N/12223.4W, radio (blank), IRS mix: 3737.5N/10708.6W. All 3 IRS deviations indicated 99.9 NM.

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Original NASA ASRS Text

Title: A320 ACFT DURING CLB THE MCDU INDICATED 'CHK ACFT POS.' FLC CHKED NAV COMPUTERS AND NOTED THAT ALL 3 IRS DEVS WERE 99 PT 9 MI IN ERROR. FLC ADVISED ATC THAT THEY WERE NO LONGER IRS NAV EQUIPPED. AFTER LNDG AND PARKED AT GATE, THE FMCS WERE VERY ACCURATE BUT IRS' WERE STILL IN ERROR.

Narrative: ON OCT/XX/96, WE WERE ASSIGNED TO FLY FROM ANC TO SFO. AS AN A320 LINE CHK AIRMAN, I OCCUPIED THE R SEAT DURING THIS FLT AND PERFORMED PNF DUTIES, WHILE CONDUCTING IOE WITH CAPT WHO OCCUPIED THE L SEAT AND PERFORMED PF DUTIES DURING THIS FLT. WE ARRIVED AT THE ACFT AT 30 MINS PRIOR TO SCHEDULED DEP. THE TEMP AT THE TIME OF DEP WAS APPROX 17 DEG F. THE ACFT HAD REMAINED OVERNIGHT FOR 13 HRS AND THIS WOULD BE THE FIRST FLT OF THE DAY. UPON ENTERING THE COCKPIT, I TURNED ALL 3 OF THE IRS UNITS FROM THE OFF POS TO NAV AND THEN CONDUCTED A PREFLT EXTERIOR INSPECTION WHILE IOE CAPT A CONDUCTED THE COCKPIT SETUP. THE IRS ALIGNMENT WAS COMPLETED BY CAPT A INITIALIZING THE MCDU (MULTIFUNCTION CTL AND DISPLAY UNIT) PAGE A. THE PRESENT POS WAS INSERTED AS 'PANC' AND THE CORRECT LATITUDE AND LONGITUDE WAS VERIFIED AS THAT SHOWN ON THE COMMERCIAL CHART 10-9 PAGE. DURING THE PREFLT ALL 3 IRS'S ALIGNED NORMALLY AND THE MAP CORRECTLY INDICATED OUR POS ON THE ANCHORAGE ARPT AND IN RELATIONSHIP TO RWY 32 WHICH WAS THE SELECTED DEP RWY. THE TAXI OUT AND TKOF FROM RWY 32 WAS UNEVENTFUL. 2 MINS AFTER TKOF THE MCDU INDICATED 'CHK ACFT POS.' A CHK OF THE R MCDU POS MONITOR PAGE INDICATED THE FOLLOWING: FMC OWN: 6110.3N/14918.9W, FMC OPP: 6110.3N/14919.3W, RADIO 6110.3N/14919.0W, IRS MIX: 61103N/13404.7W, ALL 3 IRS DEVS INDICATED 99.9 NM. A CHK OF ALL 3 IRS UNITS PRESENT POS ON THE OVERHEAD ADIRS CTL DISPLAY UNIT INDICATED THAT ALL 3 UNITS WERE AT 6110.3N/13404.7W WHICH WOULD PUT OUR POS IN THE VICINITY OF THE YXY VOR, SOME 440 MI E OF OUR ACTUAL POS. WE ADVISED ATC WE WERE NOW A 'SLASH ALPHA' EQUIP SUFFIX AND WE PROCEEDED UNEVENTFULLY VIA HIGH ALT AIRWAYS TO SFO. WHILE ENRTE WE CONTACTED DISPATCH, AND MAINT COORDINATOR AND ATTEMPTED TO CONTACT THE A320 FLEET, TO ADVISE THEM OF THIS ANOMALY. MAINT COORDINATOR ADVISED THAT WE WOULD BE MET IN SFO BY AIRBUS REPRESENTATIVE AND LINE MAINT. AFTER PARKING WE LEFT THE IRS UNITS IN THE NAV POS SO THAT MAINT WOULD BE ABLE TO OBSERVE THE IRS AND FMC POS. WHILE PARKED AT GATE IN SFO, A CHK OF THE R MCDU POS MONITOR PAGE INDICATED THE FOLLOWING: FMC OWN: 3737.2N/12223.6W, FMC OPP: 3737.2N/12223.4W, RADIO (BLANK), IRS MIX: 3737.5N/10708.6W. ALL 3 IRS DEVS INDICATED 99.9 NM.

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.