An air carrier B767 flight crew experienced a map shift and began to use manual control of the aircr...

Attributes
ACN	398620
Time
Date	199804
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : lax
State Reference	CA
Altitude	msl bound lower : 3500 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	B767-200
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 16000 flight time type : 800
ASRS Report	398620
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : crossing restriction not met non adherence : clearance non adherence : far non adherence : published procedure other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : detected after the fact other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

On approach to lax for runway 25L ILS, there was a map shift which moved the track line about 1 mi right of course. This happened at approximately 10000 ft passing arnes intersection, and just before changing from LNAV to localizer mode for navigation tracking. I disconnected the autoplt when the aircraft started turning to the displaced track line, engaged localizer mode and attempted to use the flight director to intercept the inbound ILS track. The flight director did not provide proper guidance and so I flew raw data to get back on centerline. This occurred in the vicinity of several crossing fixes on the approach, namely suzzi, gaate, etc. As a result of distraction, 1 or more of those fixes were crossed approximately 200 ft below the published crossing altitudes. There was no known traffic conflict. When established on the localizer, the flight director began to perform normally and the track line slowly moved back to a position co-incident with the localizer centerline, but the indicated track on both HSI's was off about 15 degrees from actual track. On touchdown, the HSI track slewed to inbound course. The system malfunction was written up in the aircraft logbook and company management was verbally debriefed regarding the track shift and the map shift. The reason for the malfunction is not known at this time. The situation was exacerbated by the complexity of the approach (large number of stepdown fixes and need to verify DME distance of each), ATC speed restr and communication with ATC which was relative to traffic on the runway 24R visual approach. It is a high workload approach because of the complexity. A lesser number of stepdown fixes or ability to use GS further from runway could help improve the approach. Callback conversation with reporter revealed the following information: the reporter said that he had called his company maintenance personnel to discover the cause of the map shift and other problems with the FMC, but they had not responded yet. He said that he would call ASRS with the information when it was available.

Original NASA ASRS Text

Title: AN ACR B767 FLC EXPERIENCED A MAP SHIFT AND BEGAN TO USE MANUAL CTL OF THE ACFT WITH REF TO THE APCH RAW DATA INFO. HOWEVER, THEY DID NOT REALIZE THAT THE DESIGNATED ALTS AT THE XING POINTS DO NOT NECESSARILY COINCIDE WITH THE GS ALTS AT EACH POINT. THE FLT PATH WAS AS MUCH AS 200 FT LOW AT SOME OF THE XING POINTS.

Narrative: ON APCH TO LAX FOR RWY 25L ILS, THERE WAS A MAP SHIFT WHICH MOVED THE TRACK LINE ABOUT 1 MI R OF COURSE. THIS HAPPENED AT APPROX 10000 FT PASSING ARNES INTXN, AND JUST BEFORE CHANGING FROM LNAV TO LOC MODE FOR NAV TRACKING. I DISCONNECTED THE AUTOPLT WHEN THE ACFT STARTED TURNING TO THE DISPLACED TRACK LINE, ENGAGED LOC MODE AND ATTEMPTED TO USE THE FLT DIRECTOR TO INTERCEPT THE INBOUND ILS TRACK. THE FLT DIRECTOR DID NOT PROVIDE PROPER GUIDANCE AND SO I FLEW RAW DATA TO GET BACK ON CTRLINE. THIS OCCURRED IN THE VICINITY OF SEVERAL XING FIXES ON THE APCH, NAMELY SUZZI, GAATE, ETC. AS A RESULT OF DISTR, 1 OR MORE OF THOSE FIXES WERE CROSSED APPROX 200 FT BELOW THE PUBLISHED XING ALTS. THERE WAS NO KNOWN TFC CONFLICT. WHEN ESTABLISHED ON THE LOC, THE FLT DIRECTOR BEGAN TO PERFORM NORMALLY AND THE TRACK LINE SLOWLY MOVED BACK TO A POS CO-INCIDENT WITH THE LOC CTRLINE, BUT THE INDICATED TRACK ON BOTH HSI'S WAS OFF ABOUT 15 DEGS FROM ACTUAL TRACK. ON TOUCHDOWN, THE HSI TRACK SLEWED TO INBOUND COURSE. THE SYS MALFUNCTION WAS WRITTEN UP IN THE ACFT LOGBOOK AND COMPANY MGMNT WAS VERBALLY DEBRIEFED REGARDING THE TRACK SHIFT AND THE MAP SHIFT. THE REASON FOR THE MALFUNCTION IS NOT KNOWN AT THIS TIME. THE SIT WAS EXACERBATED BY THE COMPLEXITY OF THE APCH (LARGE NUMBER OF STEPDOWN FIXES AND NEED TO VERIFY DME DISTANCE OF EACH), ATC SPD RESTR AND COM WITH ATC WHICH WAS RELATIVE TO TFC ON THE RWY 24R VISUAL APCH. IT IS A HIGH WORKLOAD APCH BECAUSE OF THE COMPLEXITY. A LESSER NUMBER OF STEPDOWN FIXES OR ABILITY TO USE GS FURTHER FROM RWY COULD HELP IMPROVE THE APCH. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THAT HE HAD CALLED HIS COMPANY MAINT PERSONNEL TO DISCOVER THE CAUSE OF THE MAP SHIFT AND OTHER PROBS WITH THE FMC, BUT THEY HAD NOT RESPONDED YET. HE SAID THAT HE WOULD CALL ASRS WITH THE INFO WHEN IT WAS AVAILABLE.

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.