Air carrier flight crew reported a discrepancy between the ILS and their navigation display causing ...

Attributes
ACN	1533123
Time
Date	201804
Local Time Of Day	0001-0600
Place
Locale Reference	SMF.Airport
State Reference	CA
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	Widebody Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	STAR SLMMR 1
Flight Plan	IFR
Component
Aircraft Component	Navigational Equipment and Processing
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Aircraft Equipment Problem Less Severe Deviation - Procedural Clearance Deviation - Track / Heading All Types

Narrative:

Given slmmr one RNAV arrival. At fix tenco given feeder route to fapin intersection cleared ILS 16L. Given the sharp intercept angle; I planned to use LNAV to intercept the localizer. The aircraft started turn to intersect and ATC asked where I was going. We told them turning to intercept the localizer; but was not receiving it. He told us to go missed and were given a heading and altitude. We complied with the instructions. Checked all our settings for the approach [and] they were all correct.the first officer was monitoring the raw data on lower screen and had tuned and identified the fix as per standard procedures. When given a heading to re-intercept the localizer; the heading showed us intercepting inside the FAF. I asked for a new heading. Just as we started a further turn right the localizer captured. The FMC showed the localizer extension line 1.5 to 2 miles to the right. As we flew down the localizer the two lines slowly merged. We landed safely.there has been multiple reports from other pilots of this happening to legacy equipped aircraft at smf. Until we find out why this is happening we should send GPS aircraft to this location. Speculation is the DME to DME update is causing a map shift late in the arrival. We were never shown off the arrival or notified we were.

Original NASA ASRS Text

Title: Air carrier flight crew reported a discrepancy between the ILS and their navigation display causing conflicting and confusing information.

Narrative: Given SLMMR ONE RNAV Arrival. At fix TENCO given feeder route to FAPIN intersection cleared ILS 16L. Given the sharp intercept angle; I planned to use LNAV to intercept the localizer. The aircraft started turn to intersect and ATC asked where I was going. We told them turning to intercept the localizer; but was not receiving it. He told us to go missed and were given a heading and altitude. We complied with the instructions. Checked all our settings for the approach [and] they were all correct.The First Officer was monitoring the raw data on lower screen and had tuned and identified the fix as per standard procedures. When given a heading to re-intercept the localizer; the heading showed us intercepting inside the FAF. I asked for a new heading. Just as we started a further turn right the localizer captured. The FMC showed the localizer extension line 1.5 to 2 miles to the right. As we flew down the localizer the two lines slowly merged. We landed safely.There has been multiple reports from other pilots of this happening to legacy equipped aircraft at SMF. Until we find out why this is happening we should send GPS aircraft to this location. Speculation is the DME to DME update is causing a map shift late in the arrival. We were never shown off the arrival or notified we were.

Data retrieved from NASA's ASRS site 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.