Narrative:

Simulated land 3 on B767 runway 14R ord cavu day. All txwys were clear and free of aircraft. We were following a regional jet at about 2 1/2 - 3 mi. We experienced a slight localizer deviation when the regional jet exited the runway ahead as is typical. On short final approach; I noticed a freight train with 3 locomotives pass under our nose left to right. Aircraft continued to track centered on both localizer and GS but visually I could see aircraft started right and increased descent to the point where I was getting very uncomfortable about where it was heading which appeared to be well right of centerline. Just when I was going to disconnect and take over manually; flare mode annunciated and aircraft leveled off slightly and added a touch of power and returned to centerline for a typical autoland landing and rollout tracked centerline nicely. Note aircraft tracked a centered ILS continuously. I believe the freight train caused a deviation in the localizer and GS which influenced it to the right and down. The geometry of the ILS location and proximity and angle of the tracks in combination with the locomotive engines which are a large mass of steel; diesel engines and huge electrical generators influenced the ILS. In the wrong combination of atmospheric conditions and timing of train movement and an aircraft ILS approach could lead to a centered ILS landing off the runway.

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Original NASA ASRS Text

Title: A B767-300 CONDUCTING A PRACTICE LAND 3 TO ORD RWY 14R EXPERIENCED A SLIGHT CTRLINE TRACKING DEV AS A TRAIN PASSED BENEATH THE ACFT.

Narrative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

Data retrieved from NASA's ASRS site as of January 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.