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

SIMULATED LAND 3 ON B767 RWY 14R ORD CAVU DAY. ALL TXWYS WERE CLR AND FREE OF ACFT. WE WERE FOLLOWING A REGIONAL JET AT ABOUT 2 1/2 - 3 MI. WE EXPERIENCED A SLIGHT LOC DEV WHEN THE REGIONAL JET EXITED THE RWY AHEAD AS IS TYPICAL. ON SHORT FINAL APCH; I NOTICED A FREIGHT TRAIN WITH 3 LOCOMOTIVES PASS UNDER OUR NOSE L TO R. ACFT CONTINUED TO TRACK CTRED ON BOTH LOC AND GS BUT VISUALLY I COULD SEE ACFT STARTED R AND INCREASED DSCNT TO THE POINT WHERE I WAS GETTING VERY UNCOMFORTABLE ABOUT WHERE IT WAS HEADING WHICH APPEARED TO BE WELL R OF CTRLINE. JUST WHEN I WAS GOING TO DISCONNECT AND TAKE OVER MANUALLY; FLARE MODE ANNUNCIATED AND ACFT LEVELED OFF SLIGHTLY AND ADDED A TOUCH OF PWR AND RETURNED TO CTRLINE FOR A TYPICAL AUTOLAND LNDG AND ROLLOUT TRACKED CTRLINE NICELY. NOTE ACFT TRACKED A CTRED ILS CONTINUOUSLY. I BELIEVE THE FREIGHT TRAIN CAUSED A DEV IN THE LOC AND GS WHICH INFLUENCED IT TO THE R AND DOWN. THE GEOMETRY OF THE ILS LOCATION AND PROX AND ANGLE OF THE TRACKS IN COMBINATION WITH THE LOCOMOTIVE ENGS WHICH ARE A LARGE MASS OF STEEL; DIESEL ENGS AND HUGE ELECTRICAL GENERATORS INFLUENCED THE ILS. IN THE WRONG COMBINATION OF ATMOSPHERIC CONDITIONS AND TIMING OF TRAIN MOVEMENT AND AN ACFT ILS APCH COULD LEAD TO A CTRED ILS LNDG OFF THE RWY.