Narrative:

Pre departure clearance clearance assigned watsn one arrival; rod transition into ord. Initially received ATIS indicated only ILS 28 in use. About 120 miles before TOD briefed watsn one arrival and set up/briefed ILS 28. When new ATIS indicated ILS 27L also in use also briefed that approach and set ILS 27L frequency in standby window of both navigation radios (ILS 28 frequency set in active window both navs) approaching rod chicago center cleared flight direct mzz and the royko three arrival. This change seemed to confirm ILS 28 as most likely approach so kept FMC; frequencies; bugs etc. Setup for 28. Somewhere in the vicinity of cluso center changed arrival back to the watsn one and cleared flight direct to watsn. [I] thought about changing approach set up to 27L; but decision interrupted by center clearing us to cross 5 miles before hulls at 12;000 ft; just as aircraft reached TOD for crossing hulls at 12;000 ft so had to work at meeting tighter crossing restriction. Also since neither arrival is runway(s) specific decided to leave ILS 28 set up until approach assigned runway. After hulls [center] handed off to ord approach. Upon initial contact no explicit runway assignment. [I] could have asked; but approach control [was] busy. [We were] cleared down to 11;000 ft. Then close to dweeb (about 45 miles from ord) cleared to 10;000 ft and assigned heading to intercept localizer 27L. [We] changed the approach to 27L in the FMC. First officer said he was identifying the localizer. Ironically thought about intercepting localizer in LNAV since intercept point would be 20 miles or so from runway but needed to extend localizer path first. At this point crews activities changing runway and approach set up was interrupted by approach control inquiry concerning speed. Much earlier center had assigned 300 KTS. [I] am aware of ord approach expectations that aircraft keep the speed up until assigned otherwise. However since using MCP to control aircraft had made mental note to slow to 250 when cleared to descend from 11;000 ft. When cleared by approach to 10;000 ft missed the subtlety that could still maintain 300 KTS at 10;000 ft but not below so slowed to 250. Approach asked if we were still doing 300 KTS. When told 250 KTS approach patiently explained ord expected aircraft to maintain assigned speed; then cleared us to 7;000 ft and repeated clearance to join 27L localizer. At about this point selected VOR localizer to make sure we did not miss the localizer. Called for the approach checklist which included identifying the radios. As it became clear latter in the midst of all the above activity the first officer (who is one of the best) apparently used the ILS28 approach plate for the morse code identification of the ILS frequency. Neither one of us noticed that we had not switched the ILS 27L frequency from standby to active so that the ILS 28 frequency was still active in both navigation receivers. As a result VOR localizer engaged and the ac joined ILS 28 course instead of the intended ILS 27L about 20 to 25 miles east of the runway. The ehsi needle indicated centered on the localizer; but did notice that on the FMC map the aircraft was not centered on the now extended magenta ILS 27L course line. With I believe a 20 mile scale on the map the aircraft position on the map did not seem that far off and my belief that the ac was centered on the proper localizer signal was reinforced by the thought in the back of my mind that radios were identified so I did not immediately do what in retrospect seems so obvious; namely check the frequency in the active navigation windows or expand the map to realize we were well south of the magenta line. While still pondering the anomaly ;which I was beginning to verbalize; not that long after joining the 28 localizer; ord approach called to report we flying the 28 localizer and directed us to fly a 300 heading and join the 27L localizer. We were then cleared for the ILS 27L and landed runway 27L without further incidents.

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Original NASA ASRS Text

Title: ZAU ATC changed an air carrier aircraft's ORD arrival several times as they approached from the east. The flight crew assumed their runway would be 28; but upon capturing the 28 LOC; ORD Approach stated they were cleared for the 27L Approach.

Narrative: PDC clearance assigned WATSN ONE arrival; ROD transition into ORD. Initially received ATIS indicated only ILS 28 in use. About 120 miles before TOD briefed WATSN ONE arrival and set up/briefed ILS 28. When new ATIS indicated ILS 27L also in use also briefed that approach and set ILS 27L frequency in standby window of both NAV radios (ILS 28 frequency set in active window both NAVs) approaching ROD Chicago Center cleared flight direct MZZ and the ROYKO THREE arrival. This change seemed to confirm ILS 28 as most likely approach so kept FMC; frequencies; bugs etc. setup for 28. Somewhere in the vicinity of CLUSO Center changed arrival back to the WATSN ONE and cleared flight direct to WATSN. [I] thought about changing approach set up to 27L; but decision interrupted by Center clearing us to cross 5 miles before HULLS at 12;000 FT; just as aircraft reached TOD for crossing HULLS at 12;000 FT so had to work at meeting tighter crossing restriction. Also since neither arrival is runway(s) specific decided to leave ILS 28 set up until Approach assigned runway. After HULLS [Center] handed off to ORD Approach. Upon initial contact no explicit runway assignment. [I] could have asked; but Approach Control [was] busy. [We were] cleared down to 11;000 FT. Then close to DWEEB (about 45 miles from ORD) cleared to 10;000 FT and assigned heading to intercept LOC 27L. [We] changed the approach to 27L in the FMC. First Officer said he was identifying the LOC. Ironically thought about intercepting LOC in LNAV since intercept point would be 20 miles or so from runway but needed to extend LOC path first. At this point crews activities changing runway and approach set up was interrupted by Approach Control inquiry concerning speed. Much earlier Center had assigned 300 KTS. [I] am aware of ORD Approach expectations that aircraft keep the speed up until assigned otherwise. However since using MCP to control aircraft had made mental note to slow to 250 when cleared to descend from 11;000 FT. When cleared by Approach to 10;000 FT missed the subtlety that could still maintain 300 KTS at 10;000 FT but not below so slowed to 250. Approach asked if we were still doing 300 KTS. When told 250 KTS Approach patiently explained ORD expected aircraft to maintain assigned speed; then cleared us to 7;000 FT and repeated clearance to join 27L LOC. AT about this point selected VOR LOC to make sure we did not miss the LOC. Called for the Approach Checklist which included identifying the radios. As it became clear latter in the midst of all the above activity the First Officer (who is one of the best) apparently used the ILS28 Approach plate for the Morse Code identification of the ILS frequency. Neither one of us noticed that we had not switched the ILS 27L frequency from standby to active so that the ILS 28 frequency was still active in both NAV receivers. As a result VOR LOC engaged and the ac joined ILS 28 course instead of the intended ILS 27L about 20 to 25 miles east of the runway. The EHSI needle indicated centered on the LOC; but did notice that on the FMC map the aircraft was not centered on the now extended magenta ILS 27L course line. With I believe a 20 mile scale on the map the aircraft position on the map did not seem that far off and my belief that the ac was centered on the proper LOC signal was reinforced by the thought in the back of my mind that radios were identified so I did not immediately do what in retrospect seems so obvious; namely check the frequency in the active NAV windows or expand the map to realize we were well south of the magenta line. While still pondering the anomaly ;which I was beginning to verbalize; not that long after joining the 28 LOC; ORD Approach called to report we flying the 28 LOC and directed us to fly a 300 heading and join the 27L LOC. We were then cleared for the ILS 27L and landed Runway 27L without further incidents.

Data retrieved from NASA's ASRS site as of July 2013 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.