Narrative:

While operating on a VFR on top clearance, pilot requested vectors to ILS since a visual could not be obtained due to a very thin broken layer over airport area. Pilot was also unfamiliar with exact airport location making a contact approach less feasible with several other large airports nearby. The initial vector to final had about a 100 degree intercept angle. The second vector was issued with simultaneous approach clearance (about 40 degree angle of intercept). Upon obtaining vector heading and acknowledgement pilot noticed that localizer had apparently swung through to the left while the current vector was to the right of course (though course 'swing through' or fly through had not been observed by the pilot). Pilot suspected that some sort of reverse sensing or 'back course' selection may be the cause and briefly checked radios, although a simple check of LOM indication would have been the easiest thing to check. Handoff to tower was about this time and pilot informed the tower he was searching for the ILS. At one point pilot thought the localizer was coming in and began to follow glide slope. (Incidentally, good VFR was really never left as thin layer was broken with good visibility and mostly holes.) a couple of hundred feet down the glide slope pilot saw that the localizer course had probably not been intercepted. Instead of going missed, pilot cancelled the IFR clearance and proceeded visually to the airport since he knew that he was in good VFR and either on course or very close to it. The airport was soon sighted at 12 O'clock and flight completed. A fairly small occurrence, out of which the pilot (with little IFR time) learned many things, two of which are: if unfamiliar with area, ask for 'soft' or 'small' intercept angles, and ask for a 'return vector' if course fly through is suspected.

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Original NASA ASRS Text

Title: IFR SMA IS CLEARED FOR ILS CLOSE IN AND WITH GREATER THAN USUAL INTERCEPT ANGLE, FAILS TO INTERCEPT LOC, AND CANNOT RECOVER THE INSTRUMENT APCH.

Narrative: WHILE OPERATING ON A VFR ON TOP CLRNC, PLT REQUESTED VECTORS TO ILS SINCE A VISUAL COULD NOT BE OBTAINED DUE TO A VERY THIN BROKEN LAYER OVER ARPT AREA. PLT WAS ALSO UNFAMILIAR WITH EXACT ARPT LOCATION MAKING A CONTACT APCH LESS FEASIBLE WITH SEVERAL OTHER LARGE ARPTS NEARBY. THE INITIAL VECTOR TO FINAL HAD ABOUT A 100 DEG INTERCEPT ANGLE. THE SECOND VECTOR WAS ISSUED WITH SIMULTANEOUS APCH CLRNC (ABOUT 40 DEG ANGLE OF INTERCEPT). UPON OBTAINING VECTOR HDG AND ACKNOWLEDGEMENT PLT NOTICED THAT LOC HAD APPARENTLY SWUNG THROUGH TO THE LEFT WHILE THE CURRENT VECTOR WAS TO THE RIGHT OF COURSE (THOUGH COURSE 'SWING THROUGH' OR FLY THROUGH HAD NOT BEEN OBSERVED BY THE PLT). PLT SUSPECTED THAT SOME SORT OF REVERSE SENSING OR 'BACK COURSE' SELECTION MAY BE THE CAUSE AND BRIEFLY CHECKED RADIOS, ALTHOUGH A SIMPLE CHECK OF LOM INDICATION WOULD HAVE BEEN THE EASIEST THING TO CHECK. HANDOFF TO TWR WAS ABOUT THIS TIME AND PLT INFORMED THE TWR HE WAS SEARCHING FOR THE ILS. AT ONE POINT PLT THOUGHT THE LOC WAS COMING IN AND BEGAN TO FOLLOW GLIDE SLOPE. (INCIDENTALLY, GOOD VFR WAS REALLY NEVER LEFT AS THIN LAYER WAS BROKEN WITH GOOD VISIBILITY AND MOSTLY HOLES.) A COUPLE OF HUNDRED FEET DOWN THE GLIDE SLOPE PLT SAW THAT THE LOC COURSE HAD PROBABLY NOT BEEN INTERCEPTED. INSTEAD OF GOING MISSED, PLT CANCELLED THE IFR CLRNC AND PROCEEDED VISUALLY TO THE ARPT SINCE HE KNEW THAT HE WAS IN GOOD VFR AND EITHER ON COURSE OR VERY CLOSE TO IT. THE ARPT WAS SOON SIGHTED AT 12 O'CLOCK AND FLT COMPLETED. A FAIRLY SMALL OCCURRENCE, OUT OF WHICH THE PLT (WITH LITTLE IFR TIME) LEARNED MANY THINGS, TWO OF WHICH ARE: IF UNFAMILIAR WITH AREA, ASK FOR 'SOFT' OR 'SMALL' INTERCEPT ANGLES, AND ASK FOR A 'RETURN VECTOR' IF COURSE FLY THROUGH IS SUSPECTED.

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.