Narrative:

I was on the ILS runway 32 approach into sonoma county airport, cleared by ZOA. The air traffic controller (127.8) said, 'cancel IFR now, or on the ground on this frequency, or call telephone number...'. I was too busy thinking about descending into an undercast, on an ILS approach, with a closed tower, and the ILS was acting funny, low light level, etc and looking up the method for pilot controled runway lights. I heard what the controller said, but did not comprehend the implications of the cancel-options. I thought I'd do him a favor and just cancel while we were in contact, then switch to CTAF 118.5 to get the runway lights on, and advise any other traffic of my intentions and position. I told the controller, 'cancel IFR'. He advised, 'squawk 1200, and contact CTAF on 118.5.' I then proceeded to attempt the ILS approach into the undercast! I felt uncomfortable about having cancelled IFR, and then entering IMC, but was too busy at that point to ponder it further. The tops were about 800' AGL. I discovered that the CDI was not working on the ILS, but the glide slope was. I switched to the VOR runway 32 approach, therefore, which I had already set up on navigation 2. When I reached MDA I could not see the runway, so I executed the published missed approach and contacted ZOA again on 127.8 advising that I was on the missed approach. The controller said, 'I thought you cancelled IFR'. Then it dawned on me that I should not have cancelled. He gave me a new squawk code and I requested another approach, which I got. By now the tower was open. On the handoff, tower advised that ceiling was approximately 100', RVR was about 1000' (both below minimums) and that the ILS alarm was on and was therefore unusable. I aborted the approach and diverted to napa county, which was VFR. During taxi, the ground controller advised that ZOA wanted me to call collect. Did I enter IMC after cancelling IFR? I admitted that I did, and that I realized after the fact that I had made a serious error. The next day, I studied the approach chart in detail and discovered another error. Both the ILS and VOR apches are not authorized when the control zone is not effective (except for operators with approved WX service). Therefore, my first approach attempt was also in violation. It would have helped if the controller had reminded me to maintain VFR when he said, 'squawk 1200 and contact CTAF', like they sometimes do. I think that would have gotten my attention.

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Original NASA ASRS Text

Title: GA PLT CANCELLED IFR CLRNC STARTING AN IAP ILS APCH IN IMC.

Narrative: I WAS ON THE ILS RWY 32 APCH INTO SONOMA COUNTY ARPT, CLRED BY ZOA. THE AIR TFC CTLR (127.8) SAID, 'CANCEL IFR NOW, OR ON THE GND ON THIS FREQ, OR CALL TELEPHONE NUMBER...'. I WAS TOO BUSY THINKING ABOUT DESCENDING INTO AN UNDERCAST, ON AN ILS APCH, WITH A CLOSED TWR, AND THE ILS WAS ACTING FUNNY, LOW LIGHT LEVEL, ETC AND LOOKING UP THE METHOD FOR PLT CTLED RWY LIGHTS. I HEARD WHAT THE CTLR SAID, BUT DID NOT COMPREHEND THE IMPLICATIONS OF THE CANCEL-OPTIONS. I THOUGHT I'D DO HIM A FAVOR AND JUST CANCEL WHILE WE WERE IN CONTACT, THEN SWITCH TO CTAF 118.5 TO GET THE RWY LIGHTS ON, AND ADVISE ANY OTHER TFC OF MY INTENTIONS AND POSITION. I TOLD THE CTLR, 'CANCEL IFR'. HE ADVISED, 'SQUAWK 1200, AND CONTACT CTAF ON 118.5.' I THEN PROCEEDED TO ATTEMPT THE ILS APCH INTO THE UNDERCAST! I FELT UNCOMFORTABLE ABOUT HAVING CANCELLED IFR, AND THEN ENTERING IMC, BUT WAS TOO BUSY AT THAT POINT TO PONDER IT FURTHER. THE TOPS WERE ABOUT 800' AGL. I DISCOVERED THAT THE CDI WAS NOT WORKING ON THE ILS, BUT THE GLIDE SLOPE WAS. I SWITCHED TO THE VOR RWY 32 APCH, THEREFORE, WHICH I HAD ALREADY SET UP ON NAV 2. WHEN I REACHED MDA I COULD NOT SEE THE RWY, SO I EXECUTED THE PUBLISHED MISSED APCH AND CONTACTED ZOA AGAIN ON 127.8 ADVISING THAT I WAS ON THE MISSED APCH. THE CTLR SAID, 'I THOUGHT YOU CANCELLED IFR'. THEN IT DAWNED ON ME THAT I SHOULD NOT HAVE CANCELLED. HE GAVE ME A NEW SQUAWK CODE AND I REQUESTED ANOTHER APCH, WHICH I GOT. BY NOW THE TWR WAS OPEN. ON THE HANDOFF, TWR ADVISED THAT CEILING WAS APPROX 100', RVR WAS ABOUT 1000' (BOTH BELOW MINIMUMS) AND THAT THE ILS ALARM WAS ON AND WAS THEREFORE UNUSABLE. I ABORTED THE APCH AND DIVERTED TO NAPA COUNTY, WHICH WAS VFR. DURING TAXI, THE GND CTLR ADVISED THAT ZOA WANTED ME TO CALL COLLECT. DID I ENTER IMC AFTER CANCELLING IFR? I ADMITTED THAT I DID, AND THAT I REALIZED AFTER THE FACT THAT I HAD MADE A SERIOUS ERROR. THE NEXT DAY, I STUDIED THE APCH CHART IN DETAIL AND DISCOVERED ANOTHER ERROR. BOTH THE ILS AND VOR APCHES ARE NOT AUTHORIZED WHEN THE CTL ZONE IS NOT EFFECTIVE (EXCEPT FOR OPERATORS WITH APPROVED WX SERVICE). THEREFORE, MY FIRST APCH ATTEMPT WAS ALSO IN VIOLATION. IT WOULD HAVE HELPED IF THE CTLR HAD REMINDED ME TO MAINTAIN VFR WHEN HE SAID, 'SQUAWK 1200 AND CONTACT CTAF', LIKE THEY SOMETIMES DO. I THINK THAT WOULD HAVE GOTTEN MY ATTN.

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