Narrative:

Departed san luis obispo airport with avila two departure, morrow bay transition. After contacting ZLA, told to do avila two departure. Replied I understood. Intercepted mqo 306 radial and tracked inbound at avila intersection. Asked the heading by ZLA. Told them 305 degree. Told to turn to 180, best climb. I complied. Told that my clearance had been amended to gaviota transition and I had acknowledged. I did not understand that it was an amended clearance at the time, and I had not read it back. I had said only that I understood. This was done as I thought I had received only a repeat by ZLA on my previously received and read back clearance. ZLA also told me that I had not flown to avila intersection. While on the 180 degree vector, I started to suspect my #1 VOR receiver, and I checked it against #2 VOR. Found #1 VOR did not agree with #2 VOR. This was unexpected as I had done a VOR receiver xchk earlier in the day, and I had used both receivers only an hour and a half before while coming into san luis obispo under IMC on an IFR flight plan, and they worked fine then. I told ZLA that I had not understood that my clearance had been amended earlier and that I had a VOR receiver problem that I had not detected until just now. By now the airplane was getting well over the ocean, and I asked center if they still wanted me on the 180 degree heading. He said no and gave instructions which brought us back over land. Problems: 1) while executing a SID, at night while IFR, center told me to fly a different departure. I was so fully occupied that I did not hear all of the instruction. When I did not read it back, ZLA should have repeated the amended clearance. 2) one of my VOR receivers failed unexpectedly and seemed to be giving a proper reading. 3) if I had understood that my clearance had been amended, my workload was so high at the time that I could not have flown it immediately. That would have required reading it in the SID book (which I had open to right page), changing the VOR receiver to another station and course and flying it. Under the pressure of a night IMC departure, that would have taken me more than a minute, and would have placed my aircraft in possible hazard. If I had understood that my clearance was being amended in a way that made my workload too great to comply in a timely manner, I would have asked for radar vectors while setting up the SID, or in the event that was not available, I would have asked to return and land using the localizer approach which I had studied and flown a short time before.

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Original NASA ASRS Text

Title: SMA ON NIGHT IFR FLT IN IMC EXPERIENCES RADIO NAVIGATION PROBLEM CLRNC CONFUSION AND FAILS TO FLY ATC CLRNC.

Narrative: DEPARTED SAN LUIS OBISPO ARPT WITH AVILA TWO DEP, MORROW BAY TRANSITION. AFTER CONTACTING ZLA, TOLD TO DO AVILA TWO DEP. REPLIED I UNDERSTOOD. INTERCEPTED MQO 306 RADIAL AND TRACKED INBND AT AVILA INTXN. ASKED THE HDG BY ZLA. TOLD THEM 305 DEG. TOLD TO TURN TO 180, BEST CLIMB. I COMPLIED. TOLD THAT MY CLRNC HAD BEEN AMENDED TO GAVIOTA TRANSITION AND I HAD ACKNOWLEDGED. I DID NOT UNDERSTAND THAT IT WAS AN AMENDED CLRNC AT THE TIME, AND I HAD NOT READ IT BACK. I HAD SAID ONLY THAT I UNDERSTOOD. THIS WAS DONE AS I THOUGHT I HAD RECEIVED ONLY A REPEAT BY ZLA ON MY PREVIOUSLY RECEIVED AND READ BACK CLRNC. ZLA ALSO TOLD ME THAT I HAD NOT FLOWN TO AVILA INTXN. WHILE ON THE 180 DEG VECTOR, I STARTED TO SUSPECT MY #1 VOR RECEIVER, AND I CHECKED IT AGAINST #2 VOR. FOUND #1 VOR DID NOT AGREE WITH #2 VOR. THIS WAS UNEXPECTED AS I HAD DONE A VOR RECEIVER XCHK EARLIER IN THE DAY, AND I HAD USED BOTH RECEIVERS ONLY AN HOUR AND A HALF BEFORE WHILE COMING INTO SAN LUIS OBISPO UNDER IMC ON AN IFR FLT PLAN, AND THEY WORKED FINE THEN. I TOLD ZLA THAT I HAD NOT UNDERSTOOD THAT MY CLRNC HAD BEEN AMENDED EARLIER AND THAT I HAD A VOR RECEIVER PROBLEM THAT I HAD NOT DETECTED UNTIL JUST NOW. BY NOW THE AIRPLANE WAS GETTING WELL OVER THE OCEAN, AND I ASKED CENTER IF THEY STILL WANTED ME ON THE 180 DEG HDG. HE SAID NO AND GAVE INSTRUCTIONS WHICH BROUGHT US BACK OVER LAND. PROBLEMS: 1) WHILE EXECUTING A SID, AT NIGHT WHILE IFR, CENTER TOLD ME TO FLY A DIFFERENT DEP. I WAS SO FULLY OCCUPIED THAT I DID NOT HEAR ALL OF THE INSTRUCTION. WHEN I DID NOT READ IT BACK, ZLA SHOULD HAVE REPEATED THE AMENDED CLRNC. 2) ONE OF MY VOR RECEIVERS FAILED UNEXPECTEDLY AND SEEMED TO BE GIVING A PROPER READING. 3) IF I HAD UNDERSTOOD THAT MY CLRNC HAD BEEN AMENDED, MY WORKLOAD WAS SO HIGH AT THE TIME THAT I COULD NOT HAVE FLOWN IT IMMEDIATELY. THAT WOULD HAVE REQUIRED READING IT IN THE SID BOOK (WHICH I HAD OPEN TO RIGHT PAGE), CHANGING THE VOR RECEIVER TO ANOTHER STATION AND COURSE AND FLYING IT. UNDER THE PRESSURE OF A NIGHT IMC DEP, THAT WOULD HAVE TAKEN ME MORE THAN A MINUTE, AND WOULD HAVE PLACED MY ACFT IN POSSIBLE HAZARD. IF I HAD UNDERSTOOD THAT MY CLRNC WAS BEING AMENDED IN A WAY THAT MADE MY WORKLOAD TOO GREAT TO COMPLY IN A TIMELY MANNER, I WOULD HAVE ASKED FOR RADAR VECTORS WHILE SETTING UP THE SID, OR IN THE EVENT THAT WAS NOT AVAILABLE, I WOULD HAVE ASKED TO RETURN AND LAND USING THE LOC APCH WHICH I HAD STUDIED AND FLOWN A SHORT TIME BEFORE.

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.