Narrative:

Started out with heavy snowfall and low visibilities across the state of montana. My first flight was cancelled due to low visibility at my destination. Second flight delayed due to low visibility at my departure airport. I was deiced 3 times before I got off the ground the first time. After making my first flight to kalispell, I waited on the ground for conditions to improve for my next flight to helena. When I finally took off, visibility in helena had come up to 1 1/2 mi and I planned on shooting the ILS to runway 27, which would be the safest and easiest approach. My nearest alternate that day was spokane, wa. En route, I was experiencing moderate rime icing and needed to inflate the boots periodically, not a fun day. Helena ATIS said to expect the ILS runway 27 approach, which was what I had planned on and what I had prepared for. My intent was to fly direct to the VOR, then follow the localizer 'back course' out, do the procedure turn and intercept the localizer inbound to runway 27. At 22 DME, salt lake center handed me over to helena approach. When I contacted helena, I requested the 'ILS runway 27' approach. This is where the misunderstanding took place. Helena approach said 'how about the localizer back course circle to land runway 27?' my brain heard what it expected to hear, namely 'back course' and '27.' I replied back 'cleared for the ILS runway 27 approach' at which time the controller's brain heard what he expected to hear. Next, he cleared me to 9500 ft and told me to intercept the 13 DME arc. Now this part had me curious, but the ILS runway 27 does happen to have a 15 mi arc, so I assumed he was changing my approach to fly the arc around to the localizer and had changed to 13 DME due to my near proximity by this time (my approach was from the north west). I also started experiencing moderate turbulence and mod mixed icing, so my hands were full, plus I needed to concentrate on flying a good arc and making sure I was ready for the approach. Neither he nor I realized there was a problem until he asked me where I was on the arc. I replied that I was on the 20 degree radial. He said, 'so you are out to the northwest?' I said, 'no, to the northeast.' he then cleared me for the ILS to runway 27, but I sighted the airport and finished up with a visual. The only other aircraft in the area at the time was an air carrier aircraft, which was coming in from the east and was told to hold while I finished the approach I was on, but was able to proceed directly in after I headed straight to the runway. I have no excuses other than being tired after 8 hours of dealing with inclement WX. Funny thing is that if I had understood the clearance correctly, I would have had to decline due to the fact that I was too close in to make the change. Also, that particular approach would have only gotten me down to 1246 ft AGL and wouldn't have been my first choice on that particular day.

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Original NASA ASRS Text

Title: CESSNA 208 CARGO PLT MISTAKENLY MADE THE ASSIGNED DME ARC ON GOING AROUND TO THE ILS INSTEAD OF THE BACK COURSE TO WHICH HE WAS ASSIGNED.

Narrative: STARTED OUT WITH HVY SNOWFALL AND LOW VISIBILITIES ACROSS THE STATE OF MONTANA. MY FIRST FLT WAS CANCELLED DUE TO LOW VISIBILITY AT MY DEST. SECOND FLT DELAYED DUE TO LOW VIS AT MY DEP ARPT. I WAS DEICED 3 TIMES BEFORE I GOT OFF THE GND THE FIRST TIME. AFTER MAKING MY FIRST FLT TO KALISPELL, I WAITED ON THE GROUND FOR CONDITIONS TO IMPROVE FOR MY NEXT FLT TO HELENA. WHEN I FINALLY TOOK OFF, VISIBILITY IN HELENA HAD COME UP TO 1 1/2 MI AND I PLANNED ON SHOOTING THE ILS TO RWY 27, WHICH WOULD BE THE SAFEST AND EASIEST APCH. MY NEAREST ALTERNATE THAT DAY WAS SPOKANE, WA. ENRTE, I WAS EXPERIENCING MODERATE RIME ICING AND NEEDED TO INFLATE THE BOOTS PERIODICALLY, NOT A FUN DAY. HELENA ATIS SAID TO EXPECT THE ILS RWY 27 APCH, WHICH WAS WHAT I HAD PLANNED ON AND WHAT I HAD PREPARED FOR. MY INTENT WAS TO FLY DIRECT TO THE VOR, THEN FOLLOW THE LOC 'BACK COURSE' OUT, DO THE PROC TURN AND INTERCEPT THE LOC INBOUND TO RWY 27. AT 22 DME, SALT LAKE CTR HANDED ME OVER TO HELENA APCH. WHEN I CONTACTED HELENA, I REQUESTED THE 'ILS RWY 27' APCH. THIS IS WHERE THE MISUNDERSTANDING TOOK PLACE. HELENA APCH SAID 'HOW ABOUT THE LOC BACK COURSE CIRCLE TO LAND RWY 27?' MY BRAIN HEARD WHAT IT EXPECTED TO HEAR, NAMELY 'BACK COURSE' AND '27.' I REPLIED BACK 'CLRED FOR THE ILS RWY 27 APCH' AT WHICH TIME THE CTLR'S BRAIN HEARD WHAT HE EXPECTED TO HEAR. NEXT, HE CLRED ME TO 9500 FT AND TOLD ME TO INTERCEPT THE 13 DME ARC. NOW THIS PART HAD ME CURIOUS, BUT THE ILS RWY 27 DOES HAPPEN TO HAVE A 15 MI ARC, SO I ASSUMED HE WAS CHANGING MY APCH TO FLY THE ARC AROUND TO THE LOC AND HAD CHANGED TO 13 DME DUE TO MY NEAR PROX BY THIS TIME (MY APCH WAS FROM THE N WEST). I ALSO STARTED EXPERIENCING MODERATE TURB AND MOD MIXED ICING, SO MY HANDS WERE FULL, PLUS I NEEDED TO CONCENTRATE ON FLYING A GOOD ARC AND MAKING SURE I WAS READY FOR THE APCH. NEITHER HE NOR I REALIZED THERE WAS A PROB UNTIL HE ASKED ME WHERE I WAS ON THE ARC. I REPLIED THAT I WAS ON THE 20 DEG RADIAL. HE SAID, 'SO YOU ARE OUT TO THE NW?' I SAID, 'NO, TO THE NE.' HE THEN CLRED ME FOR THE ILS TO RWY 27, BUT I SIGHTED THE ARPT AND FINISHED UP WITH A VISUAL. THE ONLY OTHER ACFT IN THE AREA AT THE TIME WAS AN ACR ACFT, WHICH WAS COMING IN FROM THE E AND WAS TOLD TO HOLD WHILE I FINISHED THE APCH I WAS ON, BUT WAS ABLE TO PROCEED DIRECTLY IN AFTER I HEADED STRAIGHT TO THE RWY. I HAVE NO EXCUSES OTHER THAN BEING TIRED AFTER 8 HRS OF DEALING WITH INCLEMENT WX. FUNNY THING IS THAT IF I HAD UNDERSTOOD THE CLRNC CORRECTLY, I WOULD HAVE HAD TO DECLINE DUE TO THE FACT THAT I WAS TOO CLOSE IN TO MAKE THE CHANGE. ALSO, THAT PARTICULAR APCH WOULD HAVE ONLY GOTTEN ME DOWN TO 1246 FT AGL AND WOULDN'T HAVE BEEN MY FIRST CHOICE ON THAT PARTICULAR DAY.

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.