Narrative:

At approximately 35 mi from landing at hdn; I was able to pick up the ASOS at hdn and notified ZDV that I would be requesting the ILS runway 10 approach to hdn. I began at this time to set radios for the ILS and requested vectors to the localizer from ATC. At about 13 mi from hdn; I was cleared from center frequency to advisory frequency. At this time I selected the frequency I had previously stored when setting the radios for the approach. I made a position call on advisory frequency and received no reply from unicom which is not too unusual. At 7 mi; made another position report and keyed pilot control lighting to 'high.' at about 2 mi; broke out of the overcast and made a 'short final' position report. It was after this I noticed a rotary snow blower on the taxiway approaching the runway and it appeared he was going to continue onto the runway overrun area. I stopped my descent and lost sight of the plow under the nose of the aircraft. At this point; I noticed another plow on the runway itself and made the decision that I would begin the missed approach. I began a climb but did not immediately begin the turn to the VOR; so I could examine the runway to see if there was some undisclosed hazard or situation to be aware of during my following approach. Not seeing anything; I began my turn on the published missed approach and went to select the center frequency to notify them of the missed approach when I noticed that I had selected the wrong frequency for CTAF 122.8 instead of 123.0 at hdn. I set the correct frequency and called hdn unicom to advise them of the situation. They said they had 'heard me on steamboat's frequency' and were clearing the runway. When they made the call that all the equipment was clear; I was on downwind and had good visual contact with the runway and elected to land from that point. The primary factor in the sequence of events was the pilot's selection of the wrong CTAF. Better awareness of this is the resolution. Additionally issuance of NOTAMS may have reinforced the need to communicate with unicom instead of just make standard position reports. Also a means of monitoring ARTCC might give additional alert of inbound aircraft helping to reduce the chance of similar conflict in a future occurrence of this type.

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Original NASA ASRS Text

Title: C208 PLT IS SURPRISED TO FIND 2 SNOW BLOWERS ON THE RWY AT HDN FOLLOWING AN ILS APCH. ON GAR DISCOVERS HE HAD SELECTED THE WRONG CTAF FREQ. VEHICLES CLRED THE RWY TO ALLOW A SUCCESSFUL LNDG.

Narrative: AT APPROX 35 MI FROM LNDG AT HDN; I WAS ABLE TO PICK UP THE ASOS AT HDN AND NOTIFIED ZDV THAT I WOULD BE REQUESTING THE ILS RWY 10 APCH TO HDN. I BEGAN AT THIS TIME TO SET RADIOS FOR THE ILS AND REQUESTED VECTORS TO THE LOC FROM ATC. AT ABOUT 13 MI FROM HDN; I WAS CLRED FROM CTR FREQ TO ADVISORY FREQ. AT THIS TIME I SELECTED THE FREQ I HAD PREVIOUSLY STORED WHEN SETTING THE RADIOS FOR THE APCH. I MADE A POS CALL ON ADVISORY FREQ AND RECEIVED NO REPLY FROM UNICOM WHICH IS NOT TOO UNUSUAL. AT 7 MI; MADE ANOTHER POS RPT AND KEYED PLT CTL LIGHTING TO 'HIGH.' AT ABOUT 2 MI; BROKE OUT OF THE OVCST AND MADE A 'SHORT FINAL' POS RPT. IT WAS AFTER THIS I NOTICED A ROTARY SNOW BLOWER ON THE TXWY APCHING THE RWY AND IT APPEARED HE WAS GOING TO CONTINUE ONTO THE RWY OVERRUN AREA. I STOPPED MY DSCNT AND LOST SIGHT OF THE PLOW UNDER THE NOSE OF THE ACFT. AT THIS POINT; I NOTICED ANOTHER PLOW ON THE RWY ITSELF AND MADE THE DECISION THAT I WOULD BEGIN THE MISSED APCH. I BEGAN A CLB BUT DID NOT IMMEDIATELY BEGIN THE TURN TO THE VOR; SO I COULD EXAMINE THE RWY TO SEE IF THERE WAS SOME UNDISCLOSED HAZARD OR SITUATION TO BE AWARE OF DURING MY FOLLOWING APCH. NOT SEEING ANYTHING; I BEGAN MY TURN ON THE PUBLISHED MISSED APCH AND WENT TO SELECT THE CTR FREQ TO NOTIFY THEM OF THE MISSED APCH WHEN I NOTICED THAT I HAD SELECTED THE WRONG FREQ FOR CTAF 122.8 INSTEAD OF 123.0 AT HDN. I SET THE CORRECT FREQ AND CALLED HDN UNICOM TO ADVISE THEM OF THE SITUATION. THEY SAID THEY HAD 'HEARD ME ON STEAMBOAT'S FREQ' AND WERE CLRING THE RWY. WHEN THEY MADE THE CALL THAT ALL THE EQUIP WAS CLR; I WAS ON DOWNWIND AND HAD GOOD VISUAL CONTACT WITH THE RWY AND ELECTED TO LAND FROM THAT POINT. THE PRIMARY FACTOR IN THE SEQUENCE OF EVENTS WAS THE PLT'S SELECTION OF THE WRONG CTAF. BETTER AWARENESS OF THIS IS THE RESOLUTION. ADDITIONALLY ISSUANCE OF NOTAMS MAY HAVE REINFORCED THE NEED TO COMMUNICATE WITH UNICOM INSTEAD OF JUST MAKE STANDARD POS RPTS. ALSO A MEANS OF MONITORING ARTCC MIGHT GIVE ADDITIONAL ALERT OF INBOUND ACFT HELPING TO REDUCE THE CHANCE OF SIMILAR CONFLICT IN A FUTURE OCCURRENCE OF THIS TYPE.

Data retrieved from NASA's ASRS site as of January 2009 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.