Narrative:

I reported for duty, checked in with dispatch, and called for a WX briefing with FSS. I then proceeded outside and performed a preflight aircraft check. While performing the preflight, I observed a thin layer of frost (less than 1/32 inch thick) covering the windscreen and portions of the aircraft (approximately 25% of the aircraft was covered with frost). While wearing a glove, I dragged a finger across the windscreen and easily cleared an area free of frost, while noting its thickness. I elected not to deice the aircraft with fluid and chose to defrost the windscreen with environmental heat, and electrically defrost the hot plate. 5 mins prior to load completion, I called for clearance and turned on the windshield anti-ice for approximately 60 seconds, clearing the hot plate from frost. After loading was complete, I secured the cargo door and chocks and was ready for engine start. I called ground for taxi and was cleared for taxi to runway 19R. I was marshaled out of my spot and began taxiing slowly to runway 19R with all available heat on the windscreen. The route I chose to runway 19R was approximately 800-1000 ft total taxi distance. However, while taxiing, cargo ramp lighting and my aircraft taxi lights were causing a glare effect on the frosty windscreen. The aircraft left the hard surfaced cargo area. I immediately applied brakes and stopped, coming to rest in a grassy area between the cargo ramp (west of) and taxiway D (east of). I immediately informed ground control that I was in the grass west of the cargo ramp. They replied 'ok' and again asked for my position. I replied with my position and asked them to hold on so I could assess the situation. I then opened the pilot's door and turned on all forward lighting to see the area better. The grass was cut short and the grade of the area was such that I had no concern of a propeller strike. I informed ground that I needed to make a 180 degree turn to return to the cargo ramp area, and they approved my request. However, prior to moving the aircraft, I noticed a drainage grate approximately 10 ft to the left of my aircraft (south of my position) and feared collapsing the grate if coming in contact with it. I then informed ground that the area ahead of me was clear and asked to taxi straight ahead to taxiway D. They approved my request, and I taxied slowly ahead through approximately 50 ft of grass and returned to hard surface on taxiway D. I continued to runway 19R and called tower short of runway 19R and requested a short delay. I then performed an overspd governor check and rechked the PAR unit for any exceedences in engine parameters. I noted no exceedences, abnormalities, or vibrations that would indicate any damage to the aircraft. I then called tower and received takeoff clearance. I completed the flight as scheduled and postflt examination revealed no damage to the propeller, engine inlets, main landing gear, or nosewheel. It is in my opinion that this potential incident could have been prevented had I taken the time to clear the windscreen with a soft cloth, soft rubber or plastic scraper, or with deice fluid. In the future, the above procedures will be practiced by this pilot. In the event the above procedures cannot be performed, I will use all available heat to clear the windscreen. However, I will also allow the adequate time needed for the heat to completely defrost the entire windscreen before moving the aircraft in a movement or non movement area.

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Original NASA ASRS Text

Title: A C-208 CARGO PLT SUFFERS A TXWY EXCURSION DURING A NIGHT OP WHEN TAXIING WITH A FROSTED WINDSHIELD AT ICT, KS.

Narrative: I RPTED FOR DUTY, CHKED IN WITH DISPATCH, AND CALLED FOR A WX BRIEFING WITH FSS. I THEN PROCEEDED OUTSIDE AND PERFORMED A PREFLT ACFT CHK. WHILE PERFORMING THE PREFLT, I OBSERVED A THIN LAYER OF FROST (LESS THAN 1/32 INCH THICK) COVERING THE WINDSCREEN AND PORTIONS OF THE ACFT (APPROX 25% OF THE ACFT WAS COVERED WITH FROST). WHILE WEARING A GLOVE, I DRAGGED A FINGER ACROSS THE WINDSCREEN AND EASILY CLRED AN AREA FREE OF FROST, WHILE NOTING ITS THICKNESS. I ELECTED NOT TO DEICE THE ACFT WITH FLUID AND CHOSE TO DEFROST THE WINDSCREEN WITH ENVIRONMENTAL HEAT, AND ELECTRICALLY DEFROST THE HOT PLATE. 5 MINS PRIOR TO LOAD COMPLETION, I CALLED FOR CLRNC AND TURNED ON THE WINDSHIELD ANTI-ICE FOR APPROX 60 SECONDS, CLRING THE HOT PLATE FROM FROST. AFTER LOADING WAS COMPLETE, I SECURED THE CARGO DOOR AND CHOCKS AND WAS READY FOR ENG START. I CALLED GND FOR TAXI AND WAS CLRED FOR TAXI TO RWY 19R. I WAS MARSHALED OUT OF MY SPOT AND BEGAN TAXIING SLOWLY TO RWY 19R WITH ALL AVAILABLE HEAT ON THE WINDSCREEN. THE RTE I CHOSE TO RWY 19R WAS APPROX 800-1000 FT TOTAL TAXI DISTANCE. HOWEVER, WHILE TAXIING, CARGO RAMP LIGHTING AND MY ACFT TAXI LIGHTS WERE CAUSING A GLARE EFFECT ON THE FROSTY WINDSCREEN. THE ACFT LEFT THE HARD SURFACED CARGO AREA. I IMMEDIATELY APPLIED BRAKES AND STOPPED, COMING TO REST IN A GRASSY AREA BTWN THE CARGO RAMP (W OF) AND TXWY D (E OF). I IMMEDIATELY INFORMED GND CTL THAT I WAS IN THE GRASS W OF THE CARGO RAMP. THEY REPLIED 'OK' AND AGAIN ASKED FOR MY POS. I REPLIED WITH MY POS AND ASKED THEM TO HOLD ON SO I COULD ASSESS THE SIT. I THEN OPENED THE PLT'S DOOR AND TURNED ON ALL FORWARD LIGHTING TO SEE THE AREA BETTER. THE GRASS WAS CUT SHORT AND THE GRADE OF THE AREA WAS SUCH THAT I HAD NO CONCERN OF A PROP STRIKE. I INFORMED GND THAT I NEEDED TO MAKE A 180 DEG TURN TO RETURN TO THE CARGO RAMP AREA, AND THEY APPROVED MY REQUEST. HOWEVER, PRIOR TO MOVING THE ACFT, I NOTICED A DRAINAGE GRATE APPROX 10 FT TO THE L OF MY ACFT (S OF MY POS) AND FEARED COLLAPSING THE GRATE IF COMING IN CONTACT WITH IT. I THEN INFORMED GND THAT THE AREA AHEAD OF ME WAS CLR AND ASKED TO TAXI STRAIGHT AHEAD TO TXWY D. THEY APPROVED MY REQUEST, AND I TAXIED SLOWLY AHEAD THROUGH APPROX 50 FT OF GRASS AND RETURNED TO HARD SURFACE ON TXWY D. I CONTINUED TO RWY 19R AND CALLED TWR SHORT OF RWY 19R AND REQUESTED A SHORT DELAY. I THEN PERFORMED AN OVERSPD GOVERNOR CHK AND RECHKED THE PAR UNIT FOR ANY EXCEEDENCES IN ENG PARAMETERS. I NOTED NO EXCEEDENCES, ABNORMALITIES, OR VIBRATIONS THAT WOULD INDICATE ANY DAMAGE TO THE ACFT. I THEN CALLED TWR AND RECEIVED TKOF CLRNC. I COMPLETED THE FLT AS SCHEDULED AND POSTFLT EXAM REVEALED NO DAMAGE TO THE PROP, ENG INLETS, MAIN LNDG GEAR, OR NOSEWHEEL. IT IS IN MY OPINION THAT THIS POTENTIAL INCIDENT COULD HAVE BEEN PREVENTED HAD I TAKEN THE TIME TO CLR THE WINDSCREEN WITH A SOFT CLOTH, SOFT RUBBER OR PLASTIC SCRAPER, OR WITH DEICE FLUID. IN THE FUTURE, THE ABOVE PROCS WILL BE PRACTICED BY THIS PLT. IN THE EVENT THE ABOVE PROCS CANNOT BE PERFORMED, I WILL USE ALL AVAILABLE HEAT TO CLR THE WINDSCREEN. HOWEVER, I WILL ALSO ALLOW THE ADEQUATE TIME NEEDED FOR THE HEAT TO COMPLETELY DEFROST THE ENTIRE WINDSCREEN BEFORE MOVING THE ACFT IN A MOVEMENT OR NON MOVEMENT AREA.

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.