Narrative:

During an IFR cross country from luk to mcn, we encountered light icing about 20 NM nnw from the loz VOR. The wings looked just slightly frosty, almost as though someone had been breathing on the wings. There even appeared to be a slight 'shadowing' of the wings. We exercised good CRM and immediately decided to divert to the nearest airport, which thankfully had a VOR approach. However, while we descended from the MEA for the instrument approach, we picked up moderate mixed icing. The temperature at the MEA (5000 ft) was 30 degrees F. I assumed that a descent of 3000 ft for the approach would prevent additional ice from forming. Was I in for an unpleasant surprise! We quickly picked up between 1/2 - 3/4 of an inch on the entire airplane, and the temperature gauge never moved from 30 degrees F during the entire approach. I am writing this form to admit some mistakes I made and reveal some things I learned. I was wrong to think that I could fly through an area forecasted to have light to moderate rime icing in the clouds. I assumed that because layers were reported that I would easily find an altitude that would keep me out of the clouds. I put myself in a situation where I felt I would have to declare an emergency before it was too late. I could have never imagined how quickly the airplane went from 'feeling like' a C172 to 'feeling like' a heavy B747. We were a very heavy C172. We took off at maximum gross weight, 3 passenger and full fuel in a C172 with extended fuel tanks. We had a GPS on board that really allowed me to see the affect the ice had on our airplane. As we picked up more and more ice, I noticed that the ground speed indicated on the GPS continued to decrease. Another thing I learned is that it's really easy to spot ice accumulation on the black tires. I will never fly in known or forecasted icing conditions ever again.

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Original NASA ASRS Text

Title: A C172 ENCOUNTERED FORECAST ICING CONDITIONS NEAR LOZ.

Narrative: DURING AN IFR XCOUNTRY FROM LUK TO MCN, WE ENCOUNTERED LIGHT ICING ABOUT 20 NM NNW FROM THE LOZ VOR. THE WINGS LOOKED JUST SLIGHTLY FROSTY, ALMOST AS THOUGH SOMEONE HAD BEEN BREATHING ON THE WINGS. THERE EVEN APPEARED TO BE A SLIGHT 'SHADOWING' OF THE WINGS. WE EXERCISED GOOD CRM AND IMMEDIATELY DECIDED TO DIVERT TO THE NEAREST ARPT, WHICH THANKFULLY HAD A VOR APCH. HOWEVER, WHILE WE DSNDED FROM THE MEA FOR THE INST APCH, WE PICKED UP MODERATE MIXED ICING. THE TEMP AT THE MEA (5000 FT) WAS 30 DEGS F. I ASSUMED THAT A DSCNT OF 3000 FT FOR THE APCH WOULD PREVENT ADDITIONAL ICE FROM FORMING. WAS I IN FOR AN UNPLEASANT SURPRISE! WE QUICKLY PICKED UP BTWN 1/2 - 3/4 OF AN INCH ON THE ENTIRE AIRPLANE, AND THE TEMP GAUGE NEVER MOVED FROM 30 DEGS F DURING THE ENTIRE APCH. I AM WRITING THIS FORM TO ADMIT SOME MISTAKES I MADE AND REVEAL SOME THINGS I LEARNED. I WAS WRONG TO THINK THAT I COULD FLY THROUGH AN AREA FORECASTED TO HAVE LIGHT TO MODERATE RIME ICING IN THE CLOUDS. I ASSUMED THAT BECAUSE LAYERS WERE RPTED THAT I WOULD EASILY FIND AN ALT THAT WOULD KEEP ME OUT OF THE CLOUDS. I PUT MYSELF IN A SIT WHERE I FELT I WOULD HAVE TO DECLARE AN EMER BEFORE IT WAS TOO LATE. I COULD HAVE NEVER IMAGINED HOW QUICKLY THE AIRPLANE WENT FROM 'FEELING LIKE' A C172 TO 'FEELING LIKE' A HVY B747. WE WERE A VERY HVY C172. WE TOOK OFF AT MAX GROSS WT, 3 PAX AND FULL FUEL IN A C172 WITH EXTENDED FUEL TANKS. WE HAD A GPS ON BOARD THAT REALLY ALLOWED ME TO SEE THE AFFECT THE ICE HAD ON OUR AIRPLANE. AS WE PICKED UP MORE AND MORE ICE, I NOTICED THAT THE GND SPD INDICATED ON THE GPS CONTINUED TO DECREASE. ANOTHER THING I LEARNED IS THAT IT'S REALLY EASY TO SPOT ICE ACCUMULATION ON THE BLACK TIRES. I WILL NEVER FLY IN KNOWN OR FORECASTED ICING CONDITIONS EVER AGAIN.

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.