Narrative:

After completing my walkaround I found a thin loose coating of snow on the leading edge of the wing. It varied a bit due to the 15 KT wind, but it was no more than 5 inches wide in some spots and always less than 1/4 inch in covering. The rest of the entire wing was clean. The tail appeared to have no loose coating whatsoever as observed during my walkaround and examining from standing on top of the jetway. It was a dry, powdery snow which would easily blow off during taxi and takeoff and not adhere to the wing. The temperature was 20 degrees outside and there was no sign of any snow melting and forming ice on the wing. The captain also examined the wings and was able to brush some snow off the leading edge by the fuselage and did not feel any ice and the snow brushed right off. We determined we did not need to get deiced. After completing the taxi checklist, I turned on the wing lights and confirmed that the snow was blowing and falling off the wing. During and after the takeoff roll the wing was completely clean and the aircraft flew normal. The next day I was informed by my captain that a passenger had informed the airline that he saw ice on the wing between the fuselage and the engine. Out of all the possible causes of this I am tending to lean towards that some of this snow on the leading edge may not have blown off during taxi and or takeoff and had melted and frozen during this time due to the engine now being warm. During taxi we maintained a greater than normal distance to the aircraft in front of us, so I do not think that another aircraft's exhaust had melted that portion of the wing's snow causing it to ice up. The possibility of a faulty wing anti-ice valve seems unlikely but possible, and above all I feel our walkaround inspection confirmed nothing more than the loose dry snow which would blow off during taxi and takeoff for a safe, legal departure. Our taxi time after preflight was short and additional buildup minimal, if any, now that the aircraft was moving and the snow was blowing off. I now feel that you can never really be sure that absolutely no ice exists under any of the snow or that every bit of snow will blow off during taxi and takeoff. The thin loose coating of snow that existed on the leading edge that evening no longer meets my requirements for what actually is a 'thin loose coating of snow,' and for future flts I plan to de-ice anytime there is a thin coating of loose dry snow, regardless of whether or not I feel it may come off during taxi and takeoff.

Google
 

Original NASA ASRS Text

Title: PAX RPTED AN ACR MLG MADE A TKOF AT CLE AT NIGHT WITH ICE ON THE WING.

Narrative: AFTER COMPLETING MY WALKAROUND I FOUND A THIN LOOSE COATING OF SNOW ON THE LEADING EDGE OF THE WING. IT VARIED A BIT DUE TO THE 15 KT WIND, BUT IT WAS NO MORE THAN 5 INCHES WIDE IN SOME SPOTS AND ALWAYS LESS THAN 1/4 INCH IN COVERING. THE REST OF THE ENTIRE WING WAS CLEAN. THE TAIL APPEARED TO HAVE NO LOOSE COATING WHATSOEVER AS OBSERVED DURING MY WALKAROUND AND EXAMINING FROM STANDING ON TOP OF THE JETWAY. IT WAS A DRY, POWDERY SNOW WHICH WOULD EASILY BLOW OFF DURING TAXI AND TKOF AND NOT ADHERE TO THE WING. THE TEMP WAS 20 DEGS OUTSIDE AND THERE WAS NO SIGN OF ANY SNOW MELTING AND FORMING ICE ON THE WING. THE CAPT ALSO EXAMINED THE WINGS AND WAS ABLE TO BRUSH SOME SNOW OFF THE LEADING EDGE BY THE FUSELAGE AND DID NOT FEEL ANY ICE AND THE SNOW BRUSHED RIGHT OFF. WE DETERMINED WE DID NOT NEED TO GET DEICED. AFTER COMPLETING THE TAXI CHKLIST, I TURNED ON THE WING LIGHTS AND CONFIRMED THAT THE SNOW WAS BLOWING AND FALLING OFF THE WING. DURING AND AFTER THE TKOF ROLL THE WING WAS COMPLETELY CLEAN AND THE ACFT FLEW NORMAL. THE NEXT DAY I WAS INFORMED BY MY CAPT THAT A PAX HAD INFORMED THE AIRLINE THAT HE SAW ICE ON THE WING BTWN THE FUSELAGE AND THE ENG. OUT OF ALL THE POSSIBLE CAUSES OF THIS I AM TENDING TO LEAN TOWARDS THAT SOME OF THIS SNOW ON THE LEADING EDGE MAY NOT HAVE BLOWN OFF DURING TAXI AND OR TKOF AND HAD MELTED AND FROZEN DURING THIS TIME DUE TO THE ENG NOW BEING WARM. DURING TAXI WE MAINTAINED A GREATER THAN NORMAL DISTANCE TO THE ACFT IN FRONT OF US, SO I DO NOT THINK THAT ANOTHER ACFT'S EXHAUST HAD MELTED THAT PORTION OF THE WING'S SNOW CAUSING IT TO ICE UP. THE POSSIBILITY OF A FAULTY WING ANTI-ICE VALVE SEEMS UNLIKELY BUT POSSIBLE, AND ABOVE ALL I FEEL OUR WALKAROUND INSPECTION CONFIRMED NOTHING MORE THAN THE LOOSE DRY SNOW WHICH WOULD BLOW OFF DURING TAXI AND TKOF FOR A SAFE, LEGAL DEP. OUR TAXI TIME AFTER PREFLT WAS SHORT AND ADDITIONAL BUILDUP MINIMAL, IF ANY, NOW THAT THE ACFT WAS MOVING AND THE SNOW WAS BLOWING OFF. I NOW FEEL THAT YOU CAN NEVER REALLY BE SURE THAT ABSOLUTELY NO ICE EXISTS UNDER ANY OF THE SNOW OR THAT EVERY BIT OF SNOW WILL BLOW OFF DURING TAXI AND TKOF. THE THIN LOOSE COATING OF SNOW THAT EXISTED ON THE LEADING EDGE THAT EVENING NO LONGER MEETS MY REQUIREMENTS FOR WHAT ACTUALLY IS A 'THIN LOOSE COATING OF SNOW,' AND FOR FUTURE FLTS I PLAN TO DE-ICE ANYTIME THERE IS A THIN COATING OF LOOSE DRY SNOW, REGARDLESS OF WHETHER OR NOT I FEEL IT MAY COME OFF DURING TAXI AND TKOF.

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.