Narrative:

Departed ZZZ for direct VFR flight to ZZZ1. Received FSS briefing indicating flight could be accomplished VFR. Airmets were in effect for moderate turbulence and icing; but there was no plan to enter IMC and briefing indicated this would not be necessary. A VFR flight plan was filed and opened prior to departure. Flight following was also established immediately after departure. About 120 mi from destination; layers of scattered clouds were observed ahead of flight path. Flight watch was contacted for an updated briefing. No indication of problem continuing VFR flight to destination was received. Despite this; pilot requested a pop-up IFR clearance in the event VFR cloud clearance was not possible. This was easy to do as the pilot had been in constant communication with ATC throughout the flight while receiving VFR advisories. IFR clearance was received for 6000 ft and direct to ZZZ1. Pilot maintained this altitude while coming close to clouds but rarely entering IMC and then only for brief periods of time. As the pilot got closer to the destination; IMC became more frequent and duration of episodes extended. Aware of airmet for icing; pilot was attentive to any signs of accumulation and was not willing to maintain IMC flight for anything other than brief periods. Light rime ice accumulation began and pilot immediately requested and received a lower altitude (4000 ft). Still in IMC at 4000 ft; pilot requested a lower altitude; which was denied by ATC due to minimum IFR altitude requirements in the area. Pilot was informed this deviation could only be accomplished by declaring an emergency -- which was done. Pilot had current VFR charts which verified adequate terrain and obstacle clearance for desired altitude based on mef's for the remainder of the flight. Pilot options included canceling IFR; declaring emergency and maintaining IFR flight plan; diverting to an alternate; or turning around. Course of action was chosen (declaration of emergency) in order to maintain as high an altitude as possible (ie; fly just below cloud deck) and for benefit of uncertain meteorological conditions between present position and destination. Alternate was not chosen as flight conditions at lower altitude; albeit not within ATC clearance capabilities; enabled ice free flight at safe altitude. Pilot did not turn around as flight characteristics under icing conditions are not known or reliable (increased stall speed; etc). Maneuvering flight in these conditions; along with staying in the icing conditions; was not advisable. Even in the case of flying to an alternate or turning around; the pilot would still have had to declare an emergency in order to get to a lower altitude to get out of icing conditions prior to these actions. Remainder of flight was accomplished initially maintaining 3300 ft and closer to destination at 3500 ft with no additional issues or ATC assistance outside of normal IFR requirements (handoffs; vectors for ILS approach; etc). Flight terminated with a visual approach with a ceiling of approximately 3500 ft within the vicinity of ZZZ1. In summary; pilot received FSS briefing and flight watch update en route and neither indicated VFR flight was not advisable or that IMC were present at the departure; along the route of flight; or at destination. Pilot filed IFR during flight as a precautionary measure; which proved necessary as VFR cloud clearance requirements were not able to be maintained. When entering somewhat sustained IMC; pilot was not comfortable with maintaining flight in IMC based on the existing airmet and requested an altitude too low for ATC IFR requirements. Pilot declared an emergency to avoid an existing hazard and to enable safe termination of the flight.

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Original NASA ASRS Text

Title: A GA PILOT ENCOUNTERED WEATHER AND INFLIGHT ICING; DECLARED AN EMERGENCY AND DESCENDED OUT OF ICING CONDITIONS.

Narrative: DEPARTED ZZZ FOR DIRECT VFR FLT TO ZZZ1. RECEIVED FSS BRIEFING INDICATING FLT COULD BE ACCOMPLISHED VFR. AIRMETS WERE IN EFFECT FOR MODERATE TURB AND ICING; BUT THERE WAS NO PLAN TO ENTER IMC AND BRIEFING INDICATED THIS WOULD NOT BE NECESSARY. A VFR FLT PLAN WAS FILED AND OPENED PRIOR TO DEP. FLT FOLLOWING WAS ALSO ESTABLISHED IMMEDIATELY AFTER DEP. ABOUT 120 MI FROM DEST; LAYERS OF SCATTERED CLOUDS WERE OBSERVED AHEAD OF FLT PATH. FLT WATCH WAS CONTACTED FOR AN UPDATED BRIEFING. NO INDICATION OF PROB CONTINUING VFR FLT TO DEST WAS RECEIVED. DESPITE THIS; PLT REQUESTED A POP-UP IFR CLRNC IN THE EVENT VFR CLOUD CLRNC WAS NOT POSSIBLE. THIS WAS EASY TO DO AS THE PLT HAD BEEN IN CONSTANT COM WITH ATC THROUGHOUT THE FLT WHILE RECEIVING VFR ADVISORIES. IFR CLRNC WAS RECEIVED FOR 6000 FT AND DIRECT TO ZZZ1. PLT MAINTAINED THIS ALT WHILE COMING CLOSE TO CLOUDS BUT RARELY ENTERING IMC AND THEN ONLY FOR BRIEF PERIODS OF TIME. AS THE PLT GOT CLOSER TO THE DEST; IMC BECAME MORE FREQUENT AND DURATION OF EPISODES EXTENDED. AWARE OF AIRMET FOR ICING; PLT WAS ATTENTIVE TO ANY SIGNS OF ACCUMULATION AND WAS NOT WILLING TO MAINTAIN IMC FLT FOR ANYTHING OTHER THAN BRIEF PERIODS. LIGHT RIME ICE ACCUMULATION BEGAN AND PLT IMMEDIATELY REQUESTED AND RECEIVED A LOWER ALT (4000 FT). STILL IN IMC AT 4000 FT; PLT REQUESTED A LOWER ALT; WHICH WAS DENIED BY ATC DUE TO MINIMUM IFR ALT REQUIREMENTS IN THE AREA. PLT WAS INFORMED THIS DEV COULD ONLY BE ACCOMPLISHED BY DECLARING AN EMER -- WHICH WAS DONE. PLT HAD CURRENT VFR CHARTS WHICH VERIFIED ADEQUATE TERRAIN AND OBSTACLE CLRNC FOR DESIRED ALT BASED ON MEF'S FOR THE REMAINDER OF THE FLT. PLT OPTIONS INCLUDED CANCELING IFR; DECLARING EMER AND MAINTAINING IFR FLT PLAN; DIVERTING TO AN ALTERNATE; OR TURNING AROUND. COURSE OF ACTION WAS CHOSEN (DECLARATION OF EMER) IN ORDER TO MAINTAIN AS HIGH AN ALT AS POSSIBLE (IE; FLY JUST BELOW CLOUD DECK) AND FOR BENEFIT OF UNCERTAIN METEOROLOGICAL CONDITIONS BTWN PRESENT POS AND DEST. ALTERNATE WAS NOT CHOSEN AS FLT CONDITIONS AT LOWER ALT; ALBEIT NOT WITHIN ATC CLRNC CAPABILITIES; ENABLED ICE FREE FLT AT SAFE ALT. PLT DID NOT TURN AROUND AS FLT CHARACTERISTICS UNDER ICING CONDITIONS ARE NOT KNOWN OR RELIABLE (INCREASED STALL SPD; ETC). MANEUVERING FLT IN THESE CONDITIONS; ALONG WITH STAYING IN THE ICING CONDITIONS; WAS NOT ADVISABLE. EVEN IN THE CASE OF FLYING TO AN ALTERNATE OR TURNING AROUND; THE PLT WOULD STILL HAVE HAD TO DECLARE AN EMER IN ORDER TO GET TO A LOWER ALT TO GET OUT OF ICING CONDITIONS PRIOR TO THESE ACTIONS. REMAINDER OF FLT WAS ACCOMPLISHED INITIALLY MAINTAINING 3300 FT AND CLOSER TO DEST AT 3500 FT WITH NO ADDITIONAL ISSUES OR ATC ASSISTANCE OUTSIDE OF NORMAL IFR REQUIREMENTS (HDOFS; VECTORS FOR ILS APCH; ETC). FLT TERMINATED WITH A VISUAL APCH WITH A CEILING OF APPROX 3500 FT WITHIN THE VICINITY OF ZZZ1. IN SUMMARY; PLT RECEIVED FSS BRIEFING AND FLT WATCH UPDATE ENRTE AND NEITHER INDICATED VFR FLT WAS NOT ADVISABLE OR THAT IMC WERE PRESENT AT THE DEP; ALONG THE RTE OF FLT; OR AT DEST. PLT FILED IFR DURING FLT AS A PRECAUTIONARY MEASURE; WHICH PROVED NECESSARY AS VFR CLOUD CLRNC REQUIREMENTS WERE NOT ABLE TO BE MAINTAINED. WHEN ENTERING SOMEWHAT SUSTAINED IMC; PLT WAS NOT COMFORTABLE WITH MAINTAINING FLT IN IMC BASED ON THE EXISTING AIRMET AND REQUESTED AN ALT TOO LOW FOR ATC IFR REQUIREMENTS. PLT DECLARED AN EMER TO AVOID AN EXISTING HAZARD AND TO ENABLE SAFE TERMINATION OF THE FLT.

Data retrieved from NASA's ASRS site as of May 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.