Narrative:

Departed airport on an SVFR clearance; ceiling 300 ft; visibility 1.5 SM. Told to expedite departure for IFR traffic. Flew over river; southeast of airfield; to intercept shoreline and proceed eastbound along shoreline. Noticed that most of city was covered by dark air; resembled a snow shower. But there was no snow; so it must have been smog. Maintained low power and airspeed at 150 ft. Intended to re-evaluate flight upon reaching shoreline. Never made it. Went inadvertent IMC before getting there. Now we were over area surrounded by dwellings; power lines; construction cranes; and storage tanks. Immediately turned toward field but unable to reacquire. Turned southwest and climbed to 300 ft; executed local inadvertent IMC procedure. At approximately 1 SM south of field; gained visual view of surface ice. Descended but unable to see anything ahead. Landed and advised ATC. After about 20 mins; the visibility improved so that I could see the shoreline; utility poles; tanks; etc. I immediately advised ATC and requested clearance. It would take me 1 min to take off and land on the south ramp. ATC unable; had 7 IFR aircraft. After about another 20 mins; the visibility began to deteriorate again; contrary to forecast. I advised ATC and told them I needed to depart now or I might be stuck on the ice. I had to stay at full RPM; and there was no assurance that the WX might improve. They could not assist; so I declared an emergency and took off for the approach end of runway X (runway Y was active). I crossed the utility pole and could not see the runway or nearest hangar (less than 0.2 NM distant). I followed the shrubs until I could see the ramp; then landed and canceled. No hazard to other aircraft. Never declared an emergency before in 28 yrs of aviation experience. Ice; fog; visual restr was intense and set up rapidly.

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Original NASA ASRS Text

Title: A HELI PLT ENCOUNTERS ICE FOG AFTER TKOF. PLT DECLARED AN EMER TO RETURN.

Narrative: DEPARTED ARPT ON AN SVFR CLRNC; CEILING 300 FT; VISIBILITY 1.5 SM. TOLD TO EXPEDITE DEP FOR IFR TFC. FLEW OVER RIVER; SE OF AIRFIELD; TO INTERCEPT SHORELINE AND PROCEED EBOUND ALONG SHORELINE. NOTICED THAT MOST OF CITY WAS COVERED BY DARK AIR; RESEMBLED A SNOW SHOWER. BUT THERE WAS NO SNOW; SO IT MUST HAVE BEEN SMOG. MAINTAINED LOW PWR AND AIRSPD AT 150 FT. INTENDED TO RE-EVALUATE FLT UPON REACHING SHORELINE. NEVER MADE IT. WENT INADVERTENT IMC BEFORE GETTING THERE. NOW WE WERE OVER AREA SURROUNDED BY DWELLINGS; PWR LINES; CONSTRUCTION CRANES; AND STORAGE TANKS. IMMEDIATELY TURNED TOWARD FIELD BUT UNABLE TO REACQUIRE. TURNED SW AND CLBED TO 300 FT; EXECUTED LCL INADVERTENT IMC PROC. AT APPROX 1 SM S OF FIELD; GAINED VISUAL VIEW OF SURFACE ICE. DSNDED BUT UNABLE TO SEE ANYTHING AHEAD. LANDED AND ADVISED ATC. AFTER ABOUT 20 MINS; THE VISIBILITY IMPROVED SO THAT I COULD SEE THE SHORELINE; UTILITY POLES; TANKS; ETC. I IMMEDIATELY ADVISED ATC AND REQUESTED CLRNC. IT WOULD TAKE ME 1 MIN TO TAKE OFF AND LAND ON THE S RAMP. ATC UNABLE; HAD 7 IFR ACFT. AFTER ABOUT ANOTHER 20 MINS; THE VISIBILITY BEGAN TO DETERIORATE AGAIN; CONTRARY TO FORECAST. I ADVISED ATC AND TOLD THEM I NEEDED TO DEPART NOW OR I MIGHT BE STUCK ON THE ICE. I HAD TO STAY AT FULL RPM; AND THERE WAS NO ASSURANCE THAT THE WX MIGHT IMPROVE. THEY COULD NOT ASSIST; SO I DECLARED AN EMER AND TOOK OFF FOR THE APCH END OF RWY X (RWY Y WAS ACTIVE). I CROSSED THE UTILITY POLE AND COULD NOT SEE THE RWY OR NEAREST HANGAR (LESS THAN 0.2 NM DISTANT). I FOLLOWED THE SHRUBS UNTIL I COULD SEE THE RAMP; THEN LANDED AND CANCELED. NO HAZARD TO OTHER ACFT. NEVER DECLARED AN EMER BEFORE IN 28 YRS OF AVIATION EXPERIENCE. ICE; FOG; VISUAL RESTR WAS INTENSE AND SET UP RAPIDLY.

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.