Narrative:

Had flown flight xx to fai at XA45 am. Saw no evidence of volcanic ash plume. Pilot reports prior to departure and after departure indicated no ash. Return flight uneventful--no ash evident was on ground in anc approximately 1 hour. Flight xy from dead horse reported another volcanic eruption from mt redoubt about 10 mins before our departure talked to this incoming flight crew about best way to avoid by wide margin the volcanic ash. They indicated out the northwest, the same way they were coming in. I questioned this due to winds aloft from southwest, which would have pushed plume toward anc. They said eruption appeared vertical. Plume appeared to have no direction. I asked how far away it appeared. They said hard to determine. Mt redoubt is 85 NM from anc on 220 degree right. Departed anc mins after this PIREP. Contacted approach, told them our intentions. They said they could vector us around south of kenai. Told them we had very recent PIREP of area clear out northwest. At 12000' while IMC the clouds appeared to lighten up,indicating we were getting on top. At 15000' it got definitely darker. Asked for heading further east. Determined at FL180 that we had probably encountered ash, even though no sulphur smell. Asked for lower, decided to return to anc due to safety consideration. On arrival found windshield and leading edges slightly pitted. On further consideration, I feel due to plumes rate of travel of 60 KTS and our departure time after eruption of about 10 mins, that we could have been nowhere near the most recent eruption's ash. Must have inadvertently entered small layer from previous day's eruption. This layer was in no way apparent to us in our previous flight or company's flight. Conclusion: do not fly in IMC when volcanic ash (no matter how long it's been from that eruption) is even the least bit possible. I thought I had planned for all possibilities--apparently not.

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Original NASA ASRS Text

Title: INFLT ENCOUNTER WITH VOLCANIC ASH IN ALASKA.

Narrative: HAD FLOWN FLT XX TO FAI AT XA45 AM. SAW NO EVIDENCE OF VOLCANIC ASH PLUME. PLT RPTS PRIOR TO DEP AND AFTER DEP INDICATED NO ASH. RETURN FLT UNEVENTFUL--NO ASH EVIDENT WAS ON GND IN ANC APPROX 1 HR. FLT XY FROM DEAD HORSE RPTED ANOTHER VOLCANIC ERUPTION FROM MT REDOUBT ABOUT 10 MINS BEFORE OUR DEP TALKED TO THIS INCOMING FLT CREW ABOUT BEST WAY TO AVOID BY WIDE MARGIN THE VOLCANIC ASH. THEY INDICATED OUT THE NW, THE SAME WAY THEY WERE COMING IN. I QUESTIONED THIS DUE TO WINDS ALOFT FROM SW, WHICH WOULD HAVE PUSHED PLUME TOWARD ANC. THEY SAID ERUPTION APPEARED VERT. PLUME APPEARED TO HAVE NO DIRECTION. I ASKED HOW FAR AWAY IT APPEARED. THEY SAID HARD TO DETERMINE. MT REDOUBT IS 85 NM FROM ANC ON 220 DEG R. DEPARTED ANC MINS AFTER THIS PIREP. CONTACTED APCH, TOLD THEM OUR INTENTIONS. THEY SAID THEY COULD VECTOR US AROUND S OF KENAI. TOLD THEM WE HAD VERY RECENT PIREP OF AREA CLR OUT NW. AT 12000' WHILE IMC THE CLOUDS APPEARED TO LIGHTEN UP,INDICATING WE WERE GETTING ON TOP. AT 15000' IT GOT DEFINITELY DARKER. ASKED FOR HDG FURTHER E. DETERMINED AT FL180 THAT WE HAD PROBABLY ENCOUNTERED ASH, EVEN THOUGH NO SULPHUR SMELL. ASKED FOR LOWER, DECIDED TO RETURN TO ANC DUE TO SAFETY CONSIDERATION. ON ARR FOUND WINDSHIELD AND LEADING EDGES SLIGHTLY PITTED. ON FURTHER CONSIDERATION, I FEEL DUE TO PLUMES RATE OF TRAVEL OF 60 KTS AND OUR DEP TIME AFTER ERUPTION OF ABOUT 10 MINS, THAT WE COULD HAVE BEEN NOWHERE NEAR THE MOST RECENT ERUPTION'S ASH. MUST HAVE INADVERTENTLY ENTERED SMALL LAYER FROM PREVIOUS DAY'S ERUPTION. THIS LAYER WAS IN NO WAY APPARENT TO US IN OUR PREVIOUS FLT OR COMPANY'S FLT. CONCLUSION: DO NOT FLY IN IMC WHEN VOLCANIC ASH (NO MATTER HOW LONG IT'S BEEN FROM THAT ERUPTION) IS EVEN THE LEAST BIT POSSIBLE. I THOUGHT I HAD PLANNED FOR ALL POSSIBILITIES--APPARENTLY NOT.

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