Narrative:

Preflight inspection, run-up and all mechanical and electrical functions were normal. Departed IFR on runway 35, climbed into overcast toward initial altitude clearance of 2000'. At or about 1000' (shortly after entering clouds), noticed a smell of smoke in cabin. Wife (in back seat) also noted (other 20 passenger were children--too young to notice). Quickly scanned instruments for indication of engine or electrical trouble, or malfunction of anything electrical. Nothing abnormal observed--no smoke, heat nor flame observed, but smell persisted. I immediately requested vectors to return to owd, and declared a distress. Owd tower handed me to bos approach, who cleared me to continue climbing to 2000', and to turn south to set up for localizer 35 approach. I requested a turn and descent inside OM to expedite landing. Bos said he had to take me to OM; I complied. Meanwhile, the smell of smoke dissipated and did not return. The smell was present for about 2 mins total. I shot the localizer and landed with no further problems. Subsequent inspection has revealed no evidence (visibility or odor) of overheating, burning, etc in any wiring, radios, behind the panel, under cowl or elsewhere. A 20 min ground run the next day was normal. I believe the smell may have been an insect or other material inside the heater sleeve. As I applied full power at takeoff, that part of the engine would quickly become very hot; the material would char and smell, but quickly turn to ash and stop smelling. The heater was off throughout the flight, but I suspect that the air vane does not completely seal off to prevent airflow from entering the cabin. I have not yet flown the aircraft, but intend to test it on the ground--and unless further problems arise, test-fly it when VFR WX returns.

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Original NASA ASRS Text

Title: GA SMA SMOKE ODOR IN COCKPIT AFTER TKOF FROM OWD. RETURN LAND.

Narrative: PREFLT INSPECTION, RUN-UP AND ALL MECHANICAL AND ELECTRICAL FUNCTIONS WERE NORMAL. DEPARTED IFR ON RWY 35, CLBED INTO OVCST TOWARD INITIAL ALT CLRNC OF 2000'. AT OR ABOUT 1000' (SHORTLY AFTER ENTERING CLOUDS), NOTICED A SMELL OF SMOKE IN CABIN. WIFE (IN BACK SEAT) ALSO NOTED (OTHER 20 PAX WERE CHILDREN--TOO YOUNG TO NOTICE). QUICKLY SCANNED INSTRUMENTS FOR INDICATION OF ENG OR ELECTRICAL TROUBLE, OR MALFUNCTION OF ANYTHING ELECTRICAL. NOTHING ABNORMAL OBSERVED--NO SMOKE, HEAT NOR FLAME OBSERVED, BUT SMELL PERSISTED. I IMMEDIATELY REQUESTED VECTORS TO RETURN TO OWD, AND DECLARED A DISTRESS. OWD TWR HANDED ME TO BOS APCH, WHO CLRED ME TO CONTINUE CLBING TO 2000', AND TO TURN S TO SET UP FOR LOC 35 APCH. I REQUESTED A TURN AND DSCNT INSIDE OM TO EXPEDITE LNDG. BOS SAID HE HAD TO TAKE ME TO OM; I COMPLIED. MEANWHILE, THE SMELL OF SMOKE DISSIPATED AND DID NOT RETURN. THE SMELL WAS PRESENT FOR ABOUT 2 MINS TOTAL. I SHOT THE LOC AND LANDED WITH NO FURTHER PROBS. SUBSEQUENT INSPECTION HAS REVEALED NO EVIDENCE (VIS OR ODOR) OF OVERHEATING, BURNING, ETC IN ANY WIRING, RADIOS, BEHIND THE PANEL, UNDER COWL OR ELSEWHERE. A 20 MIN GND RUN THE NEXT DAY WAS NORMAL. I BELIEVE THE SMELL MAY HAVE BEEN AN INSECT OR OTHER MATERIAL INSIDE THE HEATER SLEEVE. AS I APPLIED FULL PWR AT TKOF, THAT PART OF THE ENG WOULD QUICKLY BECOME VERY HOT; THE MATERIAL WOULD CHAR AND SMELL, BUT QUICKLY TURN TO ASH AND STOP SMELLING. THE HEATER WAS OFF THROUGHOUT THE FLT, BUT I SUSPECT THAT THE AIR VANE DOES NOT COMPLETELY SEAL OFF TO PREVENT AIRFLOW FROM ENTERING THE CABIN. I HAVE NOT YET FLOWN THE ACFT, BUT INTEND TO TEST IT ON THE GND--AND UNLESS FURTHER PROBS ARISE, TEST-FLY IT WHEN VFR WX RETURNS.

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.