PLTS OF TRAINING FLT RETURNED TO LAND DUE TO A BURNING ODOR IN THE COCKPIT.

Narrative

ACCOMPLISHED NORMAL PREFLT INSPECTION; TAXI; AND TKOF ON ROUTINE TRAINING FLT (FLT REVIEW). SHORTLY AFTER TKOF DURING CRUISE CLB; A STRONG BURNING ODOR WAS NOTICED IN THE CABIN. NO SMOKE WAS OBSERVED BUT ODOR GOT PROGRESSIVELY MORE INTENSE AND CAUSED EYE IRRITATION AND MINOR BREATHING DIFFICULTY. MADE IMMEDIATE DECISION TO LAND. ADVISED ATC OF PRIORITY LNDG AND LANDED UNEVENTFULLY. TAXIED CLR OF RWY AND TXWY TO VACANT RAMP AREA AND SHUT DOWN ACFT ENG. SMOKE WAS THEN OBSERVED COMING OUT OF THE WIND SCREEN DEFROSTER VENTS INSIDE THE CABIN AND OUT THE FRONT END OF THE ENG COWLING. INSPECTION REVEALED A SHOP RAG LEFT INSIDE THE AIR INTAKE FOR THE CABIN HEATING; VENTILATING; AND DEFROSTING SYS. THE RAG HAD GOTTEN HOT AND STARTED TO BURN. THE RAG WAS REMOVED WITH NO APPARENT DAMAGE TO THE ACFT OR CREW. AN ENG OIL CHANGE HAD BEEN ACCOMPLISHED THE DAY BEFORE THIS FLT. APPARENTLY; THE SHOP RAG WAS EITHER PUT INSIDE THE AIR INTAKE FOR SOME REASON; OR WAS SUCKED UP INTO IT FROM INSIDE THE LOWER FRONT ENG COWL DURING FLT. CORRECTIVE ACTIONS: PLTS SHOULD BE ALERT TO CHK FOR THIS TYPE OF THING ANY TIME AN ACFT COMES OUT OF MAINT. MECHS SHOULD BE CAREFUL TO ACCOUNT FOR ALL PARTS; TOOLS; ETC AFTER COMPLETING ANY MAINT ON AN ACFT.