PLT OF A STINSON; TOWING A BANNER; DROPPED HIS BANNER AND RETURNED TO DEP ARPT DUE TO SMOKE COMING FROM THE ENG OR PROP AND OIL COVERING THE WINDSHIELD.

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MY WKEND JOB IS TOWING BANNERS. THE STINSON I FLY HAS A 190 HP LYCOMING O435 AND A VARIABLE PITCH HARTZELL PROP. OIL CAPACITY IS 12 QUARTS. CHAIN OF EVENTS: I HAD JUST PICKED UP A 30 FT BY 80 FT PANEL BANNER AND WAS ABOUT 5 MI NW OF LGB ARPT. MY ALT WAS APPROX 1000 FT WHEN I CAUGHT A FAINT WHIFF OF SOMETHING BURNING. THE SMELL WAS PARTICULARLY DIFFICULT TO RECOGNIZE; SO I MOVED THE FRESH AIR VENT (LOCATED ON THE PAX SIDE WINDOW) TO DRAW AIR FROM OUTSIDE THE ACFT. I REASONED THAT THIS MIGHT AID IN TROUBLESHOOTING IF THE SMELL WAS INSIDE OR OUTSIDE THE ACFT. AS SOON AS I MOVED THE VENT; THE SMELL INTENSIFIED AND AS I LOOKED FORWARD I NOTICED WHAT LOOKED LIKE THE BEGINNING OF AN ENG FIRE. ELAPSED TIME APPROX 10 SECONDS. I IMMEDIATELY TURNED TOWARDS THE ARPT (LGB) AND MADE A RADIO CALL TO ANNOUNCE I WAS TURNING AROUND FOR A LNDG. TWR RESPONDED SAYING THAT I WAS UNREADABLE. TWR THEN CLRED ME FOR A FREQ CHANGE; PROBABLY ASSUMING THAT I WANTED ONE. BY THIS TIME; LARGE CLUMPS OF SLUDGE WERE STICKING TO THE WINDSCREEN; AND THERE WAS A GREAT DEAL OF SMOKE COMING FROM THE COWL AND BEGINNING TO FILL THE COCKPIT. AS I LOOKED FOR A POSSIBLE LNDG SITE; I RADIOED THE TWR DECLARING AN EMER. AS I WAS MAKING THE CALL TO TWR; MY WINDSHIELD BECAME COVERED WITH OIL AND THE COCKPIT FILLED WITH SMOKE. TWR RETURNED MY XMISSION SAYING I WAS UNREADABLE. I FIGURED THAT MAYBE OIL WAS COVERING THE ANTENNA. I THEN SQUAWKED 7700. MY VISIBILITY HAD BECOME LIMITED TO A PORTION OF THE SIDE WINDOWS AND DOWN OUT OF MY NOW OPENED PLT SIDE DOOR. I MOVED THE FRESH AIR VENT TO SUCTION THE SMOKE OUT OF THE COCKPIT. AS I CONTINUED TOWARDS THE ARPT; I REALIZED THAT I WOULD NOT BE ABLE TO MAKE IT WITH THE BANNER ATTACHED. AN OFF-FIELD LNDG WAS OUT OF THE QUESTION DUE TO MY VERY LIMITED VISIBILITY. THE ENG CONTINUED TO RUN ALTHOUGH MY MANIFOLD PRESSURE; RPM'S; AND OIL PRESSURE WERE RAPIDLY DECREASING. I MANEUVERED THE ACFT OVER AN INDUSTRIAL COMPLEX JUST TO MY L AND RELEASED THE BANNER. MY INTENTIONS WERE TO DROP THE BANNER IN THE INDUSTRIAL AREA; AND I ACCOUNTED FOR POSSIBLE WIND DRIFT. IT IS MY KNOWLEDGE THAT THE BANNER WAS RECOVERED 2 DAYS AFTER THE INCIDENT. UPON RELEASING THE BANNER; I BECAME HOPEFUL OF REACHING THE ARPT SAFELY. I'M NOT EXACTLY SURE OF MY ALT AT THAT POINT; BUT IT WAS BELOW 800 FT. I BELIEVE I RADIOED LGB ONE MORE TIME TO ANNOUNCE MY INTENTIONS OF LNDG ON RWY 16L (INACTIVE AT THE TIME). I SHUT DOWN AND SECURED THE ENG SHORTLY AFTER DROPPING THE BANNER AND COMMENCED A PWR-OFF GLIDE TO RWY 16L. IN PREPARATION FOR THE LNDG; I ALSO SHUT OFF THE MASTER SWITCH AND TIGHTENED MY SEATBELTS REAL TIGHT. AS I CROSSED OVER RWY 25R (ACTIVE AT THE TIME); I NOTICED AN ACFT DEPARTING BELOW ME. MY ALT WAS ABOUT 100-150 FT; BUT I DON'T BELIEVE THERE WAS A THREAT OF COLLISION. MY FORWARD VISIBILITY WAS STILL COMPLETELY OBSCURED BY THE OIL SOAKED WINDSCREEN. LUCKILY; THE WIND WAS BLOWING RIGHT DOWN THE RWY (ANOTHER REASON FOR LNDG ON RWY 16L). LOOKING OUT THE SIDE WINDOW; I SAFELY BROUGHT THE ACFT TO REST ON THE RWY BTWN ACTIVE RWYS. I DID NOT HAVE ENOUGH SPD TO EXIT THE RWY. WHEN THE ACFT STOPPED; I UNBUCKLED; GRABBED MY LUNCH; AND RAN CLR OF THE PLANE. THE EMER CREWS ARRIVED A FEW MINS LATER. WHAT HAPPENED? OIL WAS FOUND FROM THE PROP AREA RUNNING ALL THE WAY BACK TO THE TAIL FEATHERS. FURTHER INSPECTION REVEALED A SEVERELY DAMAGED JACK PLATE ON THE PROP. APPARENTLY; THE BEARINGS IN THE SPINNER PLATE HAD SOMEHOW BROKEN. WHEN THIS HAPPENED; THE SPINNER PLATE GROUND THROUGH THE JACK PLATE LOCATED BEHIND IT. THIS GENERATED AN INCREDIBLE AMOUNT OF HEAT WHICH SUBSEQUENTLY BURNED THE OIL BLADDER LOCATED BEHIND THE JACK PLATE. I DON'T KNOW WHY THIS HAPPENED; AND THERE WAS NOTHING NOTICEABLE DURING MY PREFLT.