A PIPER PA18 PILOT DESCRIBES THE IN-FLIGHT ENGINE FAILURE HE EXPERIENCED AND LANDING ON A HIGHWAY. ENGINE TEAR-DOWN LATER REVEALED THE ENGINE REAR MAIN DRIVE GEAR WAS FOUND IN PIECES.

Narrative

I WAS ON A PHOTO MISSION WITH A PAX; RETURNING FROM THE LAKE AREA; RUNNING 2350 RPM AND 1/2 CARB HEAT (OUTSIDE AIR TEMP WAS 5 DEGS C) WHEN THE ENG STARTED TO RUN ROUGH AND THE RPM'S DROPPED TO 2100 RPM. THE ENG STABILIZED THERE AND I OPTED TO FLY DIRECTLY TOWARDS HWY; WHICH WAS ABOUT 2 MI AWAY. I ALSO PULLED THE CARB HEAT ON FULL; FIGURING THAT CARB ICING WAS THE CULPRIT. WHEN I WAS ABOUT 1/4 MI FROM THE HWY; THE ENG COMPLETELY STOPPED; NOT EVEN A SPUTTER OR A HICCUP. I NOTICED THAT THE PROP WAS WIND MILLING FREELY; AS IF THERE WAS NO COMPRESSION. I SET UP ON A DOWNWIND FOR THE HWY; CHKED FOR TFC; AND MADE A NON EVENTFUL DEAD STICK LNDG (IS THERE SUCH A THING?). WE DID NOT HAVE ANY CONFLICTS WITH TFC. WE WERE ABLE TO GET THE PLANE OFF THE HWY TIED DOWN WITH STAKES AND STRAPS THAT WE HAD IN THE PLANE. WE PULLED THE PROP THROUGH AND NOTICED A SMALL AMOUNT OF RESISTANCE; BUT NOT NEARLY AS MUCH AS USUAL. ALSO; THE IMPULSE COUPLINGS ON THE MAGNETOS WERE NOT CLOSING WITH THEIR DISTINCT 'CLICK' LIKE USUAL. 2 DAYS LATER; WE WERE ABLE TO GET THE PLANE ON A TRAILER AND MOVE IT VIA THE HWY TO ZZZ. WE REMOVED THE ENG; AND HAD A SHOP START THE TEAR-DOWN OF IT. WE NOTICED THAT THE REAR MAIN DRIVE GEAR WAS IN PIECES; THE CRANKSHAFT WAS FINE; AS WERE ALL THE CYLINDERS. THE LOSS OF THE DRIVE GEAR EXPLAINS THE LOSS OF IGNITION; AND WHY WE HAD NO COMPRESSION (THE CAM IS TURNED BY THAT GEAR). FROM THIS INCIDENT; WHICH IS MY THIRD ENG FAILURE AND FIRST 'UNINTENTIONAL' OFF-FIELD LNDG; I LEARNED SEVERAL THINGS. ONE; I WAS GLAD THAT I HAD GIVEN MYSELF AN OPTION BY STAYING CLOSE TO THE HWY; AS THE TERRAIN IN THAT AREA CAN BE PRETTY UNACCOMMODATING. SECOND; WHILE WE HAD A FEW THINGS WITH US; AND WERE DRESSED RELATIVELY WARM; WE WERE GROSSLY UNPREPARED FOR AN OFF-FIELD LNDG IN THE MOUNTAINS. WE SHOULD HAVE HAD SURVIVAL PACKS WITH US; AS WELL AS MORE CLOTHING.