What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) When enroute at 3,500 feet, VFR from bedford, MA. To martha's vineyard, MA. The pilot reported loss of engine power to ATC and advised that he had to make an emergency landing. The a/c made an emergency landing on the westbound lane of Massachusetts turnpike, marlborough, MA. The a/c received substantial damage to the left wing when it impacted a road sign during an emergency landing and also to the propeller when it struck an automobile. There were no injuries. Preliminary inspection of the a/c at the accident scene disclosed that a malfunction of the engine had occurred. Severe engine damage was visible in the number one cylinder area. The information to complete items #29 and #31 is not available. The pilot is presently on a business trip to united kingdom. (.4) the airplane was in a climb, passing 3,500 feet, when the pilot heard a "bang". The engine lost power, and oil began leaking from the engine compartment. The pilot then made a forced landing on the Massachusetts turnpike. During the landing flare, the airplane struck highway reflectors, a sign, and an automobile. Examination of the airplane's Lycoming O-360-A4M engine revealed a breach in the casing, in the vicinity of the number 1 piston. In addition, the number 1 piston connecting rod cap was missing, along with one complete rod bolt, and the manufactured head of the other rod bolt. The fracture surfaces were obliterated, and did not provide any clues of fracture event initiation. Type 74502 connecting rods were used in the overhaul of the engine. Since its certification in November 1974, the O-360-A4M engine had always been manufactured utilizing LW-11750 connecting rods. Predecessor O-360 series engines were manufactured using 74502 connecting rods; however, those rods and their immediate successors were superceded by LW-11750 connecting rods in may 1970. The LW-11750 connecting rod had a larger grip area than the 74502, and utilized a longer rod bolt to secure the connecting rod cap to the connecting rod yoke. There was, however, no evidence that the use of the 74502 connecting rod would have resulted in a rod or rod bolt failure. At the time of the accident, the engine's time since overhaul was 50 hours.
As the FAA filed it
(-23) WHEN ENROUTE AT 3,500 FEET, VFR FROM BEDFORD, MA. TO MARTHA'S VINEYARD, MA. THE PILOT REPORTED LOSS OF ENGINE POWER TO ATC AND ADVISED THAT HE HAD TO MAKE AN EMERGENCY LANDING. THE A/C MADE AN EMERGENCY LANDING ON THE WESTBOUND LANE OF MASSACHUSETTS TURNPIKE, MARLBOROUGH, MA. THE A/C RECEIVED SUBSTANTIAL DAMAGE TO THE LEFT WING WHEN IT IMPACTED A ROAD SIGN DURING AN EMERGENCY LANDING AND ALSO TO THE PROPELLER WHEN IT STRUCK AN AUTOMOBILE. THERE WERE NO INJURIES. PRELIMINARY INSPECTION OF THE A/C AT THE ACCIDENT SCENE DISCLOSED THAT A MALFUNCTION OF THE ENGINE HAD OCCURRED. SEVERE ENGINE DAMAGE WAS VISIBLE IN THE NUMBER ONE CYLINDER AREA. THE INFORMATION TO COMPLETE ITEMS #29 AND #31 IS NOT AVAILABLE. THE PILOT IS PRESENTLY ON A BUSINESS TRIP TO UNITED KINGDOM. (.4) THE AIRPLANE WAS IN A CLIMB, PASSING 3,500 FEET, WHEN THE PILOT HEARD A "BANG". THE ENGINE LOST POWER, AND OIL BEGAN LEAKING FROM THE ENGINE COMPARTMENT. THE PILOT THEN MADE A FORCED LANDING ON THE MASSACHUSETTS TURNPIKE. DURING THE LANDING FLARE, THE AIRPLANE STRUCK HIGHWAY REFLECTORS, A SIGN, AND AN AUTOMOBILE. EXAMINATION OF THE AIRPLANE'S LYCOMING O-360-A4M ENGINE REVEALED A BREACH IN THE CASING, IN THE VICINITY OF THE NUMBER 1 PISTON. IN ADDITION, THE NUMBER 1 PISTON CONNECTING ROD CAP WAS MISSING, ALONG WITH ONE COMPLETE ROD BOLT, AND THE MANUFACTURED HEAD OF THE OTHER ROD BOLT. THE FRACTURE SURFACES WERE OBLITERATED, AND DID NOT PROVIDE ANY CLUES OF FRACTURE EVENT INITIATION. TYPE 74502 CONNECTING RODS WERE USED IN THE OVERHAUL OF THE ENGINE. SINCE ITS CERTIFICATION IN NOVEMBER 1974, THE O-360-A4M ENGINE HAD ALWAYS BEEN MANUFACTURED UTILIZING LW-11750 CONNECTING RODS. PREDECESSOR O-360 SERIES ENGINES WERE MANUFACTURED USING 74502 CONNECTING RODS; HOWEVER, THOSE RODS AND THEIR IMMEDIATE SUCCESSORS WERE SUPERCEDED BY LW-11750 CONNECTING RODS IN MAY 1970. THE LW-11750 CONNECTING ROD HAD A LARGER GRIP AREA THAN THE 74502, AND UTILIZED A LONGER ROD BOLT TO SECURE THE CONNECTING ROD CAP TO THE CONNECTING ROD YOKE. THERE WAS, HOWEVER, NO EVIDENCE THAT THE USE OF THE 74502 CONNECTING ROD WOULD HAVE RESULTED IN A ROD OR ROD BOLT FAILURE. AT THE TIME OF THE ACCIDENT, THE ENGINE'S TIME SINCE OVERHAUL WAS 50 HOURS.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.