PROSPECT, OR, USA
N943TA
SIAI-MARCHETTI SF.260B
ABOUT 45 MINUTES INTO THE FLIGHT, THE NUMBER SIX CONNECTING ROD EXPERIENCED A FATIGUE FAILURE, AND CAUSED CATASTROPHIC DAMAGE TO THE ENGINE CRANKCASE. THE FRACTURING OF THE CASE RESULTED IN A LOSS OF OIL, AND THE LOSS OF OIL PRESSURE RESULTED IN A RUNAWAY PROPELLER. THE PILOT THEN EXECUTED A SUCCESSFUL FORCED LANDING, BUT THE AIRCRAFT WAS DAMAGED WHEN IT COLLIDED WITH AN IRRIGATION PIPE AND A FENCE DURING THE LANDING ROLL. THE AIRCRAFT, WHICH IS USED EXTENSIVELY FOR PROFESSIONAL AIR SHOW AEROBATICS, IS POWERED BY AN ENGINE THAT IS CLASSED AS EXPERIMENTAL BECAUSE IT CONTAINS HIGH COMPRESSION PISTONS.
On June 5, 1994, approximately 1915 Pacific daylight time (PDT), a Siai-Marchetti SF.260B, N943TA, collided with irrigation equipment and a fence during a forced landing near Prospect, Oregon. Neither the commercial pilot, nor his passenger were injured, but the airplane sustained substantial damage. The personal pleasure flight, which departed Medford, Oregon, about 1830 PDT, was in visual meteorological conditions at the time of the accident. There was no flight plan filed, and no report of an ELT activation. According to the pilot, about 45 minutes into the flight, there was sudden and violent vibration from the engine. Immediately thereafter, the oil pressure dropped to zero, and the propeller went to maximum rpm, and could not be controlled with the propeller control lever. There were no unobstructed fields available for a forced landing, so he elected to land in a nearby field that was crossed by a fence and an irrigation pipe line. The touchdown was successful, but the aircraft sustained substantial damage when it rolled through the pipe and fence. This aircraft, which is used extensively for professional air show aerobatics, was powered by a Lycoming IO-540-G engine. The engine was classed as experimental because it contained 10.1 to 1 compression ratio pistons, instead of the standard 8.71 to 1 pistons. The engine was sent to Fort Collins, Colorado, where the FAA supervised an inspection teardown by Demars Aero Limited. The FAA report stated that it appeared the number six connecting rod experienced a fatigue failure, which caused catastrophic damage to the engine crankcase. The fracturing of the case released the engine oil, and the loss of oil pressure resulted in a runaway propeller.
THE FRACTURE OF A CONNECTING ROD. FACTORS INCLUDE NO SUITABLE FORCED LANDING SITE, AND A FENCE AND IRRIGATION SYSTEM IN THE FIELD WHERE THE FORCED LANDING TOOK PLACE.
Source: NTSB Aviation Accident Database
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