Accident Overview
On January 18, 2023, at 0903 eastern standard time, a Piper PA-31-350, registration N101MA, was substantially damaged during a runway overrun at Geauga County Airport (7GA) in Middlefield, Ohio. The airline transport pilot and five passengers were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 135 as a non-scheduled passenger flight.
Flight Details
The flight's purpose was to pick up a sixth passenger in Detroit, Michigan, before continuing to Minneapolis, Minnesota. While climbing through approximately 6,000 ft mean sea level (msl) in instrument meteorological conditions (IMC), the pilot observed oil leaking from the right engine nacelle. At about 7,400 ft msl, the pilot noted a loss of right engine power. He secured the engine, declared an emergency, and requested to divert to the closest airport. The air traffic controller vectored the airplane for the RNAV Runway 11 approach at 7GA. The pilot completed the approach and reported touching down in the “first one-third” of the landing runway at an airspeed “about 120 knots with zero flaps.”
Pilot's Decision
The pilot reported to a Federal Aviation Administration (FAA) inspector that he visually acquired the runway about 500 ft above the ground and realized he would not stop the airplane before the departure end of the 3,500-ft-long runway. He chose to continue rather than abort the landing with one engine inoperative and climb back into IMC for another instrument approach.
Runway Overrun
The airplane overran the departure end of the runway, continued through the grass overrun, and impacted a hill and a fence before coming to rest upright about 600 ft beyond the runway end. All three landing gear collapsed, and the airplane sustained substantial damage to the wings and fuselage.
Aircraft Information
According to FAA and maintenance records, the airplane was manufactured in 1977 and powered by two Lycoming TIO-540-J2BD, 350-horsepower engines. The most recent 100-hour inspection was completed on December 12, 2022, at 17,154.5 total aircraft hours, which was 42 hours before the accident. The right engine had accrued 1,662.5 total hours since major overhaul.
Post-Accident Examination
Examination of photographs revealed substantial wrinkling of the fuselage and both wings, as well as torn flight control surfaces. The right engine cowling was opened, revealing cracks in the engine crankcase. The engine was removed and examined at a local aircraft technician's school. A large crack in the crankcase was visible above the No. 5 cylinder, and the crankshaft nose seal was partially displaced. Oil streaks originated from that point and covered the engine case. Oil streaking was also visible on the right engine cowling at the scene.
Crankshaft rotation attempts were unsuccessful. Borescope examination of the No. 5 cylinder revealed damage consistent with detonation. The remaining cylinders did not appear to have the same extensive damage. Attempts to remove the No. 5 cylinder were unsuccessful. Removal of the No. 3 cylinder showed minor detonation signatures in the combustion chamber and on the piston. The No. 5 cylinder was then removed, and the connecting rod was found broken at the large bearing end. Excessive heat and oil starvation signatures were observed at the connecting rod end. The partially-melted piston was removed from the No. 5 cylinder, and a large crater was observed in the combustion chamber from the exhaust valve to the spark plug hole. Attempts to rotate the crankshaft with the two cylinders removed were unsuccessful, likely due to oil starvation and heat damage to the crankshaft. The remaining rocker box covers were removed for visual examination with no discrepancies noted.
Engine Analysis
The spark plugs displayed an “excessively rich mixture” coloration and were sent to Lycoming Engines for analysis in their materials lab. The top spark plug from the No. 5 cylinder displayed a “badly damaged” insulator. A Lycoming Engines representative stated that detonation events are typically associated with a lean fuel mixture, and the damage displayed was likely the result of detonation in the No. 5 cylinder. No source or anomaly that would result in engine detonation was identified.
Pilot's Operating Handbook Guidance
According to the Pilot’s Operating Handbook (POH) for the accident airplane, during a single-engine inoperative approach, the pilot should maintain an airspeed of 116 KIAS or above until landing is assured. Once landing is assured, the pilot should extend the gear and flaps, slowly retard power on the operative engine, and land normally. The airplane's best single-engine rate of climb speed (blue line) was 106 KIAS, and its minimum controllable airspeed with one engine inoperative (Vmca) was 76 KIAS. The maximum speed for full flap extension (40°) was 132 KIAS. The POH also stated that a single-engine go-around should be avoided if at all possible.