What happened
On December 29, 2021, a Cessna 207 operated by ExecAir of Naples was performing a return flight from The Florida Keys Marathon International Airport (MTH) to Naples Municipal Airport (APF). While cruising at approximately 3,800 feet mean sea level over the water, the aircraft began to shake and lose power. Although the pilot noted that engine instruments and oil pressure appeared normal, adjusting the throttle, propeller, and mixture controls did not restore power.
The pilot established best glide airspeed, issued a mayday call, and turned back toward MTH. During the descent, oil was observed leaking from the engine cowling. Realizing the aircraft could not reach land, the pilot performed a forced ditching in the Florida Bay. The aircraft, registration N1596U, remained upright after the impact. The pilot sustained one serious injury, and the two passengers sustained two minor injuries. All occupants successfully egressed the aircraft and were rescued by a passing recreational vessel.
The investigation
NTSB investigators examined the engine and found a large fracture hole and loose internal components at the top aft portion of the engine case near the No. 2 cylinder. While the engine showed little impact damage, saltwater corrosion was present due to the aircraft being submerged for several days.
Detailed examination revealed that the No. 2 cylinder connecting rod crankshaft end was heavily fragmented. The crankshaft journal for the No. 2 connecting rod showed evidence of wear, heat transfer, and deformation of the oil transfer hole. Forensic examination of the No. 2 connecting rod assembly and bearings by the NTSB Materials Laboratory showed the rod end was blackened from high heat and the bearing was thinned, fractured, and severely deformed. The No. 3 connecting rod bearings also showed signs of displaced and smeared babbitt material.
Maintenance records indicated that the No. 2 and No. 6 cylinders had been replaced approximately one month prior to the accident due to ring blow-by and a fractured exhaust stud, respectively. Additionally, an overhauled propeller and governor had been reinstalled 2.2 hours before the accident.