Accident Overview
On November 10, 2019, about 0920 eastern standard time, a Mooney M20J, registration N5765H, was substantially damaged during a forced landing in a marsh while on approach to Northeast Florida Regional Airport (SGJ) in St. Augustine, Florida. The airline transport pilot sustained minor injuries and the passenger was seriously injured. The personal flight was conducted under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed Gainesville Regional Airport (GNV) about 0820.
Pilot Account
The pilot reported repositioning the airplane from the facility that performed the annual inspection back to his home airport. While on an extended base leg of the traffic pattern for runway 31, he reduced airspeed from 100 to 95 knots and increased engine power to maintain 95 knots. At that point, the engine began surging for several seconds, followed by a total loss of engine power. The pilot verified the fuel boost pump was on, mixture rich, and fuel selector positioned to a correct tank. He also checked both magnetos with no success. After retracting the landing gear for better glide performance, he realized the airplane would not reach the runway and performed a forced landing to a marsh about 1 mile short of the runway threshold.
Examination Findings
Initial examination by a Federal Aviation Administration (FAA) inspector revealed the airplane came to rest upright, mostly submerged in shallow water. Damage was noted to the right wing and empennage. After recovery, the inspector observed the fuel selector positioned to the right main fuel tank; about 20 gallons of 100-low-lead aviation gasoline was drained from that tank. Water was drained from the left main fuel tank; it had a fuel smell but no observable aviation gasoline.
At a recovery facility, an FAA inspector performed a visual examination of the engine. No obvious defects were found, but corrosion due to submersion in brackish water was present. The fuel injector divider was opened; no fuel was found, but a white crystallized powder similar to salt was observed, consistent with brackish water submersion. Each fuel injector was removed and inspected; all showed evidence of the crystallized powder but no blockages. The top spark plugs and ignition leads had no anomalies. The air filter and air box were also unremarkable.
The engine was subsequently examined by a National Transportation Safety Board investigator. Visual inspection of the engine and propeller revealed no preimpact mechanical malfunctions. The rocker arm covers were removed with no anomalies. Spark plugs were gray in color. A lighted borescope inspection of cylinders and valves showed no anomalies. Hand rotation of the propeller established thumb compression on all cylinders. The magnetos and fuel pump were corroded and could not be tested.
Aircraft Information
The four-seat, low-wing, retractable tricycle landing gear airplane was manufactured in 1984. It was powered by a Lycoming IO-360, 200-hp engine equipped with a three-blade, constant-speed Hartzell propeller. Maintenance records showed the most recent annual inspection was completed on October 30, 2019. At that time, the airframe had accumulated 3,398.4 total hours, and the engine had accumulated 1,610.8 hours since major overhaul. The accident flight was the first flight after the annual, totaling about 1 hour.