Accident Overview
On July 24, 2020, about 1002 Atlantic standard time, a Cessna 177RG, registration N1813Q, was substantially damaged when it nosed over during a forced landing near Salinas, Puerto Rico. The private pilot and flight instructor were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
Flight and Power Loss
The flight departed from Fernando Luis Ribas Dominicci Airport, San Juan, Puerto Rico, about 0852 with full fuel tanks. After conducting airwork near Dorado and performing a touch-and-go landing followed by two full-stop taxi back landings at Mercedita Airport (TJPS), Ponce, the airplane departed TJPS en route to Jose Aponte de la Torre Airport, Ceiba. While climbing to about 1,100 ft mean sea level at an indicated airspeed between 120 and 130 mph, the pilot felt a mild vibration followed by a smooth gradual loss of engine power. He informed the flight instructor, turned on the auxiliary fuel pump, but engine power was not restored. The on-board engine analyzer indicated the engine was cooling rapidly with decreases in exhaust gas temperature (EGT) and cylinder head temperature (CHT) readings.
Forced Landing and Post-Accident Inspection
The pilot identified an open area to his left and informed the instructor of the impending forced landing. He landed with the landing gear and flaps full down; during the landing roll, he retracted the flaps. When the airplane was nearly stopped, it nosed over in soft terrain. After recovery, inspection by a Federal Aviation Administration inspector revealed small amounts of water in samples from each fuel tank, the reservoir tank assembly, and the airframe fuel strainer, with the most water found in the fuel strainer. The tanks were drained and contained about 29 gallons of fuel; the drained fuel did not contain water or contaminants.
Fuel System Examination
The airplane was relocated to San Juan, where examination of the engine fuel system showed the servo fuel injector inlet screen was saturated with ferrous material and exhibited evidence of corrosion and water. The fuel strainer contained foreign debris and water contamination; the internal steel valves of the engine-driven fuel pump exhibited substantial corrosion; and components of the fuel flow divider showed foreign debris and corrosion. Examination of the power train, ignition, air induction, and exhaust systems revealed no evidence of pre-impact failure or malfunction. Testing of the left fuel tank, with the wing positioned about 1.4° (wing dihedral was specified to be 1.5°), showed about 3 ounces of water could not be drained using the sump drain valve.
Fuel Cap Examination
Fuel caps replaced in June 2015 in accordance with supplemental type certificate SA2458CE had seals in good condition. The right cap showed corrosion at the lower portion of the fuel inlet neck assembly and inner inlet spring-loaded plate, and corrosion at the connection point of the fuel level gauge. A bolt and nylon self-locking nut secured the fuel gauge. Operational testing with water flow showed no leakage from the left cap, but leakage from the hardware securing the fuel level gauge to the right cap assembly. According to a fuel cap manufacturer representative, the fuel level gauge was originally secured by a rivet but was later changed to a bolt with Loctite.
Maintenance History
Maintenance records showed no entries between an annual inspection dated July 15, 2016, and the last annual inspection dated November 8, 2019. No mention of sealing of either integral fuel tank between October 8, 2001, and July 10, 2020. The pilot reported that the first flight after the last annual inspection, on February 19, 2020, revealed fuel consumption only from the left tank, later attributed to a blocked fuel vent for the right tank. Beginning February 20, 2020, maintenance addressed water in the fuel tanks, a rough running engine, and a slow right tank sump drain. Maintenance personnel drained about 1/2 gallon of water from both tanks, more from the right. The right tank sump drain was replaced, and slow draining persisted until sealant blocking the sump drain valve boss ports was removed. One mechanic reported the right inlet plate was found without sealant and was sealed; however, the mechanic who did the last annual inspection and the mechanic who removed the right inlet plate both stated it was properly sealed when first inspected. The left inlet plate was not removed by maintenance. The mechanic who signed off the last annual engine inspection reported the servo fuel injector inlet screen was clean with a normal amount of corrosion and no water contamination found at that time; the engine-driven fuel pump was not disassembled.
Engine Data Monitor
Data from the on-board JPI engine monitor showed that about 2 minutes 54 seconds before the end of recorded data, EGT readings for cylinders 1 through 3 began to decrease, while cylinder 4 remained substantially higher. CHT readings for cylinders 1 through 3 also decreased, while cylinder 4 CHT increased. Fuel pressure and fuel flow decreased toward the end of the data.