N1813QCessna 177RG · 1971

On July 24, 2020, about 1002 Atlantic standard time, a Cessna 177RG, N1813Q, was substantially damaged when it was involved in an accident 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.

The pilot, who was the owner of the airplane, stated that before the flight, he performed a thorough preflight inspection with no fuel contamination noted and an engine run-up with no discrepancies. The flight departed from Fernando Luis Ribas Dominicci Airport, San Juan, Puerto Rico, about 0852 with full fuel tanks and flew west. When near Dorado, the pilot briefly performed airwork, then proceeded to Mercedita Airport (TJPS), Ponce, Puerto Rico. There he performed one touch-and-go landing followed by two full-stop taxi back landings.

After takeoff from TJPS, while en route to Jose Aponte de la Torre Airport, Ceiba, Puerto Rico, the airplane climbed to about 1,100 ft mean sea level. While flying at that altitude, at an indicated airspeed between 120 and 130 mph, in an easterly direction, the pilot "felt this very mild, very mild vibration" followed by a "very smooth gradual loss of engine power." He informed the flight instructor of the loss of engine power and turned on the auxiliary fuel pump but engine power was not restored. The on-board engine analyzer indicated that the engine was cooling rapidly with corresponding decreases of exhaust gas temperature (EGT) and cylinder head temperature (CHT) readings. He noted an open area to his left and informed the flight instructor of the impending forced landing. He landed in the intended area with the landing gear and flaps full down, and during the landing roll, he retracted the flaps. When the airplane was nearly stopped, it nosed over in the soft terrain.

Following recovery of the airplane, inspection by a Federal Aviation Administration inspector revealed small amounts of water in samples taken from each fuel tank, the reservoir tank assembly, and the airframe fuel strainer; the most water was found in the fuel strainer sample. The fuel tanks were then drained and found to contain about 29 gallons of fuel; the drained fuel did not contain water or contaminants.

The airplane was relocated to San Juan, Puerto Rico, where examination of the engine fuel system components revealed the servo fuel injector inlet screen was “saturated” with ferrous material and exhibited evidence of corrosion and water. Further examination of the airframe and engine fuel system components revealed the fuel strainer exhibited foreign debris and water contamination; the internal steel valves of the engine-driven fuel pump exhibited “substantial” corrosion; and the components of the fuel flow divider exhibited foreign debris and corrosion. Examination of the power train, ignition, air induction, and exhaust systems of the engine revealed no evidence of pre-impact failure or malfunction.

Examination of the left and right fuel tanks revealed both fuel cap flanges (also called inlet plates) were sealed to the wing with adhesive similar to PRC/Proseal. Both fuel tank drain valves and drain valve boss ports were inspected with no discrepancies noted. Additionally, during testing of the left fuel tank with the wing positioned about 1.4° (wing dihedral was specified to be 1.5°) about 3 ounces of water could not be drained from the tank using the sump drain valve.

Examination of the fuel caps, which had been replaced in June 2015 in accordance with supplemental type certificate (STC) SA2458CE, revealed the seals of both appeared to be in good condition. Inspection of the right cap revealed evidence of corrosion at the lower portion of the fuel inlet neck assembly and the inner inlet spring-loaded plate. Additionally, corrosion was noted on the right cap at the connection point of the fuel level gauge. A bolt and nylon self-locking nut secured the fuel level gauge to the bottom side of the inlet filler neck. Operational testing of the fuel caps/inlet plates with attached inlet filler necks was performed by attaching and sealing each of them to the lid of a 5-gallon bucket and flowing water over both assemblies. No leakage was noted from the left fuel cap, but leakage was noted from the hardware used to the secure the fuel level gauge to the inlet filler neck/inner plate of the right fuel cap assembly. According to a representative of the fuel cap manufacturer, the fuel level gauge was originally secured to the inlet filler neck and inlet plate by a rivet but was subsequently changed to a bolt with Loctite applied to the threads and nut.

Review of the maintenance records revealed no entries between an annual inspection entry dated July 15, 2016, and the last annual inspection entry dated November 8, 2019. Further review of the airframe maintenance records for entries between October 8, 2001, and July 10, 2020, revealed no mention of sealing of either integral fuel tank.

According to the pilot/owner, the first flight after the last annual inspection was performed on February 19, 2020. During that flight, he noted fuel consumption only from the left fuel tank. The asymmetric fuel burn was later determined to be from a blocked fuel vent for the right fuel tank. Beginning on February 20, 2020, maintenance was performed on the airplane to address owner-reported issues regarding water in the fuel tanks, a rough running engine, and the right fuel tank sump drain being slow to drain.

In response to the pilot/owner’s complaint about water in the fuel tanks, maintenance personnel drained about 1/2 gallon of water from both fuel tanks, with more coming from the right fuel tank. The fuel tank sump drain of the right wing was replaced, but the issue of slow draining still existed; they removed the right inlet plate to inspect the inside of the fuel tank and determined the sump drain valve boss ports were blocked by fuel tank sealant. The sealant was removed from the ports, which corrected the slow-draining issue.

The pilot stated that the mechanic in charge told him that during the fuel system maintenance actions, the fuel cap flange or inlet plate, which is secured to the upper wing skin, was “found without sealant,” and it was subsequently sealed. He added that since then, no water was drained from the wing tank sump drain, reservoir tank, or fuel strainer. The mechanic who did the last annual inspection and the mechanic who removed the right inlet plate both reported the right inlet plate was properly sealed when it was first inspected. The mechanics also reported that there was no time when the right inlet plate was not sealed. According to the mechanics, the left inlet plate was not removed by maintenance personnel.

The mechanic who signed off the last annual inspection of the engine reported he checked the servo fuel injector inlet screen and reported it was clean at that time with a “normal” amount of corrosion. He also reported that during the inspection, he did not find any water contamination of the fuel system, but he added that the airplane at that time was inside the hangar. The engine-driven fuel pump was not disassembled as part of the fuel system inspections.

According to data downloaded from the on-board JPI engine data monitor, about 2 minutes 54 seconds before the end of recorded data, the EGT readings for the Nos. 1 thru 3 cylinders began to decrease, and the EGT reading for the No. 4 cylinder remained substantially higher. While the EGT readings for the Nos. 1 thru 3 cylinders were decreasing, the CHT readings for cylinder Nos. 1 thru 3 also began to decrease, and the CHT reading for the No. 4 cylinder increased. While the majority of the readings for EGT and CHT decreased at the end of the data, the fuel pressure and fuel flow decreased as well.