What happened
On January 19, 2023, at approximately 0800 Pacific standard time, a Piper PA-28R-200, registration N5lar55, was conducting a Part 91 instructional flight near Carlsbad, California. The crew, consisting of a flight instructor, a student pilot, and a passenger, had planned a flight to Santa Ana to accumulate flight time.
After climbing to 2,500 feet mean sea level (msl) and turning to a northerly heading, the instructor noticed the oil pressure gauge dropping below zero psi, though oil temperature remained normal. The instructor notified air traffic control (ATC) of their intention to divert to a nearby airport. As the aircraft reached 3,200 feet msl, the propeller transitioned to maximum rpm, and smoke began entering the cockpit through the defrosters accompanied by an oil smell. Following a loud noise from the engine compartment, the propeller stopped turning and smoke emerged from the cowling.
The crew decided to perform a water landing. The student pilot flew the aircraft to the surface, touching down approximately 50 yards from the shoreline with the landing gear retracted. All occupants were not injured.
The investigation
Post-accident examination of the N57355 revealed significant structural damage, including a fractured left wing at mid-span and buckling of the fuselage aft of the wings. The engine remained attached to its mounts but was contaminated by salt water and rock debris.
A breach was discovered in the engine case between the pushrod tubes of the No. 2 cylinder. Internal inspection showed that the No. 2 connecting rod had separated from the crankshaft. Evidence of thermal stress and discoloration was found on the No. 2 connecting rod shank and the No. 2 connecting rod bearing, which had separated from the journal. Additionally, thermal discoloration and metal deformation were noted on the No. 1, 2, and 3 connecting rod bearings, as well as the center bearing.
The engine was found to be mostly devoid of oil. The oil sump exhibited severe saltwater corrosion and contained a three-inch wide hole. The oil pump showed heavy resistance and contained non-ferrous fragments and rust, though it functioned normally after cleaning. While the engine damage was consistent with lubrication deprivation, investigators could not identify a specific blockage or malfunction in the oil system due to the damage caused by saltwater submersion.