Accident Summary
On July 31, 2023, at 1130 eastern daylight time, a Piper PA-12 airplane, registration N3036M, sustained substantial damage during a forced landing in the ocean near Myrtle Beach, South Carolina. The commercial pilot, who was the sole occupant, received minor injuries. The aircraft was conducting a banner tow operation under Title 14 Code of Federal Regulations Part 91.
According to the pilot, while towing a banner approximately 500 ft above ground level parallel to the coastline, the engine lost power. The pilot managed to restart the engine once, but it lost power again shortly thereafter, prompting a forced landing in the water. The airplane came to rest just offshore, resulting in substantial damage to the fuselage.
Fuel System Examination
The mechanic who recovered the airplane from the ocean reported no visible fuel sheen on the water and no odor of fuel around the aircraft. Upon removing the fuel caps and inspecting the wing tanks with a flashlight, both tanks were found intact but completely empty. No fuel drained when the wings were removed, and the fuel lines were intact. The fuel selector was in the "both" position, and both fuel sight gauges showed empty.
The pilot stated that he refueled the airplane the day before the accident and conducted a preflight inspection on the morning of the accident before the first flight—the accident flight being the second of the day. During the preflight, he visually checked both fuel tanks and sampled fuel from the sump drains, finding no water or debris. He reported departing with 33 usable gallons of fuel.
After recovery, a mechanic removed the carburetor drain plug and found the carburetor full of seawater, with no fuel in the firewall fuel strainer (gascolator). The engine crankshaft rotated freely when manually turned.
Detailed Examination by the NTSB
The National Transportation Safety Board (NTSB) examined the aircraft at a salvage facility. Fuel system continuity was confirmed from both wings to the engine. Both fuel selectors were in the "on" position. The fuel strainer was undamaged and attached; its bowl was half-full of 100LL fuel mixed with a small amount of water, and the screen was clear. The line between the fuel strainer and carburetor contained a small amount of fuel. When shop air was blown through the fuel lines at the wing root, fuel spray emerged from the fuel strainer.
The carburetor was removed; its drain plug was corroded and could be pulled out by hand. There was no fuel in the drain, and the finger screen was clean. Disassembly revealed a small amount of rust-colored fluid in the injector chamber, along with corrosion.
The engine's crankshaft was manually rotated via the propeller flange. It turned about 180 degrees before locking up, preventing full establishment of valvetrain continuity or thumb compression. Borescope inspection of each cylinder found some debris in the No. 3 cylinder. However, no preimpact mechanical malfunctions or failures that would have precluded normal operation were identified.
Conclusion
The investigation did not determine a specific cause for the engine failure. The aircraft was substantially damaged and the pilot was injured. The findings documented fuel exhaustion, post-impact seawater contamination, and corrosion, but no evidence of a pre-existing mechanical issue.