N912RG – Tl Ultralight Sting RG – 2024-06-26 NTSB Accident Report

On June 26, 2024, about 0956 Pacific daylight time, an experimental amateur-built Sting RG, N912RG, was substantially damaged when it was involved in an accident near Rio Linda, California. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, he departed for an approximate 45-minute local area flight with the fuel quantity indicator displaying about 50% (16 gallons) fuel remaining. The pilot further reported that due to the design of the fuel tank installation, he was unable to directly verify the fuel quantity by visual inspection or use of a dipstick. During the flight, he performed several takeoffs and landings at a nearby airport. The pilot reported that when the fuel quantity indicator showed slightly above 25% remaining, he elected to return to Rio Linda Airport (L36), Rio Linda, California. The pilot configured the airplane for a short field landing to runway 17 when the engine “stuttered” and then lost power. The pilot stated that he was at a low altitude, that the airspeed was deteriorating, and that he decided to initiate a forced landing to a field. During the landing, the airplane struck a softball field perimeter fence and came to rest upright. The airplane sustained substantial damage to the left wing. Additionally, the pilot reported that although the fuel quantity indicator displayed about 25% fuel remaining, the airplane ran out of fuel.

The airport manager, who was also an airframe and powerplant mechanic and rated pilot, arrived at the accident site shortly after the accident. The airport manager reported that the pilot told him that he ran out of fuel, and that the fuel quantity indicator showed that there was still fuel on board. While assessing the accident site and during recovery of the airplane, the airport manager did not notice any signs of fuel leaking from the airplane or the odor of fuel. While the airport manager was in possession of the airplane, he removed the fuel sump located on the lower fuselage. The fuel sump was opened and no fuel was observed.

The airplane was equipped with extended fuel tanks, totaling 30.5 gallons of fuel. Due to the fuselage fuel tank layout, visual examination of the fuel level was not possible. The engine operator’s manual states in part that fuel burn was about 7.1 gallons per hour at takeoff power settings and 4.9 gallons per hour at 75% power.

Following the accident, the airplane was been sold and partially disassembled before examination. Examination of the partially disassembled airplane revealed that the fuel float assembly was found disconnected at the fuel hose and breather hose. The fuel float assembly was removed for further examination. Examination of the fuel float assembly revealed that the fuel sensor arm was intact with a float attached at the end, and the arm moved freely when actuated by hand. The fuel float assembly was then connected to an external battery source. When the battery power was applied, the fuel low-level light illuminated; however, the fuel quantity indicator did not respond, even when the fuel sensor arm was manually moved. An ohmmeter was used to check the fuel float assembly contacts, and resistance was measured; however, the resistance reading remained unchanged when manually moving the fuel sensor arm between the empty and full quantity levels. About 5 gallons of water were added to the main fuselage fuel tank. Water leaked from the area by the nose landing gear assembly near the location where the landing gear had collapsed into the lower fuselage, consistent with impact damage to the tank.

Examination of the recovered engine revealed that it remained attached to the engine mount and airframe. For recovery purposes, personnel separated the engine and engine mount from the airframe. The crankshaft was rotated by hand using the propeller hub. Rotational continuity was established throughout the engine and valvetrain. Thumb compression and suction were obtained on all four cylinders. Fuel-system continuity was established from the fuel pump to the carburetors. Recovery personnel separated the fuel feed line to the fuel pump during recovery operations. The fuel pump was removed and manually actuated. No fuel exited the outlet port when the plunger was activated. The carburetor float bowls were removed and inspected. Both carburetor bowls were free of fuel and debris. The main jets in both carburetors were visually examined and found free of obstruction.

No mechanical malfunctions or failures with the engine were observed that would have precluded normal operation.