ERA24LA331

An insect nest in the right main fuel tank’s vent line, which resulted in an inaccurate fuel level reading, fuel starvation, and a total loss of engine power.

After filling the fuel tanks, the flight instructor flew the airplane on multiple flights with different fuel tanks selected, including the right main fuel tank, with no discrepancies. The instructor and a pilot who was receiving familiarization training in the airplane then departed with the fuel selector on the right main fuel tank. They performed airwork with the fuel selector on a different tank before switching back to the right main fuel tank for an approach and landing. Before departing again, the pilot and instructor reviewed the fuel quantity indications and decided to keep the fuel selector on the right main tank position because the indicated quantity appeared sufficient to sustain engine operation. After departure, the flight remained in the airport traffic pattern. After turning onto the downwind leg, the engine lost power, regained it momentarily, then lost power completely. Turning on the auxiliary fuel pump did not restore engine power. The flight instructor took control of the airplane and elected to land in a field after determining the airplane could not reach a closed runway at the airport. After touchdown, the airplane bounced then came to an abrupt stop with substantial damage to both wings and the fuselage. Postaccident examination of the airplane determined that the right main fuel tank had collapsed inward despite no corresponding damage to the surrounding wing structure and wing skin. Further examination of the right main fuel tank’s fuel vent line utilizing compressed air found that an insect nest had extensively blocked it. This blockage would have prevented air from entering the tank as fuel was consumed and allowed a partial vacuum to develop inside the tank. The inward collapse also trapped the fuel quantity transmitter arm, and resulted in the fuel quantity gauge indicating more fuel than was actually present. As fuel continued to be consumed from the unvented tank, the erroneous fuel quantity indication prevented the flight crew from accurately assessing the remaining usable fuel. Before the takeoff that preceded the loss of engine power, the pilots selected the right main fuel tank based on the indicated fuel quantity, although the tank actually contained insufficient usable fuel. After departure, the engine lost total power due to fuel starvation when the fuel remaining in the selected tank was exhausted. Although the pilots activated the auxiliary fuel pump and the instructor directed the left-seat pilot to select another fuel tank, selection of the right fuel tank did not occur before the pilots’ attention became solely focused on executing the forced landing.

On July 26, 2024, about 1324 eastern daylight time, an Aero Commander 200D airplane, N326WR, was substantially damaged when it was involved in an accident near Valdosta, Georgia. The flight instructor and the pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that, after topping all four fuel tanks three days earlier, he flew three traffic patterns at Atlanta Regional Airport-Falcon Field, Atlanta, Georgia. Earlier on the day of the accident, with about 70 gallons of fuel on board, he flew the airplane uneventfully to Valdosta Regional Airport (VLD), Valdosta, Georgia, with different fuel tanks selected during the flight, including the right main fuel tank; he noted no abnormalities on that flight. After landing, he secured the airplane and met with the pilot he intended to conduct a familiarization flight with and briefed him about the airplane and how to perform a preflight inspection. The pilots boarded the airplane for the familiarization flight and departed with the fuel selector on the right main fuel tank. After climbing to 5,500 ft mean sea level, the pilots switched the fuel selector to the left auxiliary fuel tank and then performed airwork. After about 50 minutes, the pilots returned to VLD with the fuel selector set to the right main tank during the approach and landing. They taxied back and, before departure, elected to leave the fuel selector in the right main fuel tank position based on the right main fuel quantity indicator, which reflected about 14 gallons of fuel remaining; the onboard recorded data indicated 16 gallons remaining. The pilots reported selecting the right main fuel tank because it indicated the greatest quantity of fuel remaining. Shortly after turning onto the downwind leg of the airport traffic pattern , with the pilot flying the airplane, , the engine lost power, regained it momentarily, then lost power completely. At the time of the total loss of engine power, the on-board recorded data indicated that the left fuel quantity was reading 17 gallons. The instructor took control of the airplane and turned toward the airport and performed the emergency memory items, which included turning on the auxiliary fuel pump and asking the pilot to switch fuel tanks. The instructor directed the pilot to select another fuel tank while they were performing the emergency procedures. The pilot stated that the fuel selector was not repositioned before landing because of the limited time available while executing the forced landing. After touchdown in the field, the airplane bounced after contacting a road then came to an abrupt stop. Postaccident examination of the airplane revealed substantial damage to both wings and the fuselage. The right main fuel tank contained no fuel. With electrical power applied the right main fuel tank quantity gauge indicated 18 gallons. Further examination of the right main fuel tank revealed the upper and lower sides of the tank in the center were compressed inward while there was no corresponding damage to the upper and lower wing skins. When compressed air was forced through the right main fuel tank vent line, it exhibited extensive blockage by an insect nest. The examination further revealed that the deformation of the right main fuel tank had trapped the fuel quantity transmitter float arm in a position consistent with it indicating more fuel than was actually present. Operational testing of the fuel quantity transmitter revealed it functioned properly.