MIA03LA121 · Piper PA-25-235

The pilot stated that the flight departed with 120 gallons of usable fuel on-board, and approximately 1 hour into the flight while flying between 2,000 and 2,500 feel mean sea level with fuel being supplied from the main fuel tank, he turned on the boost pump and the fuel selector for the larger fuel tank (auxiliary fuel tank). The flight continued and approximately 30-45 minutes later with both fuel tank on/off valves "on", the engine experienced a loss of power. He applied carburetor heat but engine power was not restored. He maneuvered the airplane for a forced landing on an east/west oriented dirt road, but recognized that he would be unable to land on the road due to trees. He set up for landing south of and parallel to the dirt road. While descending, the left wing collided with a tree approximately 20 feet above ground level. He did not recall any other part of the accident but remembers waking up and exiting the airplane. Examination of the airplane at the scene by an FAA airworthiness inspector revealed the original fuel tank installed when the airplane was manufactured was empty, and an aluminum fuel tank installed in place of the hopper tank was full. Examination of the cockpit revealed yellow colored placards with black letters by the 2 fuel on/off valves that indicated usable fuel quantity, orientation in terms of position, i.e. "push-on" and "pull-off"; there was no placard that indicated both should not be on at the same time. Check valves which were oriented properly in terms of flow direction were installed at the outlets of both fuel tanks; both check valves were removed for further examination. Examination of the check valves was performed with FAA oversight at a military installation with calibrated equipment. The check valve from the original fuel tank was found to open at less than 1/4 psi, but the check valve from the auxiliary fuel tank was found to open at 3/4 psi. Review of the maintenance records revealed an entry dated May 25, 2003, which indicates the mechanic removed all optional agricultural equipment and installed a 77-gallon aluminum fuel tank and boost pump in place of the hopper tank. The entry references a FAA 337 form, and that all work was performed in accordance with the airplane type certificate data sheet and flight manual, and Advisory Circular 43.132A. The mechanic who signed off the logbook entry for the 77-gallon aluminum tank installation stated the installation into the accident airplane was based on a previous installation of the same system another mechanic had done to an airplane he owned. The previous installation included stainless steel check valves at the outlet of both fuel tanks and the new owner of the airplane wanted them installed as well. The check valves that were installed were purchased from a Yacht company. As part of the installation in the accident airplane, the mechanic stated that he installed a placard by the fuel on/off valves which indicated that both should not be opened at the same time. Following the installation, the engine was operated with fuel being supplied only from the auxiliary fuel tank and the engine driven fuel pump operating. Static testing showed that with fuel in the fuel tank and the fuel line disconnected downstream of the check valve, but only a trickle of fuel was noted. He questioned that with the representative of the company where he purchased the check valves and the response was that was normal. Further testing with pressure applied to the tank revealed fuel flowed from the disconnected line. Additionally, he stated the pilot had asked him if it was acceptable to have both on/off valves "on" at the same time, and he advised the pilot it was not. Both he and the pilot checked the main fuel tank before the accident flight departed and both noted that the fuel level was down 2-3 inches which he estimated was 4-5 gallons less than full. According to the FAA inspector-in-charge, the installation of the 77-gallon fabricated fuel tank (auxiliary tank) was performed without FAA approved data. He also stated that the airplane flight manual (AFM) did not have a supplement indicating how to operate the auxiliary fuel tank system.

Verbatim NTSB analysis and probable cause from the NTSB dataset