Accident Overview
On May 11, 2023, at 1210 central daylight time, an experimental, amateur-built 5151 Mustang, registration N91026, was substantially damaged during a forced landing near Hector, Minnesota. The commercial pilot, who was not the builder of the airplane, reported no injuries. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 test flight.
Preflight and Takeoff
According to a Federal Aviation Administration (FAA) inspector, the pilot had recently overhauled the engine carburetors and modified the aircraft's fuel system. These modifications were not recorded in the maintenance records. After purchasing the airplane, the pilot removed an installed airframe ballistic parachute and replaced it with a fuel tank, calculating that the weight of the parachute was equal to the combined weight of the fuel tank and 2 gallons of fuel.
Before the accident flight, the pilot tied the tailwheel to an anchor point and ran the engine at high power for approximately 28 minutes to test the fuel system modifications. He also adjusted the ground-adjustable propeller to achieve 6,200 rpm. After the ground run, he decided to conduct a test flight. During takeoff with the newly installed fuel tank selected, the engine only reached 6,100 rpm. The pilot stated he suspected something was wrong.
While another aircraft was near the airport, the pilot radioed that aircraft, reporting engine issues and requesting its position. The other pilot responded that it was about 3 miles from the airport. The accident pilot advised the other aircraft to land first and that he would land behind. As he turned toward the runway, the engine experienced a total loss of power, and he was unable to glide to the runway. The airplane touched down in a soft field approximately 250 feet from the end of the runway.
Postaccident Examination
After the accident, the pilot recovered the airplane and placed it in a hangar without the knowledge or permission of the National Transportation Safety Board (NTSB) or FAA. The airplane sustained substantial damage, including a damaged wing rib and lower spar cap at the left main gear attach point.
An FAA inspector examined the engine and found the front carburetor out of its mounting flange, with the securing clamp so loose that the carburetor could be placed back in the flange and removed without loosening the clamp. A portion of the left side engine cowl near the carburetor was torn outward and aft due to impact forces during landing. No other engine anomalies were noted.
Additional Information
The pilot stated his belief that the loss of engine power was due to fuel starvation and that there may have been a problem with the vent of the newly installed fuel tank. The NTSB Pilot/Operator Aircraft Accident/Incident Report (Form 6120) was not received from the pilot.
The previous owner and builder of the airplane did not make the required logbook entry for completing Phase 1 flight testing, limiting operation of the airplane to the flight test area specified in the airworthiness certificate's operating limitations (within 25 nautical miles of Bateman Field, Chippewa Falls, Wisconsin, excluding Class C airspace). The accident flight occurred outside of this authorized area.