What happened
On November 19, 2022, a Piper PA-30, registration N7295Y, was involved in a fatal accident near Smith Reynolds Airport (INT) in Winston-Salem, North Carolina. The flight, operated as a Part 91 personal flight, had previously traveled from St. Louis to London, Kentucky, where the pilot had noted an electrical system issue earlier that day.
During the approach to Winston-Salem, the pilot notified air traffic control that one engine was not producing as much power as the other. The pilot initially requested to land on runway 4 but instead continued past the centerline and requested runway 33. While maneuvering east of the airport, a witness observed the aircraft bank left at a 45-degree angle before rolling to an inverted position and descending straight down into a backyard near a line of trees. The aircraft sustained substantial damage, and the pilot and passenger were 2 fatal.
The investigation
Investigators examined the wreckage and found the landing gear was extended and the flight controls were functional. While the left engine showed evidence of producing power at impact, the right engine was windmilling. The investigation focused on the right engine's fuel servo, which was found to have failed an idle circuit test during post-accident operational testing. Specifically, the fuel flow was approximately 2.6 times higher than specified when the throttle was moved to idle.
Upon disassembly of the right fuel servo, investigators discovered small pieces of acrylonitrile-butadiene-styrene (ABS), a thermoplastic, inside the fuel side of the regulator section. After this foreign debris was removed and the unit was reassembled, the fuel flow returned to within limits. Additionally, investigators noted a 0.011-inch clearance in the throttle valve gap, which was likely an attempt by maintenance personnel to correct the excessive fuel flow.
Findings
- The right engine experienced a total loss of power due to excessive fuel flow caused by contamination and/or misalignment of the fuel servo regulator.
- The pilot did not feather the right propeller, or delayed doing so until the engine RPM dropped below the speed required to disengage the propeller's start locks.
- The unfeathered, windmilling propeller created significant parasitic drag, making level flight difficult.
- The aircraft's airspeed likely dropped below the Velocity Minimum Control (Vmc) speed during maneuvers, leading to a loss of control.