CEN22LA233

The pilot stated that during a nonprecision instrument approach to the destination airport, he applied full engine power when he noticed that the airplane airspeed was decreasing. He realized that the engine lost power and was unsuccessful in attempts at regaining engine power. He performed a forced landing on a pasture during which the airplane sustained substantial damage that included damage to the right wing. A postaccident examination of the wreckage revealed streaks fuel on the left side of the engine cowling. An examination of the engine revealed the fuel control assembly was leaking at the mixture control shaft’s O-ring. The O-ring was intact and did not exhibit separation. However, the outside diameter of the O-ring was less than the diameter of the mixture control shaft consistent with wear. A leak within the fuel control assembly would have allowed air to enter/fuel to exit the assembly resulting in improper fuel metering and a loss of engine power. No other mechanical anomalies were noted with the airframe and engine that would have precluded normal operations. Maintenance records showed that the last overhaul of the fuel control assembly was performed during an engine overhaul in 1996. There were no subsequent records or evidence that indicated the assembly was overhauled after 1996. The engine manufacturer’s recommended time between overhaul (TBO) was 12 years. The engine manufacturer’s standard practice manual stated that engine accessories must be overhauled at the time of engine overhaul. The engine and fuel control assembly exceeded the engine manufacturer’s recommended TBO.

On June 4, 2022, at 0900 central daylight time, a Beech A36, N9087S, was involved in an accident near Amarillo, Texas. The airplane sustained substantial damage. The pilot and pilot-rated passenger were uninjured. The airplane was operated under Title 14 Code of Federal Regulations Part 91 as a personal flight. The pilot stated that during an RNAV approach to runway 35 at the destination airport, he attempted to apply full engine power when he noticed that the airspeed was decreasing. He realized that the engine lost power and he was unsuccessful in his attempts at regaining engine power. He performed a forced landing on a pasture about 2-3 miles from the airport, during which the airplane sustained substantial damage that included damage to the right wing. Postacccident examination of the airplane revealed that the left side of the engine cowl had a blue stain, consistent in color with 100 low lead aviation fuel, that extended in the aft direction. A postaccident engine run was attempted but could not be completed due to fuel leaking from the fuel control assembly. The fuel control assembly was removed from the engine for bench testing. An attempt was made to bench test the fuel control assembly, but due to fuel leaking from the control arm shaft, the bench test could not be performed. The safety wire around the fuel control assembly had a metal stamp with “TCM,” which indicated that the last assembly of the fuel control assembly was performed by Teledyne Continental Motors (TCM). Disassembly of the fuel control assembly revealed that the leak was at the mixture control arm shaft O-ring, which was intact and did not exhibit separation. The outside diameter of the O-ring was less than the diameter of the mixture control shaft. TCM records showed that in 1996 the engine and engine accessories were overhauled, which included the fuel control assembly. An engine logbook entry dated July 15, 1996, stated that the engine was installed onto the airplane. An engine logbook entry dated April 1, 2013, noted a tachometer and an engine total time of 772.0 hours. The time since major overhaul (TSMOH) was recorded as “NA.” The logbook entry stated that all work was done in accordance with the TCM IO-520 overhaul manual and that an annual inspection was performed. The entry did not state that an engine overhaul was performed. Subsequent logbook entries referenced the TSMOH of the April 1, 2013, entry. No evidence could be found to indicate that the fuel control assembly had been overhauled since 1996. TCM’s recommended time between overhaul, as stated in Continental Motors Aircraft Engine Service Information Letter SIL98-9C, was 12 years. Several sections in TCM’s Standard Practice Manual stated that the engine accessories must be overhauled at the time of engine overhaul.