ERA09FA068 · Beech 95-B55 (T4

During flight in instrument meteorological conditions, the left engine experienced a total loss of power due to the separation of the flexible fuel supply hose between the left engine firewall fitting and the engine-driven fuel pump inlet fitting due to an inadequately torqued B-nut. The pilot informed air traffic control of a discrepancy, although he was not specific in the nature of the problem. A momentary change in heading to the left occurred consistent with the pilot’s failure to maintain directional control of the airplane following the loss of left engine power. Radar data indicated that the airplane was allowed to decelerate, followed by a loss of lateral and directional control and a subsequent flat spin to the left. The stall warning horn was recorded during the pilot's comment to the controller that he was in a spin. The airplane descended uncontrolled and crashed into a wooded area behind a home and was destroyed by impact and a postcrash fire. No preimpact mechanical failure or malfunction of the airplane or of either engine was noted.

Acoustic analysis of engine rpm signatures reflect a steadily decreasing rpm to 1,760, most likely from the left engine, which is below the normal operating range. The analysis indicated an rpm signature of 2,140, most likely from the right engine, which was in the normal operating range. The pilot neither feathered the left propeller nor secured the left engine following the total loss of power per the Pilot's Operating Handbook and Aircraft Flight Manual, and there were no mechanical discrepancies with the propeller or propeller governor that would have prevented him from doing so. Operational testing of the left engine with an exemplar flexible fuel hose that was finger-tight resulted in the separation of the line from the inlet fitting. The test runs determined that when finger-tight the B-nut loosened and tightened varying amounts with different power applications. Rebuilt engines were installed 9 months earlier and there was no entry indicating that the flexible fuel hoses were replaced at that time. There was no record that the left flexible fuel hose was ever replaced since the airplane was manufactured in 1978. Although the airplane manufacturer recommends that flexible fuel hoses be replaced when conditions warrant, at engine overhaul, or 5 years, whichever occurs first, there is no evidence to suggest that the age of the hose contributed to its separation from the engine-driven fuel pump inlet fitting.

Verbatim NTSB analysis and probable cause from the NTSB dataset