Amateur-built S1S N401MS accident near Carbondale, Illinois

Probable cause

A loss of engine power due to fuel starvation resulting from an uncommanded change to the fuel servo mixture position due to the improperly installed mixture cable.

NTSB analysis

The pilot reported that he had completed three touch-and-go landings followed by a low approach. As he began a climb after the low approach, the engine lost power about 400 feet above ground level (agl). The pilot was able to momentarily restore partial power by manually actuating the emergency fuel pump; however, the engine lost power again. He was unable to restore engine power and executed a forced landing on an airport perimeter road. The airplane subsequently struck a power pole which resulted in substantial damage to the airframe.

A postaccident examination of the engine revealed no mechanical anomalies. No fuel was present in the fuel manifold when the fuel manifold was disassembled. Further examination revealed that the mixture control cable was not secured at the fuel injection servo. Movement of the cockpit mixture control resulted in corresponding flexing of the mixture cable outer sheath at the engine fuel injection servo. With the cockpit mixture control in the full rich position, the engine fuel injector mixture lever position corresponded to about mid-range. A full rich mixture setting at the fuel injector could not be achieved. Maintenance logbooks indicated that several fuel lines were replaced and a fuel flow transducer was installed about 3.6 hours before the accident.

It is likely that the failure of the mixture cable sheath to be properly secured at the fuel injection servo allowed the cable to flex, resulting in an uncommanded change in the fuel servo mixture during the flight, resulting in a loss of engine power due to fuel starvation.

Text from the NTSB. Open the NTSB docket for CEN26LA074 for the full record.