CHI98LA251 · Grumman G-164B

The pilot stated that there was 90 gallons of fuel on board upon departure and that he did nor hear any unusual engine sounds during the loss of engine power. He had completed spraying and was returning to his airstrip at an altitude of 150 ft above ground level for another load when the engine torque reading dropped to 30%. While attempting to increase power, the pilot reported that the engine quit at which time he then preformed an emergency landing to a muddy field Inspection of the engine found the compressor, turbine, accessory gear box and reduction gear box to rotate. The chip detector was examined and was found to be free of contaminants. The fuel lines to the engine, the fuel filter and its respective fuel bowl was unobstructed. No external contaminants were observed to be present on the igniter. The engine pneumatic lines were in place and did not possess any indications of leakage. One blade of the first stage turbine rotor and two blades of the power turbine were fractured. The compressor and turbine housing exhibited twisting without any localized outward deformations or punctures. The fuel-oil heater was found to be intact and upon internal examination a 50/50 ratio of fuel to water was estimated to be present. The high pressure fuel pump and fuel control units were examined by Pratt and Whitney under the supervision of the Transportation Safety Board of Canada and no anomalies were noted. The Transportation Safety Board of Canada concurs with the report which states, 'Dynamic tests to the Fuel Control did not identify any indications that would have precluded appropriate engine performance and goes on to say, 'The gear stage was observed to be in good condition when ignoring the damage created during the suspected field inspection of the pump'. Metallic debris was found to be present in the field inspection of the high pressure fuel filter bowl and is considered to be normal in this area.

Verbatim NTSB analysis and probable cause from the NTSB dataset