Accident Sequence
During the initial climb after takeoff, the pilot observed that the fuel boost pump warning light flickered on and then off, accompanied by a corresponding surge in the engine. Approximately 20 feet above ground level, engine power was lost and the helicopter impacted the ground.
Fuel System Examination
A functional field check of the fuel system identified a leak in the breakaway valve, which would have allowed air to enter the system. Further examination of the fuel boost pump and breakaway valve revealed deteriorated O-rings. The field inspection also found that the inlet shutoff valve arm on the fuel boost pump was bent.
According to the manufacturer's overhaul manual, if the inlet shutoff valve arm is bent, it may prevent the valve from opening and restrict fuel flow. The component overhaul manuals indicated that the O-ring seals in both the fuel boost pump and the fuel breakaway valve are not required to be inspected during routine inspections and are replaced only as on-condition items.
Component Testing
A hydro leakage test and performance flow test were conducted on the fuel boost pump with the original O-rings. The fuel boost pump did not pass the manufacturer's tests. After replacing the O-ring seals with new ones, the fuel boost pump functioned within manufacturer's limits.
The fuel control unit and fuel pump were tested separately and no discrepancies were found. The fuel nozzle was also tested and flowed within manufacturer's limits.
Maintenance History
Maintenance records disclosed that the last time the fuel boost pump was worked on was five years prior to the accident.