KELLER, WA, USA
CGKQH
BELL 204B
THE PILOT WAS CONDUCTING FIRE FIGHTING MULTIPLE WATER DROPS USING AN EXTERNAL LOAD 'BAMBI BUCKET'. EARLY THAT DAY THE BUCKET'S CINCH STRAP HAD BEEN REPLACED. ON THIS DROP THE PILOT RADIOED THAT HE WAS HEAVY...3600 POUNDS. A PUFF OF SMOKE WAS OBSERVED, AND THE HELICOPTER CRASHED. INVESTIGATION REVEALED THAT A LOSS OF POWER HAD OCCURRED DUE TO THE LOSS OF ALL 2ND TURBINE ROTOR BLADES, PRECIPITATED BY A STRESS RUPTURE FAILURE OF 3 CONSECUTIVE BLADES INDUCED BY HIGH OPERATING TEMPERATURES. THE CINCH STRAP WAS BOUGHT AT A HARDWARE OR SPORTING GOODS STORE - IT WAS NOT THAT PROVIDED BY THE MANUFACTURER. DISASSEMBLY OF THE BUCKET CONTROL HEAD WIRING ASSEMBLY REVEALED EVIDENCE TO SUPPORT INTERMITTENT OPERATION.
THE TOTAL LOSS OF ENGINE POWER DUE TO TURBINE BLADE SEPARATION WHILE THE PILOT WAS OPERATING IN THE AIRCRAFT AT A GROSS WEIGHT THAT EXCEEDED PERFORMANCE SPECIFICATIONS FOR EXISTING METEOROLOGICAL CONDITIONS. FACTORS INCLUDE THE FAILURE OR INABILITY TO JETTISON THE EXTERNAL LOAD, THE USE OF AN IMPROPER CINCH STRAP, AND AN IMPROPERLY ASSEMBLED AND MAINTAINED WIRING CONNECTOR.
Source: NTSB Aviation Accident Database
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