What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(.19)On December 23, 1998, at 1151 hours pacific standard time, a Bell UH-1H, N4590, entered an uncontrolled descent, impacted an embankment and rolled into belden reservoir, 7 miles west of Quincy, California. The aircraft was approaching a landing spot when the event occurred. The helicopter was destroyed and the commercial licensed pilot was fatally injured. Visual meteorological conditions prevailed for the external load operation that was conducted by westwind helicopters, inc., under 14 CFR part 133.(.4) while conducting external load operations, the pilot radioed that the engine had failed. Witnesses reported visually observing the main rotor slowing and the individual blades becoming visible before the helicopter descended steeply into a reservoir from about 200 feet AGL. The main rotor driveshaft, main rotor blades, and the tail rotor blades exhibited signatures consistent with low rotor RPM at impact. Engine examination revealed that the gas producer and power turbine assembly had failed as a result of the cumulative effects of thermal stress due to over-temperature operation. Further examination revealed that the exhaust gas temperature harness on the engine had a low signal output resulting in a low EGT indication in the cockpit which caused the company pilots to unknowingly operate the engine in excess of maximum EGT. According to other company pilots who flew this helicopter on typical external load operations, the engine would reach its EGT limit before the maximum torque was achieved. The operator did not routinely perfrom health indicator tests (hit checks) which were developed by the u. s. army to detect changes in engine power output. Review of the helicopter's FAA type certificate data sheet (H15NM) revealed the requirement for hit checks to be accomplished prior to each takeoff and recorded in a log record. (-23) aircraft was reported to iic 1500, 12/23/98. Aircraft was removed from site by towing company and sheriff's department. Released aircraft without authority from FAA or NTSB. Visited aircraft 12/24/98 at cresent towing. Aircraft appeared to be all present. Visited site. Very little at site. The lift basket is at site. Only one witness statement available at this time. This is a preliminary report and amended form 8020-23 will be forwarded upon further investigation.
As the FAA filed it
(.19)ON DECEMBER 23, 1998, AT 1151 HOURS PACIFIC STANDARD TIME, A BELL UH-1H, N4590, ENTERED AN UNCONTROLLED DESCENT, IMPACTED AN EMBANKMENT AND ROLLED INTO BELDEN RESERVOIR, 7 MILES WEST OF QUINCY, CALIFORNIA. THE AIRCRAFT WAS APPROACHING A LANDING SPOT WHEN THE EVENT OCCURRED. THE HELICOPTER WAS DESTROYED AND THE COMMERCIAL LICENSED PILOT WAS FATALLY INJURED. VISUAL METEOROLOGICAL CONDITIONS PREVAILED FOR THE EXTERNAL LOAD OPERATION THAT WAS CONDUCTED BY WESTWIND HELICOPTERS, INC., UNDER 14 CFR PART 133.(.4) WHILE CONDUCTING EXTERNAL LOAD OPERATIONS, THE PILOT RADIOED THAT THE ENGINE HAD FAILED. WITNESSES REPORTED VISUALLY OBSERVING THE MAIN ROTOR SLOWING AND THE INDIVIDUAL BLADES BECOMING VISIBLE BEFORE THE HELICOPTER DESCENDED STEEPLY INTO A RESERVOIR FROM ABOUT 200 FEET AGL. THE MAIN ROTOR DRIVESHAFT, MAIN ROTOR BLADES, AND THE TAIL ROTOR BLADES EXHIBITED SIGNATURES CONSISTENT WITH LOW ROTOR RPM AT IMPACT. ENGINE EXAMINATION REVEALED THAT THE GAS PRODUCER AND POWER TURBINE ASSEMBLY HAD FAILED AS A RESULT OF THE CUMULATIVE EFFECTS OF THERMAL STRESS DUE TO OVER-TEMPERATURE OPERATION. FURTHER EXAMINATION REVEALED THAT THE EXHAUST GAS TEMPERATURE HARNESS ON THE ENGINE HAD A LOW SIGNAL OUTPUT RESULTING IN A LOW EGT INDICATION IN THE COCKPIT WHICH CAUSED THE COMPANY PILOTS TO UNKNOWINGLY OPERATE THE ENGINE IN EXCESS OF MAXIMUM EGT. ACCORDING TO OTHER COMPANY PILOTS WHO FLEW THIS HELICOPTER ON TYPICAL EXTERNAL LOAD OPERATIONS, THE ENGINE WOULD REACH ITS EGT LIMIT BEFORE THE MAXIMUM TORQUE WAS ACHIEVED. THE OPERATOR DID NOT ROUTINELY PERFROM HEALTH INDICATOR TESTS (HIT CHECKS) WHICH WERE DEVELOPED BY THE U. S. ARMY TO DETECT CHANGES IN ENGINE POWER OUTPUT. REVIEW OF THE HELICOPTER'S FAA TYPE CERTIFICATE DATA SHEET (H15NM) REVEALED THE REQUIREMENT FOR HIT CHECKS TO BE ACCOMPLISHED PRIOR TO EACH TAKEOFF AND RECORDED IN A LOG RECORD. (-23) AIRCRAFT WAS REPORTED TO IIC 1500, 12/23/98. AIRCRAFT WAS REMOVED FROM SITE BY TOWING COMPANY AND SHERIFF'S DEPARTMENT. RELEASED AIRCRAFT WITHOUT AUTHORITY FROM FAA OR NTSB. VISITED AIRCRAFT 12/24/98 AT CRESENT TOWING. AIRCRAFT APPEARED TO BE ALL PRESENT. VISITED SITE. VERY LITTLE AT SITE. THE LIFT BASKET IS AT SITE. ONLY ONE WITNESS STATEMENT AVAILABLE AT THIS TIME. THIS IS A PRELIMINARY REPORT AND AMENDED FORM 8020-23 WILL BE FORWARDED UPON FURTHER INVESTIGATION.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.