Taholah, WA, USA
N5225C
Hughes 369D
The pilot of the Hughes 369D helicopter had been engaged in logging operations for about an hour when the engine flamed out, and he executed a hard landing to a nearby road. Post-crash examination found no fuel within the fuel tank, and the fuel quantity sending float entangled in the unsecured start pump wiring preventing the float from registering anything less than about 120 pounds of fuel (about 60 pounds above the Low Fuel Warning light activation setting). The helicopter had undergone a 100-hour inspection just before the accident flight during which the fuel quantity sending unit had been replaced. The maintenance manual contained procedures including a caution to secure the start pump wiring to prevent entanglement with the float, but this caution was addressed only in the start pump replacement procedure of the manual and not included in the fuel quantity sending unit replacement procedures.
On April 7, 2003, approximately 0905 Pacific daylight time, a Hughes 369D helicopter, N5225C, registered to/operated by Olympic Air, Inc., and being flown by a commercial pilot, sustained substantial damage during a hard landing following a total loss of power while engaged in log-slinging operations approximately six nautical miles north of Tahola, Washington. The pilot was uninjured. Variable meteorological conditions existed at the accident site and a company VFR flight plan was in effect. The flight was operated under 14 CFR 133, and had originated from Central Park, Washington, approximately one hour previous to the accident. The helicopter had just undergone a 100-hour inspection on April 4, 2003, at an aircraft total time of 11,325.3 hours. It was then flown on a check flight and subsequently ferried from Aberdeen, Washington, to the vicinity of the accident site. At the site, it was flown through 10 log slinging cycles. The pilot reported that at the conclusion of the 10th cycle the engine flamed out and then immediately restarted. He then aborted the mission and initiated a return to the staging site, which he missed "...in the rain and excitement...." The engine then quit again and the pilot executed an autorotation landing to a dirt road. The landing was hard and the left skid collapsed during the touchdown (refer to photograph 1). The pilot also reported approximately 120 pounds of fuel aboard at the time according to the helicopter's fuel gauge. Post-crash examination revealed no fuel within the fuel cell. Additionally, the fuel quantity indicator sending unit (float and arm) within the fuel tank was observed entangled in the electrical power supply lines to the fuel start pump (refer to graphic image I). The fuel quantity indicator sending unit was found to be restricted such that the float and arm provided an erroneous fuel quantity reading, which bottomed out around 100-120 pounds and no lower. The low fuel warning annunciator light was triggered by the unit's reaching approximately 60 pounds of fuel remaining. The maintenance manual for the Hughes 369D helicopter contained procedures for securing the electrical power supply lines to the fuel line to prevent interference with the fuel quantity indicator sending unit (refer to ATTACHMENT MM-I). The procedure also contained a caution as follows: CAUTION "Ensure start pump wire lead is wrapped around or tie-wrapped to fuel supply hose so that there is no possibility of its interfering with fuel quantity transmitter float mechanism." (Refer to ATTACHMENT MM-I). This caution was specifically related to the "Start Pump Installation" procedure found in the "Fuel System" section of the Boeing Company MD-369D maintenance manual. There was no corresponding caution or reference in the "Fuel Quantity Transmitter Replacement" section of the procedure in the "Fuel System" section of the Boeing Company MD-369D maintenance manual. A review of the helicopter's airframe records dating back to 1996, revealed no documentation of maintenance, repair or replacement of the fuel system start pump. According to the airframe log the "fuel sender" (i.e., fuel quantity transmitter) was removed and replaced due to erratic fuel readings. This was accomplished at the 100-hour inspection completed immediately prior to the loss of power (refer to ATTACHMENT AL-I). The maintenance manual for the Hughes 369D helicopter also specified procedures for the inspection of the fuel system (refer to ATTACHMENT MM-II). The only reference related to the start pump electrical lines was noted on the first page under "Fuel System General Inspection." Specifically, item (5) read: "If start pump wire is ty-rapped [sic] to start pump line, inspect security and condition of ty-raps [sic]." (Refer to ATTACHMENT MM-II). Section (5) provided no guidance in the event that the start pump wires were found unsecured. Additionally, the only reference relating to the fuel system found within the "Continued Airworthiness Inspection" section of the Boeing Company Maintenance Manual for the Hughes 369D helicopter was noted in the "Yearly (Annual) Inspection Checklist." The last annual inspection conducted on N5225C was documented in the airframe log as occurring on February 24, 2003, at an aircraft total time of 11,227.6 hours.
The entanglement of the fuel quantity sender float in the start pump wiring within the fuel tank as a result of the wiring not being properly secured. This rendered the fuel gauge inaccurate and the low fuel warning light inoperative which led to fuel exhaustion. The improper securing of the wiring was a result of unspecified maintenance personnel not identifying the unsecured condition. Contributing factors were the lack of adequate guidance in the maintenance manuals on inspection of the wiring and the low rotor RPM during the autorotation resulting in a hard landing.
Source: NTSB Aviation Accident Database
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