GLENNS FERRY, ID, USA
N3896V
Bell 206B
While in cruise flight, the helicopter experienced a yawing tendency, vibration, and loss of engine power. The pilot said that he closed the throttle and initiated an autorotation. The helicopter then nosed down, and the pilot pulled back on the cyclic. The auto relight cockpit warning light illuminated, and the pilot increased the throttle to full power. The helicopter began to yaw again, and the pilot closed the throttle; however, the helicopter nosed down. The pilot increased throttle control and raised the collective to regain level flight as the helicopter landed hard and rolled over. The engine and airframe were inspected and no evidence of a mechanical failure or malfunction was found. Fuel drained from the helicopter was found to be dark gray in color, and it contained very fine suspended particulate matter. Inspection of the fuel truck revealed that the filters and the fuel drained from the sump contained heavy contamination. Analysis of the fuel from the helicopter and from the fuel truck revealed the presence of water and fungi.
On August 22, 1996, approximately 1345 mountain daylight time, a Bell 206B, N3896V, registered to Farm Development Corp. and operated by Idaho Helicopters as a 14 CFR Part 91 positioning flight, collided with the terrain 4 miles south of Glenns Ferry, Idaho, after experiencing a yawing tendency and a loss of engine power. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The commercial pilot and one of his passengers were not injured, the second passenger was seriously injured. The pilot reported that he had finished spraying fields and landed to attach the doors and pick up his ground crew to fly them back to base. The pilot reported that while en route at approximately 150 feet above ground level, and between 60 and 70 mph, the helicopter developed a "severe vibration." The pedals cycled abruptly and the helicopter experienced a loss of tail-rotor effectiveness and began to spin to the left. The pilot increased the collective control to arrest the spin. When the helicopter regained direction of flight, the pilot stated that he closed the throttle and initiated an autorotation. The pilot stated that the helicopter then nosed down and he pulled the cyclic back against the rear stop. The cockpit warning auto relight light illuminated and the pilot applied full throttle power. The helicopter began to yaw and the pilot again closed the throttle. The helicopter then nosed down and the pilot increased the throttle control and raised the collective control. The helicopter was at a level attitude and yawed to the left when it landed hard. The right side skid dug into the ground and the helicopter rolled over and came to rest on its right side. A Federal Aviation Administration inspector from the Boise, Idaho, Flight Standards Field Office, documented the accident site and reported that it appeared that the helicopter was traveling in an easterly direction at the time of ground impact. Ground signatures indicate that the stinger contacted the ground first and left a 35-foot indication in the soil. Marks from the landing skids followed for 133 feet. At the end of the skid marks, main rotor blade strikes were noted in the soil, and the helicopter was laying on its right side. The tail rotor had separated and was found 67 feet further east. The wreckage was moved to a secured facility in Boise, where an engine teardown inspection was performed. During the inspection, 19 gallons of fuel were drained from the fuel tank. The airframe fuel filter was inspected and fuel was drained from the filter bowl. The fuel was noted to be dark gray in color and contained very fine suspended particulate matter. Fuel collected from hoses and tubes on the engine, all the way to the fuel nozzle, also contained the gray colored fuel. Fuel samples were gathered from various areas of the airframe and the servicing fuel truck and they were sent for analysis. The fuel control unit and governor were removed and sent to Allied Signal for inspection. At the conclusion of the engine teardown, there was no evidence found to indicate a mechanical failure or malfunction. (See attached Preliminary Accident Investigation Report, Allison Engines). The inspection of the fuel control unit at Allied Signal found that the unit contained the similar gray colored fuel, and an unknown sticky oily substance was found on the fly weights. Samples were taken for analysis. At the completion of the inspection, there was no evidence found to indicate a mechanical failure or malfunction (see attached Preliminary Component Run and Teardown Report for Allied Signal Inspection of FCU and Governor Control). A Federal Aviation Administration Aviation Safety Inspector from the Boise Flight Standards Field Office inspected the fuel truck used to fuel the helicopter. During the inspection, several discrepancies were noted. Two of the discrepancies noted were that the filters and the fuel drained from the sump contained heavy contamination (see attached Fuel Truck Inspection Report). The helicopter's data recorder was removed from the helicopter and sent to Avionics Specialties for readout. It was determined that at 1344:38, the N1 tachometer decreased below 70% and caused the computer to assume that a cooldown/shutdown was in progress. The second record at 1344:44 indicated a "power fail" and the time that power was removed from the computer. The data did not show that any yellow warnings were in progress at the time that power was removed. Examination of the remainder of the data log showed normal operational entries. The computer indicated that the computer run time for the day of the accident was 3.1 hours (see attached Avionics Specialties Analysis Report, Data Recorder). Results of the fuel analysis indicated that the fuel was contaminated with water and fungi (see attached South Bend Materials Technology Center Project Report).
fuel contamination, due to improper servicing of the helicopter, which resulted in an intermittent loss of engine power. A factor relating to the accident was: the pilot's inadequate control of the helicopter, during autorotation with intermittent engine power.
Source: NTSB Aviation Accident Database
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