Eupora, MS, USA
N57PH
BELL 206
During an aerial application flight, the helicopter's engine lost power while flying about 50 feet above the ground. The pilot stated that the helicopter dropped straight down, and that the rotor stopped turning during the descent. The helicopter was substantially damaged during the impact sequence. A postaccident examination of the helicopter's fuel system revealed a brown contaminate, of a density greater than jet fuel. The contaminate was present in several airframe and engine fuel filters and on the engine fuel nozzle. Examination of the dual use truck that was used to service the helicopter with fuel and herbicide revealed that the fuel filter between the Jet-A fuel tank and the fuel delivery hose was also contaminated. A common trough that ran along the top of the fuel truck provided an area where any over flow of water used to fill the truck's herbicide tank could be introduced into the truck's Jet-A fuel tank through gaps in the fuel tank's cap seal.
On October 25, 2009, about 1733 central daylight time, a Bell 206B-3, N57PH, operated by Provine Helicopter Service, Inc, was destroyed after a forced autorotation following a total loss of engine power near Eupora, Mississippi. The certificated commercial pilot was seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the aerial application flight, which was conducted under the provisions of Title 14 Code of Federal Regulations Part 137. A written statement provided by the operator indicated that the pilot conducted a preflight inspection of the helicopter about 0700 on the morning of the accident. He drained approximately one quart of Jet-A fuel from the helicopter to check for water and contaminants, and concluded that the fuel was "clean and void of water." The pilot then attempted to start the helicopter, and contacted the company's mechanic when it would not start. The mechanic spent the morning performing maintenance on the helicopter, after which it was fueled with 16.7 gallons of Jet A. Around 1300, the pilot departed to the job site, a tract of land to the northeast, to conduct the aerial application flights. The pilot began the applications about 1400, and treated approximately 115 acres with approximately 1,725 gallons of herbicide prior to the accident. During the process, the helicopter was refueled three to four times, with approximately 15 gallons of Jet-A fuel at each filling. The fuel was obtained from a fuel truck located at the application site. The fuel truck was also equipped with a separate tank that held herbicide used for the aerial applications. The pilot had just refilled the spray tank with approximately 90 gallons of herbicide and was conducting his first turn at the edge of the land tract when the helicopter's engine "completely lost power." The pilot called out on his radio that he was "going down and needed help" and attempted guided the helicopter to a clearing. He stated that the rotor "stopped turning completely" approximately 50 feet above the ground. The helicopter then dropped "straight down" and landed on the skids. A member of the ground crew, who drove the fuel truck and was responsible for servicing the helicopter with fuel and herbicide, stated he began his day by performing a pre-trip inspection of the truck shortly after 0500. As part of the inspection, the crewman drained about one-half gallon of Jet-A fuel from the 500 gallon fuel tank and inspected the fuel with a flashlight. He also repeated the procedure while draining fuel from the fuel filter, this time with about a quart of fuel. Both samples were absent of water or debris. The crewman subsequently drove the fuel truck to the remote site to meet the helicopter. After learning later in the morning that the pilot was having difficulty starting the helicopter, and that the problem was reportedly related to a fuel nozzle, the crewman drained a fuel sample from both the fuel tank and filter a second time, again noting no debris. A Federal Aviation Administration (FAA) inspector who responded to the accident scene reported that the helicopter came to rest upright, and the fuselage exhibited extensive crush damage. A fuel sample obtained from the airframe fuel filter contained a mixture of fuel and a brown contaminant. When the sample was placed in a jar, the contaminate and the fuel separated, with the contaminate settling to the bottom of the jar. A similar brown contaminate was also observed in the engine fuel pump filter, fuel control unit screen, and on the engine fuel nozzle screen. The fuel truck used during application operations to supply the helicopter with fuel and spray chemical while in the field was owned by the operator. A 500-gallon fuel tank was located a the foreword end of the truck, while a tank for mixing water and spray chemical was located at the aft end. A common trough ran along the top portion of both tanks, which would retain any over-fill of water or fuel, and was drained through two small holes at the forward end. Examination of the cap for the fuel tank revealed that the o-ring seal and the fuel vent were deteriorated, and that the seals were not continuous. The fuel tank was configured in a way that fuel was taken directly from the lowest point in the tank, and pumped through a filter to the fuel filler hose. No standpipe was present at the bottom of the tank that would have prevented any collected water from entering the fuel filter, and no pressure gauges or sensors were installed up or downstream of the filter. The truck-based fuel tank was checked for the presence of water using a water finding paste applied to a dip stick. A small amount of water was detected. The fuel filter between the tank and the delivery hose was removed and examined. The filter element appeared "bulged" and water was present in the filter. The brown contaminant was present throughout the paper folds of the fuel filter, and was collected along its interior. According to the operator, the fuel truck's Jet-A fuel tank was most recently serviced with 198 gallons of fuel from the operator's fueling station on the day before the accident flight. The pilot held a commercial pilot certificate with a helicopter rating. He reported approximately 2,600 hours in the accident helicopter make and model. His most recent second-class FAA medical certificate was issued in February, 2008. The nearest weather reporting station, located approximately 45 nautical miles from the accident location, reported clear skies, 10 statute miles visibility, and calm winds about the time of the accident.
A loss of engine power due to fuel contamination of the helicopter’s fuel supply.
Source: NTSB Aviation Accident Database
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