SPOKANE, WA, USA
N574H
Enstrom F-28C
The pilot began the takeoff in the helicopter while giving a ride to a passenger at a local festival. About 100 feet above the ground, the engine began to run rough and quit. The helicopter, which was not insured, was damaged when the pilot initiated an emergency descent and impacted trees. The operator claimed that the fuel in the helicopter, his fuel truck, and his ground supply tank had been contaminated with jet fuel prior to the accident. Subsequent NTSB testing revealed that the fuel could not have been contaminated, and that jet fuel must have been added to the helicopter and the operator's self-tested fuel samples after the accident. The engine was examined in detail and tested by NTSB. No evidence of damage due to jet fuel contamination was found. The engine initially ran rough due to a restricted fuel nozzle, then ran within specifications (no turbocharger) after the nozzle was changed. The nozzle restriction was not found. Maintenance discrepancies such as a leaking turbocharger, improperly installed fuel nozzles, crimped fuel vent line, and a separated magneto cap were found, but no conclusive evidence associated with the accident power loss was found.
HISTORY OF FLIGHT On October 5, 1996, about 1500 Pacific daylight time, an Enstrom F-28C helicopter, operated by Custom Aviation, Inc., Spokane, Washington, impacted trees and was substantially damaged near Spokane during an emergency descent. The emergency descent was precipitated by a loss of engine power during climb. The commercial pilot and her passenger were not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The sightseeing flight was conducted under 14 CFR 91. According to a line person employed by the operator, the accident helicopter had been fueled earlier in the day from the operator's fuel truck at Felts Field in Spokane. The line person stated that on the morning of the accident, prior to 1100, he "topped off" both the accident helicopter and another helicopter owned by the operator. He stated that he was "absolutely" certain that he fueled them with 100 low lead aviation gasoline. He described the location and separation of the 100 low lead fuel hose and the jet fuel hose that were mounted on the fuel truck. After the fueling of the accident helicopter, it was initially flown by a pilot (previous pilot) who was not involved in the accident. The previous pilot, who is a certified flight instructor and has accumulated about 2,800 hours of total rotorcraft flight time, stated (interview synopses attached) that he had difficulty starting the helicopter on the morning of the accident. He stated that the engine was "flooded" so he "pulled the mixture out and leaned it." The helicopter was then able to be easily started, and it operated normally up until the time of the accident. The previous pilot also stated that he flew the helicopter from Felts Field to a local fairground for about 22 minutes at an altitude between 1,200 feet and 1,500 feet above the ground. After arriving at the fairground, he did not shut the engine down, nor was the engine shut down at any time during the day until the accident. The previous pilot stated that he flew about "eight to ten" sightseeing flights during the event. About six flights involved carrying one passenger, and two more involved carrying two passengers. Each flight was between five and seven minutes in length, and each involved picking up the helicopter, transitioning to climbing flight to about 1,000 feet above the ground, flying a "large oval" pattern, and then hovering to a landing. The previous pilot stated that the helicopter had not been refueled after its initial fueling earlier in the day at Felts Field. He stated that he did not check the fuel tanks with the dip stick, but he did remember that the fuel quantity gauge indicated he had between 1/4 and 1/2 tank of fuel during his last flight. He then got out of the helicopter, left its engine running, and flew the operator's other helicopter back to Felts Field. The accident pilot exchanged helicopters with the previous pilot at this time. The accident pilot stated (interview synopsis attached) that she and the previous pilot gave "about five or six rides apiece." She stated that she "didn't want to trade helicopters in the beginning of the day, but then [the previous pilot] decided to fly back home because things weren't that busy at the fair." The accident occurred during the accident pilot's first flight in the helicopter. She stated that the passenger weighed "about 270 pounds" and wanted to bring his girlfriend. The accident pilot stated that she would not allow the girlfriend on board because of weight concerns. After performing a run-up, the accident pilot and the passenger began the ride. She stated that the helicopter "felt real heavy" just after she "picked up" and began to climb up over trees. She stated that the engine suddenly "cut out" about 80 to 100 feet above the ground. The rotor revolutions per minute (RPM) gauge was "in the bottom of the green" and the fuel quantity gage was indicating "over 1/2 tank." The accident pilot stated that she force landed the helicopter and then waited for the blades to stop turning. The helicopter struck trees and was substantially damaged. PERSONNEL INFORMATION The accident pilot, age 34, held a Federal Aviation Administration (FAA) Commercial Pilot Certificate with ratings for airplane single-engine land, helicopter, and instrument airplane. According to FAA records, she was issued an FAA Second Class Medical Certificate on June 25, 1996, with the limitation that she "must wear lenses for distant [vision] - posses glasses for near vision." She reported that she had a total of 134 hours of helicopter flight time, including 26 hours in type. AIRCRAFT INFORMATION The aircraft, a 1976 Enstrom model F-28C helicopter, had been owned, operated and maintained by Custom Aviation, Inc. The helicopter is powered by a single turbocharged, fuel-injected Lycoming model HIO-360-C1A engine, which drives three main rotor blades and two tail rotor blades. According to the helicopter's maintenance log books (excerpts attached), the helicopter underwent an annual inspection on May 18, 1996, and a 50-hour inspection on July 30, 1996, with no discrepancies noted. The helicopter had accumulated 53.2 hours of flight time since the 50-hour inspection. According to the helicopter's engine log books (excerpts attached), the engine underwent a 100-hour inspection on August 23, 1996, and a 50-hour inspection on July 30, 1996, with no discrepancies noted. One entry, also dated July 30, stated: "removed and installed serviceable boost pump...." Another entry, dated three days prior, stated: "Installed rebuilt and [zero] timed fuel control servo [in accordance with] Lycoming [maintenance] manual. Flow checked & cleaned fuel injectors, cleaned tanks, cleaned fuel strainer, checked injector lines and spider diaphragm.... Ops and leaked checked good." The accident aircraft's fuel system consists of two interconnected 20 US gallon fuel tanks, which feed simultaneously to the engine. The tanks are located on the left and right side of the aircraft over the engine compartment. The tanks have a total fuel capacity of 40 US gallons, with a total of two gallons unusable fuel, one gallon unusable fuel in each tank. Each tank is gravity fed to a central distributing line which connects to the electric auxiliary boost pump and an engine driven pump. The fuel control valve is an "on-off" type and is located on the firewall next to the pilot's left shoulder. The fuel quantity gauge continuously indicates the total quantity of fuel. It is hooked up through a liquidometer float located in the right-hand fuel tank. A translucent strip on each tank provides a direct, visual indication of fuel level while the helicopter is on the ground. The Safety Board obtained aircraft fuel performance data from the aircraft manufacturer in an attempt to estimate the total amount of fuel consumed by the accident helicopter after it had been refueled up to the time of the engine failure. According to the data (computations attached), the helicopter would have conservatively consumed 27.4 gallons of fuel under the conditions at which is was being operated, leaving 12.6 gallons of capacity remaining. According to the operator, the helicopter was not insured for hull loss at the time of the accident. WRECKAGE AND IMPACT INFORMATION The wreckage was examined at the accident site by an FAA aviation safety inspector from Spokane. The inspector arrived about two hours after the accident. According to the inspector, a piece of wreckage was found near the initial impact point about 75 feet from the final resting site of the fuselage; this piece was identified as the tail rotor drive shaft. The stabilator, a tail rotor blade, and the tail boom were separated from the fuselage and were found distributed between the tail rotor drive shaft and the fuselage. About four inches of fuel depth was noted in the right half of the fuel tank, and about ten inches was noted in the left half of the tank. Six quarts of oil were found in the engine. The fuselage of the helicopter was leaning toward the left about 20 degrees from an axis perpendicular to the horizon. The left skid had been bent outward. All three main rotor blades remained attached to their hub. One of the blades was not damaged. Another blade received minor leading edge damage. The third blade had been bent forward and was twisted. The cockpit had been secured and the radios had been removed. The Safety Board authorized the operator to remove the wreckage on the evening of the accident and secure it in his facility for further examination. On October 7, 1996, FAA inspectors observed the operation of the engine, which had remained attached to the helicopter. The engine was able to be started and run up at an idle RPM. According to the inspectors, the rotor blades had been disengaged from the engine, and the engine was operated for a short period of time at idle speeds and with observed roughness. During the engine run-up test event, the operator suggested that the fuel in the helicopter had an odor that was similar to jet fuel. The FAA inspectors agreed. The operator volunteered to take fuel samples from the helicopter and have them analyzed at a laboratory in Seattle. An FAA inspector drained and measured the remaining fuel out of the wreckage; about 8.5 gallons of liquid were drained. Also, the Safety Board ascertained through interviews (synopses attached) that about 4.5 gallons of liquid had been drained out of the helicopter by the owner of a petroleum distributor, and about one additional gallon was drained out for smaller samples taken by an insurance adjuster, the FAA, and the operator. Based on this information, the Safety Board estimated that about 14 gallons of fuel would have remained in the helicopter at the time of the accident. However, according to the fuel consumption data previously mentioned (computations attached), only 12.6 gallons of capacity would have remained in the helicopter at the time of the accident. TESTS AND RESEARCH Operator's Sampling of Fuel. The operator stated that he drew samples of fuel from the accident helicopter, his other helicopter, all of his fixed-wing aircraft, his fuel truck, his above-ground fuel tank, and his mobile pick-up truck tank, one day after the accident. The samples were not controlled by, nor ever in the custody of, the FAA or the Safety Board. The operator stated that he brought the samples to Saybolt, Inc., in Seattle, Washington, for analysis. On October 14, 1996, he received the results from Saybolt and notified the FAA and the Safety Board that jet fuel contamination was found in the samples. The operator stated that he received a shipment (copy of invoice attached) containing 2,325 gallons of 100 low lead aviation fuel into his above-ground tank on September 23, 1997, from a local petroleum distributor. He stated that he suspected that the shipment was contaminated, and he notified the owners of about 36 airplanes (listing attached) that had been fueled by the operator since September 23, 1997, of the contamination. The Safety Board interviewed (interview synopses attached) those persons involved in the operator's sampling of fuel. One employee stated that he was asked by the operator to obtain fuel samples on the morning of October 6, one day after the accident. The employee stated that he first sampled the operator's four fixed-wing aircraft. He stated that another employee was asked to sample the operator's helicopters. The employee then went to the large above-ground fuel tanks and obtained a sample of jet fuel and a sample of 100 low lead aviation fuel. He stated that the fuel "seemed to come out like it usually does," and he did not notice anything unusual. He did not make any entries on the metering sheets (copies attached) when he took the samples. He distinctly remembered taking the samples, and that it took about 30 minutes. After he took the samples, he placed them in a box, brought the box into the operator's shop, and placed the box on a shelf where they were "non-conspicuous." The employee also stated that he flew in one of the operator's Cessna 172s for about six hours on the day of the accident. The Cessna had been fueled by the operator's fuel truck on the day preceding the accident, and again on the day of the accident. The employee reported that there were "no problems" with the Cessna during the time that he flew it. The operator's mechanic stated that he obtained a sample from the accident helicopter on the morning following the accident. He remembered that he obtained a sample from one of the tanks by pulling the tank drain off, and he obtained a sample from the other tank by draining fuel from its strainer. The mechanic also stated that he was "pretty sure" he also pulled a sample from the operator's other helicopter "... a day and a half later " in the hangar. After obtaining the samples, the mechanic labeled the jars, including date and time, and gave them to the operator. Another employee stated that he remembered taking fuel samples, but he could not remember exactly from where. He stated: "I think I took samples from the main [above-ground] tank... but I can't remember." He also stated that he may have taken a sample from the mobile pick-up truck external fuel tank that was at the accident site, but again he could not be sure. He stated that he took the samples about 1230 on October 6, 1996, because he was asked to perform the sampling when he first started his shift. He stated that he could not remember for sure who had asked him to take the samples, and he did not remember having any conversations about the helicopter accident around the time of the sampling. Results from Operator's Fuel Tests. According to the data sheets (attached) from Saybolt, Inc., of the operator's fuel sample testing, the following results were found: LABELED AS: ALLEGED SOURCE: RESULT: N-9248 Operator's Other Helicopter Contaminated N-7275J Operator's Airplane Not Contaminated N-3409J Operator's Airplane Not Contaminated Pete Wing Operator's Tank After New Fuel Lot Not Contaminated Tank; 10/06/96 Operator's Tank Before New Fuel Lot Contaminated N-4360L Operator's Airplane Not Contaminated N-69133 Operator's Airplane Not Contaminated Left Tank; 10/06/96 Accident Helicopter Contaminated Right Tank; 10/06/96 Accident Helicopter Contaminated Chevy Dually Operator's Pick-up Truck Tank Contaminated Fuel Truck; 10/06/96 Operator's Fuel Truck Before Purging Contaminated The Safety Board initially requested copies of the Saybolt testing from the operator. The operator provided only those test results that indicated fuel contamination. The Safety Board later obtained all of the sample results from Saybolt, and discovered that some of the tests indicated no contamination. When the operator was asked why his fixed wing airplane samples did not disclose evidence of contamination, the operator stated that he thought the samples were taken after the fuel was purged out of the tanks and newer fuel from a later shipment was placed in them. The Safety Board attempted to verify this through interviews (synopses attached). The interviews revealed that the fuel samples were taken one day after the accident by an employee of the operator prior to any purging, and that the fuel in the airplanes would have been representative of the fuel in the operator's above-ground tank which was suspected by the operator as being contaminated. Inspection of Above-Ground Fuel Pumps. The Safety Board contacted the company that sold and serviced the operator's above-ground fuel tank (interview synopsis attached). Service personnel, at the Safety Board's request, inspected the tank and pump after the accident. Service personnel reported that they found no anomalies and that there was "no common way to mix fuels" in the system. It was also noted that there are no junctions in the tanks or the plumbing between the Jet A and 100 low lead fuel supplies. Fuel Distributor Handling. The Safety Board contacted the owner (interview synopsis attached) of the petroleum distributor that delivered
a loss of engine power for undetermined reasons.
Source: NTSB Aviation Accident Database
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