SEA97FA003

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