N280AD

HISTORY OF FLIGHT

On September 3, 2011, about 1215 mountain daylight time, an Enstrom 280FX helicopter, N280AD, was substantially damaged during impact with terrain following a loss of engine power near Heber City, Utah. The commercial pilot and two passengers were seriously injured. High Velocity Aviation was operating the helicopter under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the local air-tour flight, which had originated from Heber City Municipal Airport approximately 9 minutes before the accident. A flight plan had not been filed.

The Heber Valley Chapter of the Experimental Aircraft Association (EAA) was holding a Heber Valley Fly-In, and High Velocity Aviation was selling helicopter rides at the fly-in. The first pilot to give rides in the helicopter on the day of the accident said that he performed a preflight inspection of the helicopter, which included removing the right-hand set of flight controls and measuring the fuel level in the tanks with a wooden calibrated stick. He determined that there were 29 to 30 gallons of fuel onboard. He said the tour flights were 2, 6, or 12 minutes in duration. The first pilot said that at 0955, he departed and flew several air tours over the next 40 minutes; he added that the passengers were exchanged with the engine running and the rotor blades were turning. When he landed, the owner and the accident pilot added 10 more gallons of fuel to the tanks. He flew a few more rides and then exchanged places with the accident pilot.

The accident pilot flew for several rides while the owner and the first pilot loaded passengers and explained to them how to use their seatbelts. About 1200, when the helicopter landed from a tour, the first pilot measured the fuel level in the tanks with the wooden stick, while the engine was running and the rotor blades were turning. He determined that there were approximately 8 gallons of fuel remaining. He then informed the accident pilot of his fuel status and told him that his next tour was for 12 minutes. The first pilot waved to the owner to bring over the next two passengers, a mother and her 14-year-old son.

The mother was seated in the center of the helicopter’s bench seat between the pilot and her son. The mother reported that she and her son were given headphones, but she was not told how to use them. She said she did not receive a briefing about their use, and she reported having great difficulty communicating with the pilot and her son throughout the flight. Additionally, she was not briefed about the seat belts. Someone buckled her into her seat with her son; that is, they shared the same lap belt. Vertically between them was a single-strap shoulder harness, which connected to their lap belt. Neither she nor her son had a shoulder strap across their chest.

The accident pilot reported that he departed on the air tour at 1200. He flew east to view some property that the passengers wanted to see. About 9 minutes after takeoff, as he was flying west returning to the airport, he heard and felt a change in the engine operation. He saw an open field on his left, and he performed a turning 180-degree autorotation towards the field, which also provided an easterly headwind for the emergency landing.

Several witnesses reported that they saw the helicopter flying west low over the valley. Suddenly, many of them heard the engine “sputter” or “pop,” and the “props” [main rotor blades] slowed down and appeared to be “stalling.” Several said the engine sounded like it lost rpm, and one witness said it sounded like the engine was running out of gas. Several witnesses said the helicopter’s nose dropped 20 to 30 degrees or more, as the helicopter spun or turned to the left. The helicopter descended rapidly and continued turning until ground impact. It came to rest on its right side facing west.

PERSONNEL INFORMATION

The pilot held a commercial license with helicopter, airplane single land and sea, airplane multiengine land, and instrument ratings. He also held a flight instructor certificate with helicopter, airplane and instrument ratings. His most recent second-class Federal Aviation Administration (FAA) medical certificate was issued on August 3, 2011. The pilot reported that he had a total of 2,363 hours of flight experience, with 150 hours of helicopter flight time. He reported having 46 hours total flying experience in an Enstrom 280FX, with 7 hours in the last 90 days.

AIRCRAFT INFORMATION

The single engine helicopter was manufactured in 1987 by the Enstrom Helicopter Corporation. It was equipped with a three-bladed main rotor, a two-bladed tail rotor, and a skid-type landing gear. The helicopter had a maximum lifting capability of 2,600 pounds and a useful load capacity of about 1,030 pounds. The helicopter was powered by a Lycoming HIO-360-F1AD four cylinder, horizontally opposed, fuel injected, turbocharged, air cooled engine. This engine was designed to produce 225 horsepower up to 12,000 feet density altitude. The last required annual inspection was performed on August 15, 2011; the helicopter had 1,180 flight hours on it at the time of the accident.

The helicopter was equipped with two interconnected 21 US gallon fuel tanks, which fed simultaneously to the engine. They were located on the left and right sides of the aircraft and directly over the engine compartment. The fuel interconnect plumbing permitted the fuel level to equalize in both tanks, thus permitting refueling of both tanks from one side. Each tank had 1 gallon of unusable fuel, resulting in a total usable fuel quantity of 40 gallons. A fuel quantity float indicator was located in the right fuel tank and provided fuel-available information continuously to the pilot in the cockpit via a fuel quantity gauge, which read in pounds of fuel.

The helicopter manufacturer provided a 20.25-inch-long wooden stick for pilots to dip, or stick, a fuel tank during preflight to get the total quantity of fuel available for flight. The stick had calibration marks for full, half and one-quarter fuel levels. The stick provided a visual indication of the fuel level in the tanks, but it was not calibrated below the 1/4 fuel level of (10 gallons). A representative of the helicopter manufacturer stated that caution must be exercised when measuring fuel quantity with a stick, because the irregular shape of each fuel tank can make it difficult to interpret the actual fuel quantity at these lower levels. He pointed out that his company did not anticipate pilots routinely operating significantly below the 1/4 fuel level. He stated that it would be additionally challenging to measure the fuel level with a stick when the engine is running and the main rotor blade is turning overhead, because there is only about 34 inches of clearance between the fuel tank cap and the rotating blades.

The engine’s fuel consumption varies according to the type of flight operation being performed. The manufacturer’s Operator Manual and Rotorcraft Flight Manual indicated that at a constant 75% power and properly leaned, the engine will burn 14.7 gallons per hour (gph). The manufacturer provides a Direct Operating Cost information sheet to prospective buyers, which suggests that an operator should plan on using 16 gph of fuel. The first pilot reported that he planned fuel utilization at 15 gph. Another pilot, who had flown the helicopter several years earlier, stated that his experience indicated fuel burn rates of 16.6 to 18.5 gph.

A test pilot, employed by the helicopter manufacturer, performed a Hover-In-Ground-Effect (HIGE) test in February 2012, at the request of the National Transportation Safety Board’s (NTSB) investigator-in-charge (IIC). This airborne flight test involved no translational movement, only hovering. It lasted 25.5 minutes, with a fuel burn rate of approximately 23.5 gph. The NTSB IIC performed fuel burn calculations by using the recorded tachometer time from the beginning of the first air-tour to the accident (2.3 hours) and fuel information provided by the first pilot (39 to 40 gallons total). The results were 16.9 gph to 17.3 gph.

FAA regulations regarding fuel requirements for flight in visual flight rules (VFR) conditions (14 CFR 91.151) states, in part:

No person may begin a flight in a rotorcraft under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed, to fly after that for at least 20 minutes.

The helicopter cabin was provided with two swing-open doors. The helicopter can be flown with either the left, the right or both doors removed; the doors were not installed on the helicopter at the time of the accident. The helicopter left the factory with individual seat belts and shoulder restraints for three occupants. The helicopter also left the factory with an intercom-communication system. This permitted clear communication between the pilot and both passengers. An annunciator panel, which contained all the warning and caution lights, was located at the top of the instrument panel in the center of the cockpit. This panel included warning lights for low rotor rpm, clutch disengagement, and low fuel pressure. The three caution lights included engine overboost, and main and tail rotor transmission chip lights. The main rotor system also had a loud horn, which sounded for low rotor rpm.

METEOROLOGICAL INFORMATION

At 1252, the reported weather conditions at Provo, Utah (PVU; elevation 4,497 feet), were: wind 150 degrees at 6 knots; visibility 10 statute miles; scattered cloud condition; temperature 75 degrees Fahrenheit; dew point 37 degrees Fahrenheit; altimeter setting 30.16 inches of mercury. The Provo airport is located 230 degrees for 23 nautical miles from the accident site. Using the elevation at the accident site, 6,090 feet, and a temperature of 70 degrees Fahrenh...