Heber City, UT, USA
N280AD
ENSTROM 280FX
The operator was selling helicopter rides at a fly-in. After one such ride, a pilot, who was acting as a ground crewmember, measured the fuel level in the tanks with a calibrated wooden stick while the engine was running and the rotor blades were turning. He determined that about 8 gallons of fuel remained, which was sufficient for the next ride. About 9 minutes after takeoff, the engine lost power. Witnesses reported seeing the helicopter flying low when they heard the engine “sputter” or “pop.” The pilot reported that he performed an autorotation to a field; the helicopter landed hard on sloping terrain and rolled over onto its right side. Examination of the wreckage revealed that the engine lost power as a result of fuel exhaustion. Postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have prevented normal operation. The helicopter manufacturer provided a wooden stick for pilots to dip a fuel tank during preflight to determine the total quantity of fuel available for flight. 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 lower levels. It is likely that the pilot who checked the fuel level before the accident flight did not accurately determine the amount of fuel in the tanks. The helicopter was equipped with a fuel gauge mounted on the instrument panel in the cockpit that would have provided the accident pilot with a direct reading of the helicopter’s fuel quantity. The helicopter was being flown with the two cabin doors removed, an approved operation according to the rotorcraft flight manual. The helicopter left the factory with individual seat belts and shoulder restraints for three occupants. The passenger reported that someone buckled her and her son into the same lap belt; no shoulder strap was used. During postaccident examination, it was noted that the buckle half of the lap belt for the center seat had been removed. The center seat single-strap shoulder harness was found attached to the buckle half of the right seat lap belt. The right seat Y-type shoulder harness was found stowed behind the right seat back cushion. The first responders found the right seat occupant under the helicopter with his legs still in the cabin. Both passengers sustained serious injuries. It is likely that the lack of separate lap belt/shoulder harness assemblies for the two passengers increased the severity of their injuries.
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 Fahrenheit, the density altitude was calculated to be 8,003 feet. WRECKAGE AND IMPACT INFORMATION The helicopter was found on grass covered sloping terrain, in a residential development. There was no evidence of fire. The helicopter was resting on its right side and aligned in a westerly direction. The landing skids had numerous fractures and failures and were folded to the left about 80 degrees. The bottom/belly of the cabin and engine compartment was significantly crushed and deformed. All the windows were broken from the cabin, and the doors were not with the wreckage. The cabin seat deck/structure exhibited significant crushing consistent with a fairly-level near-vertical impact. The pilot’s (left side) flight controls were in place and the secondary (right side) flight controls were not installed. There were four lap belt attachment points on the cabin's aft bulkhead just above the seat pan;far left, center left, center right, and far right. There were three shoulder harness inertia reels mounted on the cabin’s aft bulkhead, one for each occupant. The left and right seat positions were equipped with Y-type two-strap harnesses, and the center seat position was equipped with a single-strap harness. Two piece lap belts were installed for the right and left seat occupants. The single-strap harness for the center seat occupant, which was similar to the combined seat belt/shoulder harness unit found in many automobiles, was secured at one end to the inertia reel and at the other end to the center right lap belt attachment point, and a metal tongue was threaded onto the strap. The metal tongue on the single strap was supposed to be inserted into a buckle on a short strap that should have been attached to the center left lap belt attachment point. However, the buckle part of the center seat belt/shoulder harness unit was not installed. The left (pilot’s) shoulder harness and lap belt were found unbuckled. The center seat single-strap shoulder harness was found attached to the buckle half of the right seat lap belt. The first responders found the right seat 14-year-old male under the helicopter with his legs still in the cabin. He suffered numerous fractures, brain and torso hematomas, and severe internal injuries. His mother, in the center seat, had her left foot nearly severed and sustained several spinal compression fractures. The straps of the buckle half of the right seat lap belt and the single-strap shoulder harness had been cut by first responders in multiple places. The main rotor blades remained attached to the rotor head and appeared to be bent upwards. The tail cone was still attached to the cabin/fuselage and exhibited denting and wrinkling. The right horizontal stabilizer was folded down, and the left one exhibited no damage. The two 21-gallon fuel tanks had shifted, but appeared undamaged except for a minor dent in the left tank. A first responder reported seeing fuel dripping from the helicopter. On September 8, 2011, a team of investigators, consisting of an NTSB investigator, an FAA inspector, a representative from the engine manufacturer, and a representative from the helicopter manufacturer, assembled at Heber City Airport to examine the wreckage. Examination of the engine found that the cooling fan had some damaged blades, and one of the blades had been forced through the fan shroud, indicating that the engine was not running at impact. The crankshaft was rotated by hand, and rotational continuity was established throughout the engine and valve train. Thumb compression was noted on all four cylinders. The cylinders were borescope inspected, and no anomalies were noted. The dual magneto was rotated by hand and produced spark at all leads. The fuel servo exhibited no signs of visual damage. Its inlet screen was found free of debris, and no fuel was present. The fuel flow divider was found free of debris, and no fuel was noted. The gascolator was opened, and it contained about 2.2 fluid ounces of fuel. No evidence of any pre-impact mechanical discrepancies that would have prevented normal operation was found with the helicopter’s airframe or engine. TESTS AND RESEARCH The caution/warning annunciator panel was removed from the helicopter and sent to the NTSB’s Materials Laboratory in Washington, D.C. Examination of the unit revealed that none of the light bulbs exhibited stretched filaments. However, it is possible that the vertical loads during the impact sequence were insufficient to stretch the filaments.
The pilot’s failure to ensure that there was sufficient fuel onboard to conduct the flight, which resulted in a loss of engine power due to fuel exhaustion. Contributing to the severity of the passengers’ injuries was the operator’s failure to provide adequate restraints for the passengers.
Source: NTSB Aviation Accident Database
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