DEN00LA113
DEN00LA113

On June 17, 2000, approximately 1500 mountain daylight time, an Enstrom 280CB helicopter, N440RB, was substantially damaged following an autorotation near Sierra Blanca Regional Airport, Ruidoso, New Mexico. The commercial pilot and his two passengers received minor injuries. The pilot was operating the helicopter under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local sightseeing flight that originated approximately 20 minutes before the accident. No flight plan had been filed.

The pilot said, in a telephone interview, he departed (with full fuel tanks) El Paso, Texas, and flew approximately 2 hours to Ruidoso, New Mexico. His plan was to give helicopter sightseeing rides to people at a local fair. The pilot's ground support partner was planning to intermittently fuel the aircraft's right saddle tank with 5 gallon cans to maintain a 25% fuel load. The pilot said that he or his partner would "stick the two tanks" at regular intervals to determine the fuel quantity. The aircraft manufacturer made the fuel measuring stick, and it read 10 gallons, 20 gallons, and Full. If you measure one tank, the stick's calibration reads total fuel (assuming that that aircraft is level and that the fuel levels are in homeostasis). Neither the pilot nor the ground support partner could remember how much fuel had been put in the right fuel tank or when both tanks were last "sticked."

The pilot said that the first three rides were approximately 3 to 6 minutes in length. On the next ride (the 5th flight for the day), the passengers requested to be flown over their house, which was located approximately 14 nautical miles from the takeoff point. When the pilot returned from that flight, two more people from the same family requested the same residence flyby. The pilot could not remember if the helicopter was serviced during the passenger change. During the return flight, his ground support partner asked the pilot by radio if he would need fuel when he landed; he responded that he would.

The pilot said that as he approached the airport in cruise flight, he began having a problem with the engine. He said that the power continued to deteriorate, and he began to look for an emergency-landing site. Because of transmission wires and trees, he had to stretch his autorotation to reach the selected site. The pilot said that he felt the helicopter's sink rate increase, but had insufficient main rotor RPM to slow the descent rate. The helicopter impacted the ground hard and "spun 180 degrees opposite from the direction of flight." During the landing sequence, the main rotor blades cut off the tail boom and slapped the ground. The left skid supports were broken and the helicopter came to rest leaning on its left side.

The pilot said that before the helicopter was recovered, he "sticked" the left tank and it indicated that there were 9 gallons remaining. It was not determined if there was any fuel in the right tank; the interconnect line would have permitted fuel to flow from the right tank to the left tank. The pilot further stated that while the helicopter was being transported, an undetermined amount of fuel was observed dripping onto the road.

The aircraft manufacturer's representative stated that if the aircraft were leaning to one side, any fuel measurement made with the stick would be unreliable. He said that in the above scenario, the actual fuel amount could have been as low as 2 to 4 gallons.

The same representative said that the two 21 gallon (20 gallons usable) fuel tanks do have a 3/8 inch in diameter interconnecting line, but it is recommended that refueling be done through the fueling caps in each tank. He said that if the fuel is put in on one side, it is unknown how long it would take for the tanks to equalize, particularly if the engine was being operated at or near full power. The interconnecting line has a "T" connector in it with a 3/8 inch in diameter main fuel line leading to the engine. The manufacturer's representative said that if the helicopter was refueled on one side while the engine was running, that it was possible (at low fuel levels) for the other fuel tank to suck air (cavitate). He also said that the fuel gauge indication is derived from a single fuel level float device that is located in the right fuel tank.

At 1511, the weather conditions at Sierra Blanca Regional Airport (elevation 6,811 feet), Ruidoso, New Mexico, were as follows: temperature 72 degrees Fahrenheit (22 degrees Centigrade); dew point 52 degrees Fahrenheit; altimeter setting 30.17 inches of mercury. The density altitude was 9,012 feet.

The aircraft's manufacturer estimated that under these flight conditions, fuel consumption could be as high as 18 to 22 gals per hour. The helicopter was taken to Dallas, Texas, where maintenance personnel test ran the engine (in the helicopter). At first the engine would not start; fuel was added to the two tanks, and the engine subsequently ran with no abnormalities noted. The maintenance personnel also examined the Sprague clutch; it was found to free wheel easily, to engage and disengage with no difficulty, and showed no signatures of having been over heated.

The pilot said that he registered the helicopter on May 24, 2000, and he estimated that he had a total of 25 to 27 hours in make and model.

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