Aviation Accident Summaries

Aviation Accident Summary CEN13LA507

Clayton, NM, USA

Aircraft #1

N744KA

Robinson Helicopter Company R44 II

Analysis

The pilot reported that 25-30 minutes into the aerial photography flight, the helicopter began to settle (descend under power) while established in a left turn from an easterly heading about 100 feet above the ground. The pilot increased collective control, but the helicopter continued to descend as it approached two sets of power lines. He stated that with full engine power, the helicopter was able to clear both sets of power lines; however, the low rotor speed warning horn sounded as the helicopter crossed over the second set of power lines. The pilot briefly reduced the collective control to regain rotor speed, but, as the helicopter approached the ground, he increased collective control in another attempt to arrest the descent. The pilot stated that the helicopter impacted terrain in a manner similar to a hard landing, bounced, and rolled over onto its left side. The pilot reported there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. In his statement, the pilot indicated the likelihood that the helicopters encounter with a southerly wind gust during the left turn from an easterly heading sufficiently reduced the amount of available lift from the main rotor to allow the helicopter to descend with full engine power and collective control. A nearby weather station reported gusty wind conditions from the south, with peak speeds of 32 knots. A southerly wind gust during a left turn from an easterly heading would have resulted in a tailwind condition and an associated loss of available lift from the main rotor. The pilot estimated the helicopters weight at the time of the accident was about 9 pounds below the helicopters certificated maximum gross weight. The pilots maneuvering of the helicopter at a low altitude, while at nearly maximum gross weight, reduced his ability to regain vertical control before the helicopter encountered the power lines and terrain.

Factual Information

On August 26, 2013, at 1525 mountain daylight time, a Robinson Helicopter Company model R44 II helicopter, N744KA, was substantially damaged while maneuvering near Clayton, New Mexico. The commercial pilot was not injured. The 3 passengers sustained minor injuries. The airplane was registered to and operated by King Ag Leasing, under the provisions of 14 Code of Federal Regulations Part 91, without a flight plan. Day visual meteorological conditions prevailed for the personal flight, which departed Clayton Municipal Airpark (KCAO), Clayton, New Mexico, at 1450.The pilot reported that the purpose of the flight was to conduct aerial photography of a nearby location where the passengers had recently hunted. The pilot reported that he was concerned with the density altitude at the departure airport, so he initially loaded only two passengers and completed a takeoff and landing. The helicopter reportedly had no performance issues during the short flight and a third passenger subsequently boarded the helicopter. After an uneventful takeoff, the flight proceeded north of the airport toward the location to be photographed. The pilot reported that 25-30 minutes into the flight, the helicopter began to settle (descend under power) while established in a left turn from an easterly heading about 100 feet above the ground. The pilot increased collective control, but the helicopter continued to descend as it approached two sets of power lines. He stated that with full engine power the helicopter was able to clear both sets of power lines; however, the low rotor speed warning horn sounded as the helicopter crossed over the second set of power lines. The pilot briefly reduced the collective control to regain rotor speed, but as the helicopter approached the ground he increased collective control in another attempt to arrest the descent. The pilot stated that the helicopter impacted terrain in a manner similar to a hard landing, bounced, and rolled over onto its left side. The pilot reported there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The pilot stated that the helicopter likely encountered a southerly wind gust during the left turn from an easterly heading, which reduced the amount of available lift from the main rotor enough to allow the helicopter to descend with full engine power and collective control. Additionally, the pilot estimated the helicopters weight at the time of the accident was about 2,391 pounds. The helicopters certificated maximum gross weight was 2,400 pounds. The nearest aviation weather reporting station was located at Clayton Municipal Airpark (KCAO), Clayton, New Mexico, about 12 miles south of the accident site. At 1555, the KCAO automated surface observing system reported: wind from 160 degrees at 17 knots, gusting 32 knots; visibility 10 miles; broken ceiling at 8,000 feet above ground level; temperature 31 degrees Celsius; dew point 11 degrees Celsius; and an altimeter setting of 30.22 inches of mercury. At 1553, a peak wind was reported from 170 degrees at 32 knots. The weather station elevation was 4,964 feet mean sea level. The calculated density altitude was 7,721 feet.

Probable Cause and Findings

The pilots loss of vertical control after the helicopter encountered a gusty tailwind while maneuvering at a low altitude and near the helicopters maximum gross weight.

 

Source: NTSB Aviation Accident Database

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