Albuquerque, NM, USA
N7026J
ROBINSON HELICOPTER R22 BETA
The commercial pilot was practicing pinnacle approaches in the helicopter. The pilot reported that, during the second practice approach, the helicopter gradually slowed, and, when it was about 15 ft above the ground and between 20 and 25 knots, the low-rotor rpm horn sounded. The pilot attempted to increase the rotor rpm by lowering the collective and applying aft cyclic, but the helicopter continued to descend, and the pilot subsequently performed an autorotation. During the landing, the left skid struck a hill, and the helicopter rolled on its side. A postaccident examination of the helicopter did not reveal any preimpact anomalies. The helicopter was operating at a density altitude of about 7,000 ft, and the pilot reported that the helicopter felt "heavy," likely because the main fuel tank was filled instead of the auxiliary fuel tank before the flight. The combined effects of the helicopter's high weight and the high-density altitude reduced the helicopter's performance and limited the power available, which made it critical for the pilot to maintain rotor rpm while executing the approach.
On September 26, 2014, about 0745 mountain daylight time, a Robinson R22 Beta helicopter, N7026J, sustained substantial damage when it impacted the ground and rolled over during landing. The pilot was not injured and the passenger received minor injuries. The aircraft was registered to Redhills Corp and operated by Vertical Limit Aviation, LLC., under the provisions of 14 Code of Federal Regulations Part 91 as personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The local flight originated from the Double Eagle II Airport, Albuquerque, New Mexico, about 20 minutes prior to the accident.The pilot reported that he was making a second practice approach to a pinnacle in the helicopter when the mishap occurred. The helicopter was slowing gradually and when it was about 15 feet above the ground and 20- 25 knots forward speed, the low rotor RPM horn sounded. The pilot attempted lowering collective and pulling "gentle" aft cyclic to increase rotor RPM and turned to egress the area. The helicopter continued to descend and the pilot executed an autorotation. During the landing, the left skid struck a hill and the helicopter rolled over on its side. The pilot did not report any mechanical anomalies with regard to the operation of the helicopter. According to the pilot's statement, before the flight he had asked that the auxiliary fuel tank be filled, but line service personnel instead filled the main fuel tank. Upon initiating the flight, the pilot noted that the helicopter was "heavy". According to the Federal Aviation Administration Rotorcraft Flying Handbook, FAA-H-8083, certain conditions of high weight, high temperature, or high density altitude, can result in a situation where rotor RPM is low even when using maximum throttle. It further stated that this usually results from the main rotor blades having an angle of attack that has created so much drag that engine power is not sufficient to maintain or attain normal operating RPM. According to Google Earth and the accident location provided by the pilot, the ground elevation was determined to be about 5,900 feet above mean sea level. The density altitude was calculated to be about 7,000 feet, based on this elevation and the weather conditions reported at the departure airport. A postaccident examination of the helicopter did not reveal any pre-impact anomalies.
The pilot's failure to maintain main rotor rpm during a pinnacle approach, which resulted in a loss of helicopter control and collision with terrain. Contributing to the accident was the pilot's decision to attempt the approach given the helicopter's weight and the high-density altitude.
Source: NTSB Aviation Accident Database
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