Monday, August 28, 2017

Robinson R44 II, N61NM, registered to A M Helicopter Services LLC and operated by a private individual: Accident occurred August 22, 2017 in El Dorado County, California

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Helena, Montana
Robinson Helicopter Company; Torrance, California 

Aviation Accident Preliminary Report - National Transportation Safety Board:

A M Helicopter Services LLC:

NTSB Identification: WPR17LA188
14 CFR Part 91: General Aviation
Accident occurred Friday, August 25, 2017 in El Dorado Hills, CA
Aircraft: ROBINSON HELICOPTER COMPANY R44 II, registration: N61NM
Injuries: 2 Minor.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On August 25, 2017, about 1900 Pacific daylight time, a Robinson R-44 Raven II, N61NM, was substantially damaged when it encountered a dynamic rollover during a forced landing attempt in Eldorado Hills, California. The commercial pilot and passenger received minor injuries. The helicopter was registered to A M Helicopter Services, LLC and operated by a private individual as a personal flight, which was conducted under the provision of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and a flight plan was not filed for the local flight that departed Auburn Municipal Airport (AUN), Auburn, CA at 1830.

According to the accident pilot and his passenger, who was an airframe and powerplant mechanic, the purpose of the accident flight was to complete a functional flight of the helicopter as it had recently been leased by a flight school. Prior to departure, the pilot flew the helicopter once in the airport traffic pattern and then taxied to the fuel isle. After adding 20 gallons of 100 low lead aviation grade gasoline, the pilot and his passenger departed on the accident flight. They flew around a soccer field so the passenger could take photographs and then flew to a nearby lake where they completed an autorotation. During the end of the maneuver, as they approached the ground both the pilot and passenger heard the low rotor rpm horn, which was accompanied by its corresponding annunciator light. The rotor rpm increased after the pilot added power. They subsequently flew to a friend's house and approached the property from the north. The pilot decelerated and transitioned into an in-ground effect hover over his friend's backyard, but the downwash started to blow debris into the pool. Although his friend was signaling the pilot to land on a concrete block adjacent to the pool, the pilot elected to find another landing zone. He backed the helicopter up over a solar panel array at a lower terrain elevation, but the main rotor rpm started to decay and the low rotor rpm horn engaged. The pilot applied full power, which increased the manifold pressure to 28 in Hg and placed the rotor rpm at approximately 96%; however, the helicopter started to descend, so the pilot lowered the collective, which returned the rotor rpm to the normal range. He then completed a pedal turn and rotated the helicopter about 360° to look for a more suitable landing site, but the helicopter started sinking again. The pilot informed his passenger that he was going to set the helicopter down on the solar panel array. As the left skid impacted a solar panel, the passenger exited the left side of the helicopter and ran to the east. Almost simultaneously, the helicopter ascended about 20 feet and then began to sink again, but as it descended the helicopter followed the passenger to a grass area. The helicopter's right skid impacted the grass followed by the left skid and the helicopter rollover onto its left side. 

In a subsequent interview, the passenger stated that he did not hear an engine or rotor harmonic during the dynamic rollover. 

A postaccident examination of the helicopter by the Federal Aviation Administration and NTSB revealed substantial damage to the main rotor blades and cockpit. Mechanical continuity was confirmed from the cyclic to the swash plate, the collective to the main rotor blades, and from the rudder to the tail rotor.

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