Introduction
On May 22, 2009, about 1330 mountain standard time, an experimental homebuilt Gauchat Safari helicopter, registration N147MD, impacted terrain near Rock Springs, Arizona, following the in-flight separation of both main rotor blades. The private pilot and one passenger sustained fatal injuries. The helicopter was substantially damaged by impact forces and a post-crash fire. Visual meteorological conditions prevailed, and no flight plan was filed.
History of Flight
The local personal flight departed Rock Springs about 1325 with a planned destination of Phoenix, Arizona. Witnesses reported that the helicopter had just departed from a parking lot approximately 0.3 nautical miles north of the accident site. They observed the helicopter flying southbound parallel to highway 17 when one of the main rotor blades separated. The helicopter then fell to the ground.
Personnel and Aircraft Information
The pilot held a private pilot certificate but no personal flight records were located. According to FAA medical records, the pilot reported on May 5, 2008, a total flight time of 270 hours, with 50 hours logged in the preceding 6 months. The helicopter, an experimental homebuilt Gauchat Safari, serial number 2129, was issued a special airworthiness certificate on May 30, 2006. Its logbooks indicated a total airframe time of 237.3 hours at the last conditional inspection on May 10, 2009.
Wreckage and Impact Information
An FAA inspector responded to the scene. The accident site comprised the fuselage, tailboom, and tail rotor system. Debris included both main rotor blades: one located 620 feet northwest of the main wreckage, and the second 300 feet east. A push-pull control tube was found 170 feet northwest, and an operating handheld GPS unit was located 100 feet northwest of the main wreckage.
Medical and Pathological Findings
The Maricopa County Coroner performed an autopsy on the pilot on May 26, 2009, determining the cause of death as blunt force injuries. Toxicological testing by the FAA Civil Aerospace Medical Institute found no carbon monoxide, cyanide, or volatiles. However, doxylamine was detected in blood at 0.101 ug/ml and in the liver.
Tests and Research
Investigators examined the wreckage at Air Transport, Phoenix, on June 29, 2009, and August 14, 2010. Components of the main rotor head were sent to the NTSB materials laboratory. The materials specialist determined that the main rotor head spindle had failed in fatigue, with initiation at machining marks located at a radius at the intersection of the bearing diameter with the larger inboard diameter, normally obscured by the grip nut.
Additional Information
Following the accident and investigation, the manufacturer issued mandatory inspection bulletin MI-002, requiring inspection of the main rotor spindle for distinct machining marks of irregular depth. The bulletin also specified that spindles subjected to shock loads, such as from accidents, clutch re-engagement with rotor blades in motion, hard engine starts, over-torque of the castle nut, or repeated overspeed of the main rotor head, should be inspected. According to FAA Advisory Circular AC 20-27F, amateur builders are free to develop their own designs or build from existing designs, and the FAA does not approve these designs or develop design standards for the wide variety of configurations.