On July 18, 2006, at 1505 Hawaiian standard time, an amateur-built Hammack Air Command Elite gyrocopter, N6111A, collided with terrain after the pilot experienced a loss of control near Hilo International Airport, Hilo, Hawaii. The pilot/owner was operating the gyrocopter under the provisions of 14 CFR Part 91. The commercial pilot, the sole occupant, was seriously injured; the gyrocopter was destroyed. The personal local flight departed from Hilo about 10 minutes prior to the mishap. Visual meteorological conditions prevailed and a flight plan had not been filed. During a telephone interview with a National Transportation Safety Board investigator, the pilot stated that he departed runway 03. He continued toward the coastline and planned to return back to the airport to perform touch-and-go practice takeoffs and landings. After making an intended shallow right turn (toward the east) inland, while about 500 above ground level (agl), he attempted to maneuver the gyrocopter back to level flight and arrest the turn. The gyrocopter continued to turn and began a shallow descent. The pilot further stated that the gyrocopter increased the rate of turn and continued to lose altitude. At 100 feet agl he realized that a forced landing was imminent. The aircraft collided with terrain about 15 feet from the main road Kalanianaole, located north of the airport. The pilot constructed the gyrocopter and performed the maintenance on it regularly. He believed a pushrod had separated in the gyrocopter's controls. Over 2 to 3 years, the pilot had amassed 53 flight hours in the gyrocopter. A Federal Aviation Administration (FAA) inspector examined the wreckage several weeks after the accident occurred. He stated that a bolt attaching a control rod in the cyclic system was missing. He was unable to locate the bolt or its respective nut. A representative from Air Command International, Inc., the kit manufacturer, reviewed photographs taken by the FAA of the gyrocopter wreckage. He stated the separated piece appeared to be the heim joint (rod end) of the control tubes for the joystick (akin to a cyclic control). The representative reported that the heim joint was designed to be held in place by a nylon-locking (Nylock) nut and bolt system using a AN4-14A bolt, two AN4 washers, and a AN3625-428A ¼-inch lock nut. He noted that all the aforementioned hardware is included with the kit. The representative further stated that the Nylock nut ensured a secure joint assembly upon proper fastening. He opined that the Nylock nut was not installed properly at the heim joint of the accident gyrocopter. The Air Command International, Inc. Commander Elite Single-Place Assembly Manual (provided with the gyrocopter kit purchase) contains a section regarding the installation of hardware. It states that that the Nylock nuts comprise a nylon insert that locks the nut onto the threads of the bolt, preventing the nut from loosening. It adds that the Nylock nuts can be used more than once and still ensure a proper lock. The manual specifies that during a preflight inspection, the pilot should verify the integrity of the nut by twisting it in a counterclockwise direction. If the nut moves during this check, it should be replaced before the gyrocopter is flown. The manual additionally gives the bolt torque specification of 30 to 50 inch-pounds.