HISTORY OF FLIGHT On May 12, 2003, about 1200 mountain standard time (MST), a MDHI OH 6A, N6636H, collided with terrain near Pan Tak, Arizona. The helicopter was owned and operated by U.S. Border Patrol as a public use aircraft under the provisions of 14 CFR Part 91. The commercial pilot in command (PIC) sustained minor injuries. The second commercial rated pilot/observer sustained serious injuries; the helicopter was destroyed. The cross-country flight departed Ajo, Arizona, about 1130 en route to Tucson, Arizona. Day visual meteorological conditions prevailed, and no flight plan had been filed. The primary wreckage was at 32 degrees 02 minutes north latitude and 111 degrees 31 minutes west longitude. The PIC and the flying pilot (FP) reported that while flying about 300-400 feet agl, and at 90 knots indicated airspeed, they heard two loud bangs followed by a brief, violent shudder in the airframe. The FP attempted to control the yaw of the helicopter by applying left pedal. The anti-torque pedals were not effective, the FP pilot told the PIC "I've got nothing." The PIC took the flight controls and attempted control the yaw with the use of the cyclic. The PIC stated that whenever he made a control input the helicopter nose would tuck. He had to hold aft and right cyclic to keep the helicopter under some control. Once the helicopter yawed close to 90-degrees the PIC closed the throttle and entered into an autorotation. The rotor rpm had bleed off the PIC told the FP "we are going to hit hard." The helicopter hit the ground and bounced back into the air and rotated longitudinally and came to rest on the left side of the helicopter. The helicopter came to rest on mostly level desert terrain. Most of the major components to the helicopter were located in the area of the main wreckage. The tail rotor gearbox and tail rotor blade assembly were missing from its attachment point of the tail boom. A search of the area for the tail rotor assembly or other related pieces of the helicopter were initially unsuccessful. During the search for the missing tail rotor components, searchers found a U.S. Border Patrol flight jacket. The jacket was located 4,329 feet West of the accident site. The flight jacket was found in multiple pieces scattered about 25 yards apart. Sleeves, the collar, a pocket and the main body of the jacket were recovered. Examination of the flight jacket had red and white colored paint transfers. The tail rotor blades on the accident helicopter were painted with red and white colored paint. The following day the tail rotor and gearbox assemblies were located 3,168 feet west of the accident site and 1,161 feet east of the jacket location. Examination of the tail rotor assembly and tail boom of the helicopter revealed scrape marks, which are similar dimensionally to the zipper on the flight jacket. The helicopter manufacturer representative computed the weight and balance for the accident helicopter, both before and after the loss of the tail rotor and gearbox assemblies. The calculations show that the helicopter was outside the forward limit of the helicopter CG range. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed the pilot held a commercial pilot certificate with a helicopter, airplane single-engine land ratings, and an instrument helicopter and airplane rating. The pilot held a second-class medical certificate that was issued on January 30, 2003. It had the limitations that the pilot must wear corrective lenses. The pilot/operator aircraft accident report (6120.1/2) indicated the PIC had a total flight time of 4,236 hours. He logged 50 hours in the last 90 days, and 30 in the last 30 days. He had an estimated 2,238 hours in this make and model. The FP had a total flight time of 2,620 hours. He had 80 hours in this make and model. AIRCRAFT INFORMATION The helicopter was a Hughes OH6-A, serial number 780594. The operator reported helicopter's total airframe time of 5,859.3 hours at the last Approved Inspection Program (AAIP) inspection. An AAIP inspection was completed on February 24, 2003. At the time of the accident the helicopter had 60 hours since the last inspection. The helicopter had an Allison/Rolls Royce 250C20B engine, serial number CAE836913, installed. Total time on the engine at the last AAIP inspection was 1,562.5 hours. METEOROLOGICAL INFORMATION The closest official weather observation station was Tucson International Airport, Tucson, Arizona (TUS), which was located 37 nautical miles (nm) northeast of the accident site. The elevation of the weather observation station was 2,403 feet msl. A routine aviation weather report (METAR) for TUS was issued at 1155 MST. It stated: skies were clear; visibility 10 miles; winds were variable at 6 knots; temperature 91 degrees Fahrenheit; dew point 32 degrees Fahrenheit; altimeter 30.01 InHg. WRECKAGE AND IMPACT INFORMATION Investigators from the FAA, and the U.S. Border Patrol examined the wreckage at the accident scene.