Alpine, TX, USA
N4073S
ROBINSON R22
While on a cross-country flight over mountainous terrain, the helicopter impacted the side of a mountain at 6,800 feet, about 90 feet below the crest. The investigation revealed that the tail rotor hit the side of the mountain first. Wreckage was distributed down the side of the mountain to about the 6,500-foot level. Density altitude, calculated using a pressure altitude of 6,800 feet and an estimated temperature of 85 degrees, was 9,900 feet. The helicopter's gross weight was calculated to be 1,229 pounds. Maximum gross weight for out-of-ground effect hover performance at 9,900 density altitude was 1,210 pounds. Examination of the wreckage revealed no evidence of pre-impact flight control malfunction or airframe or system failure. The engine performed within manufacturer specifications and certification standards during a postaccident test run. The pilot had no memory of the accident, there were no witnesses, and the phase of operation was unknown.
HISTORY OF FLIGHTOn September 5, 1992, at approximately 1630 central daylight time, a Robinson R22 Beta helicopter, N4073S, was destroyed when it collided with mountainous terrain near Alpine, Texas. The helicopter departed David Wayne Hooks Airport, Houston, Texas, at approximately 1009 with a final destination of Marfa, Texas. A company flight plan had been filed. The pilot sustained serious injuries and the rated passenger received fatal injuries. Visual meteorological conditions prevailed for the personal flight. Interviews with the pilot and followup investigations conducted by the investigator in charge (IIC) and a Federal Aviation Administration (FAA)inspector revealed the facts in this paragraph. The pilot weighed about 160 pounds, and the passenger weighed about 190 pounds. Usable fuel was 29.7 gallons with a basic empty weight of 856.2 pounds. About 5 pounds of baggage were on board. One enroute fuel stop was made at Sonora, Texas, at approximately 1315 and 28.9 gallons of fuel was purchased. The helicopter departed Sonora, Texas, at approximately 1345 with a computed takeoff weight of approximately 1,409 pounds. Interviews conducted by the FAA inspector and the IIC with the company and the pilot revealed the facts in this paragraph. The pilot remembered the original departure clearance and the takeoff. He recalled awakening on the mountain during the night time and setting several "fires to attract attention and the fires getting out of control." Upon seeing the lights of a city, he traveled on foot in that direction and remembered two sunrises and locating a pool of water from which he drank and then bathed. Eventually, he heard a car and upon "shouting" for help was rescued and taken to the hospital. During an interview conducted by the FAA inspector with the Sheriff Departments in the area, the facts in this paragraph were reported. The pilot had been located in an apple orchard near the sunny Glen Subdivision of Alpine, Texas, at approximately 1900 on September 7, 1992. The pilot was disoriented; however, the pilot mentioned the helicopter and starting the fires on the mountain. At approximately 2345, the CAP and DPS found the accident site at 30 degrees 23 minutes North and 103 degrees 47 minutes West. Fire departments in the site area who were interviewed by the FAA inspector, stated that they had received reports of fires in the mountains at approximately 0100 during the morning of September 6, 1992. However, the fires had been reported on a different mountain. PERSONNEL INFORMATIONThe pilot held a French medical certificate which had been issued on October 4, 1992. On August 3, 1992, the pilot had been issued a United States Department of Transportation (USDOT) commercial pilot certificate with the helicopter rating on the basis of French pilot license #13667. The pilot rated passenger had been issued a USDOT commercial pilot certificate with the helicopter rating on the basis of his Canadian pilot license #171939 on June 12, 1992. According to relatives in the enclosed statement, the pilot and passenger had flown together more than one hundred hours and both were accustomed to mountainous conditions in several foreign countries. AIRCRAFT INFORMATIONA review of the maintenance records, manufacturer data, and interviews with the operator by the IIC, revealed the facts in this paragraph. The helicopter date of manufacture was May 7, 1991. The 160 horsepower engine was derated to 131 horsepower for the helicopter. The basic empty weight had been established on July 17, 1991, and the certificate of airworthiness issued. The helicopter had been maintained under a one hundred hour inspection program. A registration certification was issued to the company on September 16, 1991. The altimeter and encoder had been certified to 16,000 feet on July 2, 1991. The helicopter had been flown 5.5 hours on the date of the accident. Maximum gross weight for the helicopter was 1,370 pounds. Calculations indicate that the center of gravity at the time of the accident was 96.7 inches, which was within the maximum allowable range of 95.9 to 100.00 inches. Calculations also indicate that the helicopter's gross weight was about 1,229 pounds at the time of the accident. Maximum gross weight for out-of-ground effect hover performance at a density altitude of 9,900 feet (6,800 feet pressure altitude at a temperature of 85 degrees) was 1,210 pounds, according to the Robinson R22 Pilot's Operating Handbook. METEOROLOGICAL INFORMATIONThe closest weather observation to the accident site was the AWOS reporting equipment at Marfa, Texas. The 1635 observation reported a temperature of 90 degrees Fahrenheit. The accident site was approximate 11 miles east of the reporting airport, and the temperature was estimated as 85 degrees Fahrenheit. The initial impact point was at an elevation of 6,800 feet. Density altitude at the site was calculated at 9,900 feet. The density altitude chart is included as a part of this report. AIRPORT INFORMATIONA review of the maintenance records, manufacturer data, and interviews with the operator by the IIC, revealed the facts in this paragraph. The helicopter date of manufacture was May 7, 1991. The 160 horsepower engine was derated to 131 horsepower for the helicopter. The basic empty weight had been established on July 17, 1991, and the certificate of airworthiness issued. The helicopter had been maintained under a one hundred hour inspection program. A registration certification was issued to the company on September 16, 1991. The altimeter and encoder had been certified to 16,000 feet on July 2, 1991. The helicopter had been flown 5.5 hours on the date of the accident. Maximum gross weight for the helicopter was 1,370 pounds. Calculations indicate that the center of gravity at the time of the accident was 96.7 inches, which was within the maximum allowable range of 95.9 to 100.00 inches. Calculations also indicate that the helicopter's gross weight was about 1,229 pounds at the time of the accident. Maximum gross weight for out-of-ground effect hover performance at a density altitude of 9,900 feet (6,800 feet pressure altitude at a temperature of 85 degrees) was 1,210 pounds, according to the Robinson R22 Pilot's Operating Handbook. WRECKAGE AND IMPACT INFORMATIONThe top of the mountain was 6,895 feet. There was no physical evidence that the helicopter had landed on the mountain top. A portion of a tail rotor blade tip, which was painted white, was located on the downslope at approximately 6,800 feet on the south side of the mountain. The slope to the first impact point was approximately 28 degrees. The wreckage distribution magnetic heading was measured as 180 degrees. White paint transfer was found on a rock approximately 48 feet from the tail rotor tip. The remainder of the wreckage distribution was on a downslope of approximately 35 degrees. Numerous pieces of the tailboom were found and exhibited striations. The tailrotor push pull tubes and the tailrotor driveshaft were not located. Skids, doors, and the instrument panel were found as the distribution path continued to the south. The closing bolt was secure on the doors. The tailrotor gearbox was located at approximately 6,675 feet. The gear box rotated and the push pull parts were present and the push pull tube fractured. One main rotor blade was located at approximately 6,552 feet. The blade exhibited striations near the tip. The main wreckage came to rest at an elevation of approximately 6,515 feet. The total distance from the initial impact point to the final resting place was approximately 285 feet. The mast, transmission, and engine remained attached. One main rotor blade was attached to the mast. Flight control continuity was established. Approximately three gallons of fuel was siphoned from the fuel tanks. The engine representative examined the engine and reported impact damage of various components. The powerplant report is included as a part of this report. ADDITIONAL INFORMATIONThe helicopter was released to the owner's representative following the investigation. MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy and toxicological testing were not ordered by the IIC for the rated passenger. The pilot suffers amnesia and to date has not remembered the flight. TESTS AND RESEARCHAn engine ground test run was conducted by the Lycoming factory on December 3, 1992. Engine operation was conducted on the factory test cell and operation was normal through full power range. The engine representative report and the engine test log are included as a part of this report.
Failure by the pilot-in-command, for unknown reasons, to maintain sufficient altitude to clear surrounding terrain. Factors were mountainous terrain and high density altitude.
Source: NTSB Aviation Accident Database
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