CEN13LA325

The pilot reported that, after completing a low pass and while in a climbing right turn, he heard the engine "sputter" and then noted that both the engine and main rotor speeds had dropped. The pilot stated that he entered an autorotation to a field because there was not enough altitude to fully recover from the partial loss of engine power. The helicopter bounced during the initial collision with terrain. A postaccident examination of the helicopter and an operational test run of the engine did not reveal any preaccident mechanical malfunctions or failures that would have prevented normal operation.

On June 6, 2013, at 1730 central daylight time, a Robinson Helicopter Company model R22 Beta helicopter, N137DF, was substantially damaged during a collision with terrain near New Braunfels, Texas. The commercial pilot was not injured, but his passenger sustained minor injuries. The airplane was registered to Davis Pharmaceutical Consulting and operated by Bratcher Aviation, under the provisions of 14 Code of Federal Regulations Part 91, without a flight plan. Day visual meteorological conditions prevailed for the local sight-seeing flight that departed a private residence near New Braunfels, Texas, about 1715.The pilot reported that the helicopter was trailered to the residence of the passenger who contracted the sight-seeing flight. After departure, the flight made several passes over the passenger's property and a nearby cornfield at an altitude of about 500 feet above the ground. The pilot reported that after completing a low pass over the cornfield he entered a climbing right turn to return to the passenger's property. Shortly after establishing the climbing turn he heard the engine "sputter" and experienced a reduction in both engine and main rotor speed. The pilot stated that he entered an autorotation because the helicopter did not have enough altitude to fully recover from the loss of both engine and rotor speed. The helicopter bounced during the initial collision with terrain before tumbling through the cornfield. The pilot stated that about 100 feet of corn was damaged during the accident sequence. Following the accident, the pilot and passenger were able to release their restraints and exit the wreckage. An on-scene investigation was completed by inspectors with the Federal Aviation Administration (FAA). Their examination revealed that the helicopter had entered cornfield in a level attitude, bounced, and then went over onto its side. The FAA examination confirmed flight control continuity for the collective and cyclic systems from the cockpit controls to the main rotor swashplate assembly. The tail rotor control tubes were fractured where the tailboom had separated from the fuselage. Engine throttle control was confirmed from the cockpit to the engine. The main and auxiliary fuel tanks contained about 10 gallons and 2.5 gallons of aviation fuel, respectively. There was no evidence of a fuel leak at the accident site. The wreckage was recovered to a storage facility where an operational engine test run could be performed. On August 16, 2013, the engine was test run under the supervision of a National Transportation Safety Board investigator. The investigator reported that the damaged main transmission drive belts had to be removed to facilitate the test run. The observed belt damage was consistent with impact damage. The engine started without hesitation and responded to throttle movements throughout the test run. The lack of main transmission belts prevented operating the engine at a full power setting; however, no anomalies werenoted while operating at various engine speeds during the test run. A magneto check confirmed that both magnetos were operational. Following the engine test run, a differential pressure test indicated that all six cylinders had compression values at or above 76 pounds per square inch (psi) with a reference pressure of 80 psi. The test run and examination did not reveal any anomalies that would have prevented normal engine operation. The nearest aviation weather reporting station was located at New Braunfels Regional Airport (KBAZ), New Braunfels, Texas, about 5 miles north of the accident site. At 1751, the KBAZ automated surface observing system reported: variable wind direction at 4 knots, visibility 10 miles, sky clear, temperature 33 degrees Celsius, dew point 19 degrees Celsius, and an altimeter setting 29.77 inches of mercury. The airport elevation was 651 feet mean sea level. The calculated density altitude was 3,302 feet.