NTSB Factual Report

On August 5, 2004, at 1545 central daylight time, a Bell 47G-3B-1 single-engine helicopter, N47713, was substantially damaged during a simulated autorotation landing near Troy, Texas. The helicopter was registered to Tumbleweed Aviation LLC, of Jackson, Louisiana, and operated by Brazos Helicopter LLC, of Bruceville, Texas. The flight instructor (CFI) and commercial pilot receiving instruction were not injured. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 instructional flight. The cross-country flight originated from a private heliport near McClennan County, Texas, at 1445, destined for Temple, Texas.

The 10,120-hour CFI reported in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that after performing a series of practice autorotations and stuck pedal recoveries, the flight continued en route to Temple, Texas. The flight instructor and pilot receiving instruction decided to execute one last precision touchdown practice autorotation to a field.

At an altitude of 1,200 feet above ground level (agl), the CFI initiated the autorotation at an airspeed of 60 miles per hour (mph). At an altitude approximately 75 feet agl, the pilot "raised the nose" of the helicopter "to begin the termination of the auto[rotation]." At an altitude approximately 20 feet agl, "initial collective pitch was applied to cushion the sink rate and slow the remainder of the groundspeed." After the pilot increased the throttle, he applied "all remaining collective pitch" and noticed the sink rate was not decreasing. Subsequently, the helicopter impacted the ground and then bounced back into the air.

The CFI stated that the main rotor blades severed the tail boom as the helicopter became airborne. As the helicopter started to rotate, throttle was reduced and the helicopter landed upright in the field. The CFI further stated the wind after the accident was from 350 degrees, approximately 10 knots.

Examination of the helicopter by an Federal Aviation Administration (FAA) inspector, who responded to the site of the accident, revealed the tail boom was separated from the fuselage, both main rotor blades damaged, and the landing skids were spread apart.

The CFI reported in the NTSB Form 6120.1/2 section, Recommendation (How could this accident have been prevented?) that one should "perform autorotation practice only when wind direction indicators are easily visible." Also, one should "pay more attention to aircraft performance degradation due to high density altitude."

At 1655, the automated weather observing system at Draughon-Miller Central Texas Regional Airport (TPL), near Temple, Texas, located 8 miles southwest of the accident site, reported wind from 040 degrees at 6 knots, visibility 10 statue miles, sky condition clear, temperature 84 degrees Fahrenheit, dew point 70 degrees Fahrenheit, and an altimeter setting of 29.94 inches of Mercury.

The density altitude was calculated by the NTSB investigator-in-charge to be 2,485 feet mean sea level.

NTSB Probable Cause

The flight instructor's improper flare, resulting in a hard landing. A contributing factor was the high density altitude.