ERA23LA307

The pilot’s inability to maneuver the helicopter for recovery after experiencing a strong, unanticipated tailwind in a confined operating area, which resulted in a descent and subsequent impact with terrain.

The pilot was operating the helicopter near maximum gross weight about 400 ft above ground level, following the terrain for an aerial observation flight. About 10 seconds into a descent, over a hilltop toward the next power transmission line, the helicopter encountered a strong tailwind. Noting a loss of airspeed, the pilot lowered the collective to gain airspeed; however, the helicopter continued to slow and descend. The pilot further lowered the collective and pushed the cyclic forward, but this was ineffective in increasing the helicopter’s airspeed. Given the low operating profile in the confined surveying location between power transmission lines and trees, the pilot did not have adequate space to compensate for the tailwind condition or turn the helicopter into the wind. Consequently, the helicopter continued to descend until it impacted the ground. The pilot reported that there were no preimpact mechanical malfunctions or failures of the helicopter that would have precluded normal operation and stated (and a review of meteorological data confirmed) that the stronger than anticipated tailwinds arrived before the forecasted time.

On July 21, 2023, about 1105 eastern daylight time, a Bell 206B, N9913K, was substantially damaged when it was involved in an accident near Terra Alta, West Virginia. The pilot and a crewmember sustained serious injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight. The pilot and equipment operator departed Morgantown Municipal Airport/Walter L Bill Hart Field (MGW), Morgantown, West Virginia, about 1039 to survey power transmission lines in the local area. The pilot was operating the helicopter near its maximum gross weight, at an altitude of 400 to 450 ft above ground level, and an airspeed of 45 knots. After completing one survey line, they topped a hill and were about 10 seconds into their descent, following the terrain toward the next power transmission line, when the pilot felt a "push." According to the pilot, the helicopter’s airspeed started to drop due to a tailwind, so he gently lowered the collective. The helicopter continued to descend and he noted that the airspeed had bled off to a value below effective translational lift. He pushed the cyclic forward for airspeed and further lowered the collective, with about 85% power applied; however, the helicopter continued to lose altitude and the helicopter's proximity to the power transmission lines and trees prevented him from being able to turn the helicopter into the wind to recover. Realizing that he could not recover, he hugged the tree line to avoid hitting the power lines. When the helicopter dropped below the trees, he pulled up on the collective to cushion the landing. The helicopter impacted the ground skids first and swung to the right. The pilot reported that he did not experience any mechanical malfunctions or failures with the helicopter during the accident flight. Examination of the accident site by a Federal Aviation Administration inspector revealed that the helicopter came to rest on its right side between the trees and the power transmission lines. Examination of the wreckage revealed that the cockpit was crushed, the skids had separated, and the main rotor had sheared off at the shaft. When asked about the weather that day, the pilot responded that they were not expecting that weather at that hour, and that the high wind had not been forecast to begin until 2 1/2 hours later. He added that they never flew if the gusts were greater than 15 knots. He was later informed that at the time of the accident the wind was gusting between 15 and 20 knots. The 1105 automated weather report from Garrett County Airport (2G4), Oakland, Maryland, located about 16 miles northeast of the accident site, included variable wind of 6 knots gusting to 13 knots. The Terminal Aerodrome Forecast (TAF) issued for MGW included westerly wind at 6 knots, increasing to 8 knots gusting to 16 knots at 1300. A High-Resolution Rapid Refresh (HRRR) model obtained from the NOAA Air Resource laboratory for the accident site area at 1100 indicated a surface wind from 290° at 9 knots with potential gusts to 15 knots.