ERA19LA171

The pilot was attempting to reposition the helicopter to a helipad after refueling at a riverfront heliport. On his first approach to the helipad in a gusting, quartering tailwind, the pilot felt the onset of a loss of tail rotor effectiveness (LTE) and aborted the approach and went around. He climbed the helicopter over the water, turned back toward the helipad, and again felt the onset of LTE. The nose of the helicopter began a yaw to the right, and application of full left pedal failed to arrest the yaw. The helicopter then entered an uncontrolled right spin around its mast and descended to water contact, resulting in substantial damage to the airframe. The pilot reported that there were no preimpact mechanical malfunctions of failures with the helicopter that would have precluded normal operation.

On May 15, 2019, at 1426 eastern daylight time, a Bell 206 L4 helicopter, N26BB, operated by Zip Aviation, was substantially damaged during a forced landing to the Hudson River while maneuvering for landing at the West 30th Street Heliport (JRA), New York, New York. The commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the repositioning flight conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot stated that he had just refueled on the fuel deck on the south side of JRA and was told to reposition the helicopter to pad No. 4 on the northern side of the trailer that served as the office and passenger terminal for the heliport. He attempted one approach to pad No. 4 but felt the onset of LTE (loss of tail rotor effectiveness) and aborted the approach and went around. He climbed the helicopter over the water, turned back toward an easterly heading to the helipad and again felt the onset of LTE. The nose of the helicopter began a yaw to the right, and application of full left pedal failed to arrest the yaw. The helicopter then entered an uncontrolled spin around its mast to the right. The pilot further stated, "I continued to attempt to maneuver the helicopter into the wind and gain some forward airspeed. This attempt did not effectively restore the tail rotor authority." According to the pilot, the loss of altitude and the helicopter's proximity to the water made a successful recovery of the spin unlikely, and he elected to deploy the floats and perform a controlled landing to the water to avoid any conflict with people or property on the shore. The pilot reported that he did not experience any mechanical malfunctions or failures with the helicopter during the accident flight; nor during any previous flights that day, which included two earlier landings at JRA. He further added that once he decided to perform a water landing, all systems, including the floats and vest worked as designed. When asked about the winds that day, the pilot said they were "pretty consistent" all day. There was no automated weather at JRA, but the person manning the radio in the trailer provided a wind advisory when landing instructions were given. When listening to automated weather reports from Newark (EWR) and Teterboro (TEB) airports, the pilot recalled hearing winds from the west, and later recalled observations reporting wind at 11 knots gusting to 22 knots, and 10 knots gusting to 18 knots. He added that traffic at Newark was landing on Runway 29, and that when traffic landed on Runway 29 "the winds had to be pretty significant." Video recordings of the accident flight displayed a sequence consistent with the pilot's account. The helicopter climbed to about 100-150 ft in a continuous right turn before the nose pitched up, and forward flight ceased as the helicopter aligned approximately with the landing spot. The nose of the helicopter yawed slowly and continuously to theright, until the helicopter entered a descent as it rotated around the main rotor mast. Just prior to descending from view and water contact, the floats deployed. The pilot held a commercial pilot certificate with ratings for rotorcraft helicopter and instrument helicopter. His most recent Federal Aviation Administration (FAA) first class medical certificate was issued on February 21, 2019. He estimated that he had 900 total hours of flight experience, 42 hours of which was in single-engine airplanes. The pilot stated that he had accrued about 100 hours in the accident helicopter make and model. According to FAA airworthiness and maintenance records, the helicopter was manufactured in 2017 and was maintained utilizing a manufacturer's continuous airworthiness program. Its most recent inspection was completed May 8, 2019 at 557 total aircraft hours. Photographs and video of the wreckage revealed the fuselage was largely intact. The helicopter came to rest upright on its flotation pontoons. The transmission, main rotor mast, and main rotor system all remained attached as a single unit but was separated from the transmission mounts and rested against the left side of the fuselage. The engine also appeared dislodged from its mounts. The FAA issued Advisory Circular (AC) 90-95, Unanticipated Right Yaw in Helicopters, in February 1995. The AC stated that LTE was a critical, low-speed aerodynamic flight characteristic which could result in an uncommanded rapid yaw rate which does not subside of its own accord and, if not corrected, could result in the loss of aircraft control. Excerpts from the AC included: LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots. Any maneuver which requires the pilot to operate in a high-power, low-airspeed environment with a left crosswind or tailwind creates an environment where unanticipated right yaw may occur. OTHER FACTORS...Low Indicated Airspeed. At airspeeds below translational lift, the tail rotor is required to produce nearly 100 percent of the directional control. If the required amount of tail rotor thrust is not available for any reason, the aircraft will yaw to the right. When maneuvering between hover and 30 knots: (1) Avoid tailwinds. If loss of translational lift occurs, it will result in an increased high power demand and an additional anti-torque requirement. (2) Avoid out of ground effect (OGE) hover and high power demand situations, such as low-speed downwind turns. (3) Be especially aware of wind direction and velocity when hovering in winds of about 8-12 knots (especially OGE). There are no strong indicators to the pilot of a reduction of translation lift... (6) Stay vigilant to power and wind conditions.