Accident Sequence
On May 15, 2019, at 1426 eastern daylight time, a Bell 206 L4 helicopter, registration N26BB, operated by Zip Aviation, was substantially damaged during a forced landing to the Hudson River. The aircraft was maneuvering for landing at the West 30th Street Heliport (JRA), New York, New York, when the incident occurred. The commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the repositioning flight conducted under 14 CFR Part 91.
According to the pilot, he had just refueled on the fuel deck on the south side of JRA and was instructed to reposition the helicopter to pad No. 4 on the northern side of the trailer serving as the heliport's office and passenger terminal. He attempted an approach to pad No. 4 but felt the onset of loss of tail rotor effectiveness (LTE) and aborted the approach, going around. He climbed 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 full left pedal application failed to arrest the yaw. The helicopter then entered an uncontrolled spin around its mast to the right. The pilot 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."
Given the loss of altitude and proximity to the water, the pilot determined that a successful recovery from the spin was unlikely and elected to deploy the floats and perform a controlled landing to the water to avoid conflict with people or property on shore. The pilot reported no mechanical malfunctions or failures during the accident flight or previous flights that day, which included two earlier landings at JRA. He added that once he decided to perform a water landing, all systems, including the floats and vest, worked as designed.
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, forward flight ceased as the helicopter aligned approximately with the landing spot, and the nose yawed slowly and continuously to the right until the helicopter entered a descent while rotating around the main rotor mast. Just prior to descending from view and water contact, the floats deployed.
Pilot Information
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 900 total hours of flight experience, with 42 hours in single-engine airplanes. He had accrued about 100 hours in the accident helicopter make and model.
Aircraft Information
According to FAA airworthiness and maintenance records, the helicopter was manufactured in 2017 and maintained using a manufacturer's continuous airworthiness program. Its most recent inspection was completed on 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 remained attached as a single unit but separated from the transmission mounts and rested against the left side of the fuselage. The engine also appeared dislodged from its mounts.
Meteorological Information
The pilot reported that winds 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. The pilot recalled hearing automated weather reports from Newark (EWR) and Teterboro (TEB) airports, with winds from the west, and later 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, which indicated "the winds had to be pretty significant."
Advisory Circular
The FAA issued Advisory Circular (AC) 90-95, "Unanticipated Right Yaw in Helicopters," in February 1995. The AC stated that LTE is a critical, low-speed aerodynamic flight characteristic that can result in an uncommanded rapid yaw rate which does not subside on its own and, if not corrected, could result in loss of aircraft control. Excerpts from the AC noted that LTE is not related to a maintenance malfunction and may occur in all single main rotor helicopters at airspeeds less than 30 knots. Maneuvers requiring high power and low airspeed with a left crosswind or tailwind create an environment where unanticipated right yaw may occur. At airspeeds below translational lift, the tail rotor must produce nearly 100 percent of directional control; if required thrust is unavailable, the aircraft will yaw right. The AC advises avoiding tailwinds, out of ground effect hover, and high-power demand situations when maneuvering between hover and 30 knots, and staying vigilant to power and wind conditions.