NTSB Identification: ERA12MA005
14 CFR Part 91: General Aviation
Accident occurred Tuesday, October 04, 2011 in New York, NY
Probable Cause Approval Date: 02/28/2013
Aircraft: BELL 206B, registration: N63Q
Injuries: 2 Fatal,1 Serious,2 Uninjured.
NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft accident report.
The purpose of the flight was for the pilot to take friends on a sightseeing flight around New York City. After the helicopter landed at the East 34th Street Heliport (6N5), the pilot did not shut down the engine while the passengers boarded. The pilot had initially anticipated taking two passengers on the flight, but the two passengers brought two additional adults with them who also boarded the helicopter. The pilot did not conduct a safety briefing or mention life vests available on board the helicopter, complete performance planning, or perform weight-and-balance calculations before takeoff. (The heliport personnel did not conduct a safety briefing and were not required to do so.)
The helicopter departed 6N5 in a rearward hover and transitioned over the shoreline from an in-ground-effect condition to an out-of-ground-effect (OGE) condition while climbing to about 60 feet above the water. As the pilot completed a pedal turn into the wind, the helicopter yawed, and what was likely the low rotor rpm audio warning sounded. The pilot believed that he heard an engine-out warning and responded by turning back toward 6N5, which oriented the tail into an adverse (tail) wind condition. He then confirmed normal engine operation by the N1 gas tachometer and concluded that the initial yaw was “weathervaning” as opposed to an engine malfunction. After the pilot increased collective pitch, the helicopter entered an uncommanded right yaw that accelerated into a spin around the main rotor mast that could not be corrected by application of full left pedal. At this point, the pilot believed that the helicopter had tail rotor drive failure or encountered a loss of tail rotor effectiveness (LTE). Witnesses described the helicopter as descending in an uncontrolled spin before it contacted the water, where it then rolled inverted and sank.
The pilot and front-seat passenger, who were not injured, attempted to help the aft-seat passengers evacuate as the helicopter filled with water and sank. One passenger drowned at the scene, and two passengers later died in a hospital from complications of near drowning. (Title 14 Code of Federal Regulations 830.2 defines fatal injury as “any injury which results in death within 30 days of the accident.” Because one passenger’s death occurred 33 days after the accident, she is listed as a “serious injury” in this report.) The helicopter was difficult to exit because it was inverted in the water.
Examination of the wreckage revealed no evidence of any preimpact failures or malfunctions of the engine, drive train, main rotor, tail rotor, or structure of the helicopter. Additionally, the main and tail rotors showed indications of rotation at the time of water impact.
The investigation determined that the helicopter was loaded to an overweight condition, likely because the pilot did not anticipate having two additional passengers onboard the helicopter and because he did not perform weight-and-balance calculations. The front-seat passenger stated in a postaccident interview that the pilot did not ask for anyone’s weight or perform any calculations before takeoff. The passenger weights that the pilot provided investigators following the accident were significantly less than the weights provided by medical personnel and the surviving passenger. The calculated empty weight of the helicopter at its most recent weight-and-balance check on October 21, 2008, was 1,914.52 pounds, and the estimated empty weight postaccident, including residual water, was estimated to be 2,146.8 pounds. Therefore, investigators determined that the estimated gross weight of the helicopter at takeoff was likely between 3,228 pounds and 3,461.2 pounds. The manufacturer’s maximum allowable gross weight at takeoff was 3,200 pounds.
Federal Aviation Administration Advisory Circular (AC) 90-95, “Unanticipated Right Yaw in Helicopters,” issued in February 1995, described LTE as a critical, low speed aerodynamic flight characteristic that could result in an uncommanded rapid yaw rate that does not subside of its own accord and, if not corrected, could result in the loss of aircraft control. The AC also stated, “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.” When operating at airspeeds below effective translational lift, pilots should avoid OGE hover and high power demand situations, such as low-speed downwind turns. Contributing factors for LTE included high gross weight, low indicated airspeed, and right downwind turns. Thus, it is likely that the helicopter experienced LTE shortly after takeoff because all of these factors were present at the time of the accident. Due to the pilot’s ineffective actions and his failure to anticipate and correct for these conditions, he was unable to recover.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to anticipate and correct for conditions (high gross weight, low indicated airspeed, and a right downwind turn) conducive to loss of tail rotor effectiveness (LTE), which resulted in LTE and an uncontrolled spin. Contributing to the accident was the pilot’s inadequate preflight planning, which resulted in the helicopter being in excess of its maximum allowable gross weight at takeoff. Full narrative available
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