NYC04FA117

The helicopter was hovering at 1,000 to 1,200 feet, during an electronic news gathering flight, when it experienced a loss of hydraulic system power. The pilot stated he did not have any specific recollection regarding the beginning of the accident sequence. He said that he felt the helicopter was not responding to his control inputs, "the way it should be." He also did not recall reporting any specific problems over the radio; however, review of communication recordings revealed that the pilot stated he experienced a "tail rotor failure." Another helicopter captured the accident sequence from its onboard video camera. The accident helicopter was observed entering a steep descent and quickly leveling off. A fairly constant, level attitude and heading were briefly maintained before the helicopter came to an unstable hover and began an approximate two revolution left rotation about its vertical axis. During the rotation, the helicopter descended and struck the roof parapet of a 4-story building, before it impacted and came to rest on the roof of an adjacent 2-story building. Examination of the helicopter's hydraulic system revealed that the hydraulic pump drive belt had been installed inside-out and failed due to an overload, leading to a full hydraulic system failure. According to Eurocopter's emergency procedures for the helicopter, the pilot action following a hydraulic system failure would be to "calmly reduce collective pitch and adjust the airspeed to between 40 and 60 knots in level flight" and then cut off the hydraulic pressure, by moving the toggle switch located on the collective pitch lever to off. The procedures further state that when the accumulators are exhausted, the control forces become significantly higher, but "not unmanageable." The helicopter could be controlled without the main and tail rotor servo actuators being hydraulically powered, but this would require the pilot to apply "non-negligible" forces that are substantially different than the forces required with the hydraulic system operating properly. The hydraulic system toggle switch was found in the "on" position. The "flat" hydraulic pump drive belt had accumulated about 440 hours, and had a service life limit of 600 hours. On May 11, 2004, Eurocopter issued a service bulletin which recommended the installation of a"Poly-V" hydraulic pump belt. The improved belt comprised multiple longitudinal "V" shapes on its inner surface that mated with similar surfaces on the hydraulic pump pulley and had a service life limit of 1,500 hours. Eurocopter recommended that all "flat" drive belts be replaced with the "Poly-V" belts.

History of flight

On May 4, 2004, about 1820 eastern daylight time, a Eurocopter AS-350BA, N4NY, operated by Helinet Aviation Services as WNBC News Chopper 4, was destroyed after it experienced a loss of control while hovering, and impacted residences in Brooklyn, New York. The certificated commercial pilot and a passenger sustained serious injuries, while one passenger sustained minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed for the local flight that departed the Teterboro Airport (TEB), Teterboro, New Jersey. The electronic news gathering (ENG) flight was conducted under 14 CFR Part 91.

The accident flight was the helicopter's second flight of the day. The pilot was seated in the front right seat, a reporter was seated in the front left seat, and a recently hired pilot was seated in the rear middle seat, for both flights.

The first flight departed Teterboro Airport about 1400 and returned about 1600, without incident. The helicopter was then refueled, preflight inspected, and departed about 1630 for a regularly scheduled ENG flight.

During an interview, the pilot stated he recalled hovering at 1,000 to 1,200 feet; however, he did not have any specific recollection regarding the beginning of the accident sequence. His first memory was of the helicopter in an extreme nose down position. He pulled aft on the cyclic and the helicopter began to pitch up; however, he felt that the helicopter was not responding to his control inputs, "the way it should be," and he attempted to land on a rooftop. The pilot could not provide any specific details regarding the control forces he experienced; except that he "made full inputs", and was "working the pedals back and forth, but nothing seemed to happen." He did not recall observing any warning lights, or hearing any audible warnings.

The pilot was communicating with the John F. Kennedy International Airport (JFK) air traffic control tower at the time of the accident. The pilot did not recall reporting any specific problems over the radio; however, review of communication recordings revealed that the pilot stated he experienced a "tail rotor failure."

The reporter stated that the helicopter was hovering over Flatbush Avenue, and East 29th street. He was preparing to file a report, when the helicopter "veered violently to the left." He also heard a warning horn and observed a red or green warning light illuminate. He recalled the helicopter being "out of control and going into a nose dive," before he blacked out. He had no further memory of the accident.

The pilot seated in the rear seat stated that the helicopter was hovering at an altitude of about 1,300 feet, and facing between 270 and 290 degrees, when it pitched down and yawed to the left. He was not able to look at the instrument panel and was not aware if any warning lights illuminated; however, he did hear an intermittent horn. The helicopter was unstable as it pitched up, down and entered a dive.

The helicopter descended and struck the roof parapet of a 4-story building, before it impacted and came to rest on the roof of an adjacent 2-story building, on Cortelyou Road, between East 25th and 26th streets.

A portion of the accident flight, including the impact, was recorded by a WABC News Channel 7 helicopter. In addition, a portion of the accident flight preceding the impact was recorded from the accident helicopter. All images of the accident were forwarded to the Safety Board's Vehicle Recorder Division for further review.

The accident occurred during the hours of daylight, and was located approximately 40 degrees, 38.643 minutes north latitude, and 73 degrees, 57.187 minutes west longitude.

Personnel information

The pilot held a commercial pilot certificate for rotorcraft, with an instrument rating. He attended a Eurocopter factory training course for the AS-355, which utilized a dual hydraulic pump system, on June 25, 1982. He had not attended a factory training course for the AS-350. He was hired by Helinet Aviation Services during December 1996. He had not flown at all during April through September 2003. He began flying part-time in October, and had been flying about 5 days a week since January 2004. The pilot's most recent flight review was conducted on January 13, 2004. The pilot stated that his logbook was not current. He estimated that he had accumulated about 6,500 hours of total flight experience, which included about 350 hours in the same make and model as the accident helicopter. Helinet reported that the pilot had flown about 20 hours during the 30 days that preceded the accident.

The pilot's most recent Federal Aviation Administration (FAA) second class medical certificate was issued on May 16, 2003.

The pilot seated in the rear seat held a commercial pilot certificate for rotorcraft, with an instrument rating and a certified flight instructor certificate. He was hired by Helinet Aviation Services on April 19, 2004, and completed a Eurocopter factory AS-350 training course on April 30, 2004.

He reported 3,000 hours of total flight experience on his most recent application for an FAA second class medical certificate, which was issued on April 8, 2004.

Aircraft information

The helicopter was manufactured in 1988 and purchased by the owner, Horsham Valley Airways, Inc., on July 3, 2002. The helicopter was leased to Helinet Aviation Services beginning on March 8, 2004. At the time of the accident, the helicopter had been operated for about 8,426 total hours. The helicopter had been operated for about 48 hours since it's most recent 100 hour inspection, which was performed on April 19, 2004.

The helicopter was equipped with a Turbomeca Arriel 1 engine, which was overhauled on October 23, 2003. At the time of the accident, the engine had accumulated about 6,740 total hours since new, and 441 hours since the overhaul.

Hydraulic System description

According to the AS-350BA flight manual, to reduce pilot workload, the flight controls were hydraulically boosted in order to give very light control load on the cyclic stick, collective lever, and tail rotor pedals. There were three main rotor servos, one longitudinal and two lateral; and also a tail rotor servo for yaw control. A single gear-type hydraulic pump generated hydraulic power. The hydraulic pump was mounted on the rear of the transmission housing, and was driven at a constant speed, with a constant discharge flow of 6 liters per minute, by a flat synthetic drive belt. The belt was driven by a pulley located immediately forward of the main drive shaft. The three main rotor servos each contained a nitrogen pre-charged accumulator that was designed to provide the pilot with continued hydraulic assistance for a limited time in the event of a hydraulic pressure loss. The tail rotor servo was not equipped with an accumulator.

A toggle switch located on the collective pitch lever allowed the hydraulic system to be selected on and off. Selecting the switch to "off" position opened three-solenoid valves, one on each of the main servo actuators, and caused any residual or hydraulic backpressure at the actuator to be dissipated. This would reduce the forces required to move the servo actuators providing a manual reversion capability to allow the pilot to retain control of the helicopter in the event of a servo jam or a loss of hydraulic system pressure. The hydraulic system low-pressure switch would activate when the hydraulic system pressure dropped below approximately 35 bars, or 515 PSI. This would then illuminate a red "HYD" warning light on the Warning Caution Advisory Panel (WCAP) and produce a continuous tone from a warning horn. The same horn provided warning of low main rotor RPM. The horn would remain on until the failure condition was removed or the pilot canceled the horn. The horn may be cancelled by pressing the horn cancel button on