VAN NUYS, CA, USA
N500WC
Aerospatiale AS350B
While hovering out of ground effect, the helicopter had a hydraulic system failure. The pilot shutoff the hydraulic accumulator pressure 5 seconds after the warning horn sounded. According to the onboard cameraman the helicopter began to spin. The pilot stabilized the helicopter, and reported to other news helicopters filming the night time event, that she had lost hydraulic pressure and was experiencing control problems. Another pilot suggested that the pilot consider two airports within 5 miles. The pilot elected to return to the home base, about 15 miles away. The pilot reported en route to escorting helicopters that her right leg was 'killing her.' A hover landing was attempted, and a loss of control resulted in spinning out of control to the ground. Postaccident examination revealed a failed hydraulic pump drive pulley bearing and subsequent drive belt failure. According to the rotorcraft flight manual, 'The pressure stored in the accumulators allows sufficient time to reach the 'refuge' area with hydraulic servo-assistance.' According to manufacturer representatives, that time is between 30 and 45 seconds, depending on control inputs. The pilot action is to 'Calmly reduce collective pitch and adjust the airspeed to between 40 and 60 knots in level flight. Cut off the hydraulic pressure, using collective lever pushbutton.' According FAA medical data, the pilot's last reported weight was 108 pounds and a height of 61 inches. According to pilots who are experienced in this model, body size and strength are important issues in handling this type of emergency. The manufacturer representative stated that it is an emergency, and the pilot should land as soon as practical. It was also stated that the accident pilot had recently completed the factory-training course successfully.
HISTORY OF FLIGHT On March 26, 2000, about 2213 hours Pacific standard time, an Aerospatiale AS350B, helicopter, N500WC, operated by Helinet Corporation on lease to Fox Television Stations, Inc., was substantially damaged during landing approach at Van Nuys, California. The commercial rated pilot and news cameraman passenger were both seriously injured. Visual meteorological conditions prevailed for the flight operating under 14 CFR Part 91 and a company flight plan was filed. The flight had departed Van Nuys airport about 2100, en route to televise the Academy Awards Ceremony from the helicopter at Los Angeles, California. At 2203, while hovering out of ground effect over the event, the helicopter experienced a total loss of hydraulic pressure. According to recovered videotape, the sound of a warning horn was heard for 5 seconds then quit. According to the cameraman the helicopter began to spin. The pilot stabilized the helicopter, and reported to other news helicopters filming the event, that she had lost hydraulic pressure and was experiencing control problems. Another pilot suggested that the pilot consider going to Santa Monica Airport, as they were still open. She elected to return to Van Nuys airport, about 15 miles northwest. Santa Monica and Los Angeles airports are located about 5 miles west. The flight was escorted back to Van Nuys airport by another news helicopter, with radio calls being made by the escorting pilot to relieve the workload of the pilot. The accident pilot did not declare an emergency. The escorting pilot requested priority handling from the Van Nuys control tower. The pilot requested the "Basin Arrival," landing at Helinet. The onboard camera was shooting aft about 4 o'clock and revealed alignment with the west taxiway inbound. The helicopter appeared to be about 15/20 feet above ground level. Just north of the Helinet ramp, the helicopter started a left climbing turn towards the hangars continuing into one or more 360 degrees turns. Subsequently, the main rotor blades contacted the asphalt ramp, and 21 feet beyond, the left side of the fuselage and nose section contacted the ramp, rupturing the fuel system. A postcrash fire occurred in fuel that had drained away from the fuselage into a low area of the ramp. PERSONNEL INFORMATION The commercial pilot held a rotorcraft-helicopter and a flight instructor for rotorcraft-helicopter rating. At the pilot's last documented first-class flight physical dated November 30, 1999, the pilot reported a total flight time of 1,557 hours with 500 hours in the last 6 months. The pilot attended an American Eurocopter ground and flight training program January 3, 2000. The flight experience that she reported to the training facility was: helicopter, 1,300 hours; turbine, 900 hours; and Astar, 30 flight hours. On January 5, 2000, she was awarded a certificate of achievement of Transition Ground School in the AS350 helicopter. On January 7, 2000, she was issued a certificate of achievement, having received 3 flight hours of Transition Flight Training in the AS350 helicopter. According to operator records, as of March 22, 2000, the pilot had 1,635 total helicopter hours, with 1,110 hours turbine helicopter time and 415 AS350 hours. At the time of the accident the pilot reported a total of 1,661 helicopter hours. AIRCRAFT INFORMATION On the evening of the accident, and prior to Safety Board arrival, an on-scene examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed a broken hydraulic pump drive belt, part number 704A33690004. The inspector removed the belt from the engine compartment and took possession of it. During the on-scene Safety Board examination, the Board requested the belt be returned to the Safety Board investigator. The location and rotational direction of the belt orientation was requested of the FAA inspector. He reported that the belt was lying loose in the compartment covered with water from the fire department coverage of the area. He said rotational direction could not be determined and he took possession to protect the evidence. According to maintenance records, a new hydraulic pump belt was replaced, along with a spare, on February 2, 2000, at 8,117.5 hours. The belt has a 600-hour life limit. Records also documented the hydraulic pump replacement with a new pump at 8,247.4 hours on February 24, 2000. The hydraulic pump pulley drive assembly was separated from the hydraulic pump and it was rotated by hand on scene. An amount of resistance to turning was noted. In the opinion of maintenance personnel at the accident site, the bearing was in a state of seizure. Grease was observed outside of the pulley drive sealed bearing housing opposite the splined drive end. According to the FAA approved maintenance manual, neither the hydraulic pump nor the drive pulley bearing have life limits, they are an on-condition replacement item. The on-condition inspection procedure is not detailed in the maintenance manual and it does not call for separation of the pump from the pulley assembly to get a rotational feel for the bearings condition. At the time of the accident, and according to the Hobbs meter, the helicopter had accumulated about 8,382.6 total flight hours. The most recent 100-hour inspection occurred on February 24, 2000, at 8,247.4 hours. An examination of the Eurocopter flight manual revealed an incomplete revision file with missing and misplaced pages. The last documented weight and balance was dated May 8, 1998. A pilot briefing room computer indicated a weight and balance not supported by flight manual information. No equipment list was located in the flight manual. A pine wood box, broken into several pieces with exposed nails measured 26x12x11 inches, with three shelves and separators, was found in the wreckage. The operator indicated the box had occupied a position between the rear seats. Its purpose was to contain books, videotapes, and miscellaneous items for news media charter customers' camera operators. There was no maintenance documentation that authorized the installation of the box in the helicopter. Examination of another operator's helicopter revealed a similar box for use by a camera operator. The box was designed to be restrained in the helicopter with a seat belt looped through a cutout in the box. The box was found unrestrained. EUROCOPTER FLIGHT MANUAL The flight manual addressed the malfunction that occurred on the accident flight as follows: According to the Eurocopter Flight Manual for the AS350B, Section 3, Emergency Procedures: Hydraulics; Section 3, Emergency Procedures HYDRAULICS "Servo-Control System Failure" "The pressure stored in the accumulators allows sufficient time to reach the "refuge" area with hydraulic servo-assistance." Warning of the pressure drop is confirmed by sounding of the horn in the cabin. NOTE: There are no accumulators in the yaw servo circuit." According to a Eurocopter representative, there is 30 to 45 seconds of accumulator assistance depending on the accumulator charge and control inputs. PILOT ACTION (In Flight) "Calmly reduce collective pitch and adjust the airspeed to between 40 and 60 knots in level flight. Cut off the hydraulic pressure, using collective lever pushbutton." METEOROLOGICAL INFORMATION At 2220, the Van Nuys weather was: wind 130 degrees at 4 knots; visibility 10 miles; scattered clouds at 19,000 feet; temperature 55 degrees Fahrenheit; dew point 48 degrees Fahrenheit; and the altimeter was 30.10 inHg. The Van Nuys Control Tower provided additional wind information to the helicopters during the approach to the airport. Approaching the freeway interchange the wind was given as 100 degrees at 4 miles per hour. Approaching the runway threshold the wind was given as 090 degrees at 5 miles per hour. WRECKAGE AND IMPACT INFORMATION The Safety Board examined the wreckage on scene located on the Rotorcraft/Helinet helipads. The helicopter was lying on the left side. The first point of contact was noted on the asphalt ramp. Four gashes were found about 20 feet from the fuselage. In the gashes were found rotor blade tip weights, stainless steel leading edge sections, and blue paint transfers matching the blue rotor blade color. About 21 feet beyond the rotor blade gashes were found the red navigation light lens, a left door handle, and metal scraping signatures matching left side door and fuselage material. The fuselage was found about 20 feet, on an azimuth of 230 degrees, from the fuel spray; it was facing 180 degrees magnetic. TESTS AND RESEARCH The pulley bearing is a sealed assembly using grease with a temperature range of -20 deg. C, to +100 deg. C, (212F). No grease life limit was noted. According to helicopter records, the bearing was an original part with about 8,382 total operating hours over about 15 years. ADDITIONAL INFORMATION The FAA accident/incident database was queried for hydraulic system failures. According to the reported database, 14 belts failed, 4 pulley bearings failed, 3 pumps failed, and 12 spline couplings sheared. On April 11, 2000, the Safety Board investigator attended a Eurocopter ground school training class on the hydraulic system and emergency procedure associated with it at the Texas facility. Emphasis was on the ease of control with hydraulic failure. A hypothetical question was asked of the ground school instructor. During an out of ground effect hover, if you lose hydraulics what would be the procedure to follow. He stated that as with any emergency you should land as soon as practical, and you would use your accumulator pressure remaining to establish your airspeed 40 to 60 knots, to a point of landing using a run-on-landing. An example was given of a typical hydraulic system failure at cruise flight, at which point you would lose yaw control boost. The procedure is to utilize the remaining accumulator pressure for pitch and lateral control to slow down to an easier manual control speed of 40 to 60 knots, and then punch off the hydraulics with the button mounted on the collective pitch control prior to asymmetric accumulator pressure loss. There is no accumulator in the yaw servo system. The remaining accumulator's pressure after pump failure is not addressed in the flight manual. Eurocopter representatives stated that it depends on the control inputs and accumulator's charge as to the remaining time, after failure, and may average 20 to 45 seconds of boost. If the accumulators were allowed to lose total pressure it would not happen simultaneously, and as a result, would cause unequal control inputs until they both went flat reverting to total manual control. The individual pilot body strengths for flying with no hydraulic boost were not discussed in the class. The pilot stature question was raised as to the pedal positions and the pilots leg lengths. The accident pilot was known to frequently fly with the pedals reversed or leaning aft. They were found in the forward position at the accident site, as was the pilot seat. According to Eurocopter personnel, full-sustained pedal control input can be a problem with short stature pilots. The accident pilot, according to the last flight physical, weighs 108 pounds and is 5 foot 1 inch tall. During the same visit, the hydraulic pump drive pulley assembly was examined and disassembled for bearing removal. The bearing was found to be powder dry with fragmented ball cages. Fragments were jamming the balls in the race. A black greasy type material was found outside the sealed bearing housing aft end. The Safety Board took possession of the hydraulic pump, belt, and drive pulley assembly, only. The parts were released back to the insurance company representative on August 10, 2000.
the pilot's failure to land as soon as practical and to utilize the available accumulator pressure to transition from hover to flight. Contributing to the accident was the pilot's physical stature and strength, and the inadequate and incomplete emergency training and flight manual information.
Source: NTSB Aviation Accident Database
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