Hanalei, HI, USA
N11VQ
AIRBUS EC130
During an air tour flight, the helicopter was about 1/4 mile offshore at 1,450 ft mean sea level (msl) when the pilot heard the low rotor rpm warning horn. He immediately entered an autorotation and turned toward the beach. As he approached the shoreline at 374 ft msl, he made a sharp right turn to avoid large boulders in his intended landing area. The helicopter subsequently landed hard on the beach, bounced, and came to rest. Examination of the engine revealed that the main fuel injection pipe between the fuel valve assembly and the injection union was cracked and broken at the injection union B-nut connection. Subsequent engine test runs revealed that the starter-generator imparted a vibration into the engine that excited the fuel pipe to vibrate in resonance and ultimately fracture due to reverse bending fatigue at the flared end. The crack or fracture of the fuel pipe allowed pressurized fuel to escape, reducing fuel flow and pressure to the injection manifold below that which was required to sustain combustion, and resulted in the loss of engine power. The vibration imparted into the engine by the starter-generator remained below the global vibration limit for the entire engine, but was sufficient to excite the fuel pipe. Examination of the starter-generator revealed that the front bearing outer race and support exhibited signatures consistent with fretting and pronounced wear. This observed wear of the front bearing support allowed the armature to oscillate and impart a vibration into the engine frame. Further, the investigation was unable to determine when the vibration began and if the fatigue crack had already started at the time of the last inspection. Without a requirement to look at the front bearing and the shaft play, the operator would have no way to identify the vibration issue. Onboard video imagery recorded during the accident flight confirmed that the pilot's harness lap belt was positioned properly, low and tight across his hips. Of the six passengers onboard, four passengers' lap belt positioning were visible in recorded cabin imagery, and depicted that the lap belts were not tight across their hips and that the buckle was at or above their waists. Examination of the pilot's seat revealed vertical displacement consistent with a significant amount of vertical energy being absorbed by the seat during the hard landing. Two of the passenger seats displayed some vertical displacement, two displayed minimal vertical displacement, and two seats showed no vertical displacement. The seat displacement was directly related to the amount of vertical energy absorbed by the seat and to the severity of the occupant's injuries. The loose and out-of-position seatbelts most likely allowed the passengers' bodies to shift out of position on the seat before and during the hard landing and did not restrain the occupants in the proper position for the seat to absorb the vertical landing loads for which it was designed.
HISTORY OF FLIGHT On January 17, 2016, about 1432 Hawaii standard time (HST), an Airbus EC130 T2, N11VQ, was substantially damaged when it was involved in an accident near Hanalei, Hawaii. The commercial pilot and six passengers were seriously injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 135 air tour flight. The pilot reported that, about 25 minutes after departure for the sightseeing flight, the helicopter was about 1/4-mile offshore northwest of the Honopu Sea Arch between 1,300 ft and 1,400 ft mean sea level (msl) when he heard the low rotor rpm aural warning horn. He immediately entered an autorotation, turned toward the beach, and transmitted over the radio that he had an engine failure. As the helicopter approached the shoreline, he made a sharp, low-level right turn to the south to avoid large boulders in his intended landing area and subsequently landed hard on the beach. He applied the rotor brake to slow the rotor and noted that the engine was not running. The passengers began to exit the helicopter and he pulled the engine fuel cutoff. The first indication of an inflight loss of power was an uncommanded right yaw that occurred at 14:31:31. The first limit indicator (FLI) on the instrument console started to drop rapidly, followed by the GENE (generator) annunciator light illumination. The helicopter entered a 20° right turn toward the coastline. Five seconds later, the ENG P (engine oil pressure) annunciator light illuminated, followed by the FUEL P (fuel pressure) light and the helicopter returned to a nearly-level flight attitude. About 10 seconds later, the helicopter was passing through 600 ft at 85 knots. Rotor rpm had increased to 430. After about 11 seconds, the coastline became discernable and revealed a rocky, unsuitable landing area. The helicopter's altitude was about 350 ft and the rotor speed was 364 rpm. At 14:32:08, the helicopter had entered a 45° right bank, altitude was 275 ft, airspeed was zero, and the helicopter was maneuvering toward a sandy beach area. About 3 seconds later, the LIMIT (servo limit) light illuminated, the helicopter entered a near-level pitch attitude, airspeed was near zero, and rotor speed was around 200 rpm. Initial ground impact was at 14:32:13 and the rotorcraft was at rest at 14:32:15. AIRCRAFT INFORMATION The single-engine helicopter was configured for air tours with 6 passenger seats and a single pilot seat, and equipped with a skid mounted emergency flotation system. The pilot occupied the left front seat. Review of maintenance records showed that the helicopter was maintained in accordance with an FAA-approved aircraft inspection program (AAIP) which can differ from the maintenance program recommended by the manufacturer. The Hobbs meter read 692.7 hours immediately after the accident. The helicopter was equipped with an Appareo Vision 1000 flight data recorder and a Datatoys AirKnight HD4s video recorder system that had hard-mounted internal and external cameras for recording the tour for the customer. The rotorcraft flight manual listed the maximum gross weight of the helicopter as 5,512 lbs. Information provided by the operator indicated that the helicopter departed on the accident flight with a takeoff weight of 5,284 lbs. The helicopter would have consumed about 170 lbs (26 gal) of fuel during the flight. FLIGHT RECORDERS The helicopter had two flight recorder systems installed, an Appareo Vision 1000 small self-contained image, audio, and data recorder, and a Datatoys AirKnight HD4s airborne video recorder designed for helicopter tour applications. Data from both systems was recovered and reviewed by the NTSB Vehicle Recorders Laboratory. WRECKAGE AND IMPACT INFORMATION The helicopter landed hard onto Kalalau Beach, along the north shore of Kauai. While on the beach, sea water washed over the landing skids and cabin deck of the helicopter. The operator transported the helicopter from the landing site to their maintenance hangar in Lihue, Kauai. On January 25, 2016, technical representatives from Safran Helicopter Engines (Safran HE) and Airbus Helicopters under the oversight of an FAA inspector examined the helicopter at the hangar. During the examination, the engine's main fuel injection pipe between the fuel valve assembly and the injection union was found cracked and broken at the B-nut connection. A black, oily substance was observed around the interface between the engine magnetic seal and the starter-generator. The airframe sustained structural damage to the tail boom and cockpit floor. The engine, starter-generator, vehicle and engine management display (VEMD), digital engine condrol unit (DECU), and engine data recorder (EDR) were removed for further examination at the manufacturer's facility. The fractured fuel pipe was sent to the NTSB Materials Laboratory. On May 11, 2016, the NTSB investigator-in-charge (IIC) and technical representatives from Blue Hawaiian Helicopters, Air Methods Corporation (DBA Blue Hawaiian Helicopters), Airbus Helicopter and Zodiac Aerospace, examined the helicopter wreckage at the Lihue hangar. The tail skid was bent up into bottom of the fenestron and the bottom of the fairing displayed a 20-inch crack in the longitudinal direction. The tail boom was symmetrically buckled on the left and right sides at the intermediate structure attach point and had significant buckling at the bottom. The rear fenestron drive shaft support bracket displayed a slight buckle. The engine deck was slightly buckled aft of the rear engine support. Plastic deformation of the engine support in the aft direction was observed. The right transmission bay, transmission support rod, and lower rod end rivets had sheared along the support tube axis. The main gear box (MGB) right support rod was deflected 24 mm at the largest point (mid span). The right cargo bay had no noticeable buckling of the X-wall. The crashworthy fuel tank displayed no deformation or leaking of fuel. The cockpit center console's forward upper mount plate was buckled on the right side. The left MGB support rod rivet heads were sheared. The left cargo bay displayed buckling of the X-wall at the lower aft corner. The left firewall had buckled along the lower edge. There were two areas of slightly buckled skin indentations on the fuselage transition area. The helicopter sat with a 5° list to the right. The seats were documented and then removed from the helicopter. The seats were manufactured by Zodiac Seats France (ZSFR), part numbers 19820-02-00 (front, referred to as T198) and 28410-0400 (rear, referred to as T284). The helicopter cabin was scanned using a 3D handheld laser, and all the seats were laser scanned. Pitch & roll angles were similar for all the seats. Seat foam and upholstery had manufacturing labels from Aero Comfort Company, the seat labels did not display a technical standard order (TSO) compliance number. No external impacts to any of the seats was observed. All seat equipment was installed correctly, according to Airbus and Zodiac technical representatives. The following table documents the postaccident configuration of each seat. The stroke is the measured downward displacement of the seat as a result of vertical accelerations, and the fuses are metal links that release once a specified amount vertical force is experienced allowing the seat to stroke downwards (Note: Seat No. 3 is used in some configurations, but was not installed in the accident helicopter). Table 1 - Seat displacement measurements. SURVIVAL FACTORS Injuries Six of the seven helicopter occupants were diagnosed on the day of the accident with thoracolumbar compression fractures. The seventh was diagnosed several weeks later. With the exception of the occupant of seat No. 1 (who became paraplegic), the occupants remained neurologically intact. The occupants in seat Nos. 2 and 7 had fractures at multiple vertebral levels. The occupants in seat Nos. 1 and 2 both had sternal fractures. Helicopter Seat Design Both T198 and T284 seats consisted of a composite bucket affixed to a structural frame composing both the seat legs and seatback supports. The seatback supports contained energy absorbing features in order to meet the requirements referred to in 14 CFR sections 27.785, 27.561, and 27.562. Corrugated absorption devices and fuses were built into either side of seatback supports (total of two in each seat) to absorb energy in event of high vertical loading. The composite seat bucket was affixed to the seat frame on a set of tracks via two "bucket fixings" and plastic bushings (rollers). When subjected to high vertical loads, these features allowed the bucket to move downwards while the absorption devices deformed (i.e. stretched) and absorbed vertical energy. The undeformed dimension of the absorption devices was 10.7cm. Additionally, the seat foam and upholstery are considered part of the seat design and certification (SFR ETSO C127a). Zodiac Seats France reported to the BEA (Bureau d'Enquetes et d'Analyses pour la securitie de l'aviation civile) that the two models of seats installed in the helicopter were certified to Europe TSO C127a for dynamic conditions of a 30g downward test with the seat pitched upwards at 60°, and an 18.4g forward dynamic test both using a 170-pound anthropomorphic test device . Immediately before takeoff, the internal camera video recorded the passengers' seating position and the visible harness buckle location on those individuals. The helicopter seat designated numbers are as follows; the pilot seat in the front left, seat Nos. 1 and 2 were front center and right, respectively; seat Nos. 4, 5, 6, and 7 were the rear seats numbered right to left, sequentially. The pilot's harness lap belt was positioned below his waist and low across his hips. The harness buckle position on the passenger in seat No. 1 was positioned about mid abdomen. The seat No. 2 passenger's harness buckle was in the vicinity of his mid abdomen. The seat No. 4 passenger's left shoulder harness was visible, but all other harness features were obstructed. The seat No. 5 passenger's harness buckle appeared to rest slightly below mid abdomen. View of the seat No. 6 passenger's harness configuration was obstructed. The seat No. 7 passenger's harness buckle was above their mid abdomen. About 2 minutes before the beginning of the accident sequence, the AirKnight camera showed the passenger cabin view. The seat No. 1 passenger was leaning forward, her right shoulder harness was secured over the right shoulder, her left shoulder harness was not seen over the left shoulder but moved in concert with the right shoulder harness at the Y strap. The shoulder harness was moving consistent with the passenger's body movement, which was slightly leaned forward. The pilot's shoulder harness was in place. The pilot's left hand was forward and resting on an undetermined cockpit object. The seat No. 2 passenger was seated normally and wearing their shoulder harness. The seat No. 4 passenger was seen with the left shoulder harness clearly visible; their right shoulder harness was obstructed. The seat No. 5 passenger was seated normally and seen wearing both shoulder harnesses. The seat No. 6 passenger was taking a photograph at head level and had his body oriented to the right in the helicopter. The view of his harness position was obstructed. The seat No. 7 passenger was seated normally and was looking out the left side of the helicopter; both shoulder harnesses were visible. Immediately prior to initial ground impact, passenger 1 had moved her left hand off her left knee and neither of her hands were visible in the field of view. Her feet appeared to be flat against the rotorcraft's floor. The other passengers were not in the field of view of the camera, and therefore their body positions were not documented. Hard Landing Impact Analysis Airbus Helicopters used GPS, helicopter flight data recorded by the on-board Vision 1000 Flight Data Monitoring hardware, post-accident helicopter structural measurements, on-scene photos, and landing terrain plasticity (sand) to estimate landing attitude and impact forces experienced by the helicopter during the accident. The on-site documentation and the flight data were consistent in showing that the helicopter experienced two landing events, an initial landing followed by a bounce and a second landing. Data showed that immediately before ground impact the helicopter was in a 10° right bank, 3.6° nose up, forward velocity was 13.2 m/s and vertical velocity was 12.2 m/s. A Mecano simulation was created modeling these conditions. The results of the simulation estimated that the initial landing impact was 24g in the vertical axis, 9g in the horizontal axis, and 4g in the lateral axis. The second landing forces were estimated as 19g vertically, 7g horizontally, and 1 g laterally. Based on the low level of rotational acceleration of the center of gravity, all occupants experienced about the same level of impact forces. Harness / Seat Belt Positioning on Occupant Section 4.3 of the EC 130 B4 Flight Manual is the Start Up Checklist. Under the subtitle 4.3.1 Engine Prestart Check is: "- Seats and control pedals…………...ADJUSTED" "- Seat belts ……………………………FASTENED" There is no information in the flight manual describing the proper use or positioning of the seat belt on occupants. Blue Hawaiian Helicopters provided a 6-minute instructional and safety video for the passengers to watch before flight . The seat belt instruction portion of the video simply states to pull the waist straps until snug and showed a passenger with the buckle positioned over her navel. The operator had an employee escort the passengers to the helicopter. They then would assist the passengers in entering the helicopter and fastening the four-point harness. FAA Medical Facts for Pilots, publication AM-400-90/2, Seat Belts and Shoulder Harnesses (2004), states: "The restraint should be adjusted as tightly as your comfort will permit to minimize potential injuries. The safety belt should be placed low on your hipbones so that belt loads will be taken by the strong skeleton of your body. If the safety belt is improperly positioned on your abdomen, it can cause internal injuries." "…When it is tight about your hips, the safety belt should be positioned so that it makes about 55 degrees with the center of the airplane. This allows it to resist the upward pull of the shoulder belts, reducing the risk of internal injury." TESTS & RESEARCH Blue Hawaiian Fleet Survey of Fuel Pipe The Air Methods Director of Engineering and Reliability issued a Fleet Campaign Directive, Inspection of fuel pipe B-nut checking for torques and leakage. Air Methods Corporation owns and operates Blue Hawaiian Helicopters. The survey of the Blue Hawaiian fleet of EC-130 helicopters did not identify any loose fuel pipe B-nuts or leakage of the fuel pipe. Engine Exams and Tests On February 4, 2016, the NTSB IIC with technical representatives from the FAA, Safran Helicopter Engines, Airbus Helicopters, and party representative from Blue Hawaiian Helicopters examined the engine and associated components at the Safran Helicopter Engines facility in Grand Prairie, Texas. The engine was visually examined. No external damage was noted. The compressor and turbine turned freely by hand. Compressed air was passed through the engine to clear out any debris. A borescope examination of the compressor, combustion section and the high-pressure turbine, revealed no anomalies. The broken fuel pipe had been removed during the initial on-scene examination. A replacement fuel pipe was installed on the engine. The starter-generator was removed and a black oil/grease substance was observed on the starter-generator engine side mounting flange and on the forward face of the starter-generator. A sample of the oil/grease substance was taken for further examination. The starter-generator (Thales SN: 5493) was visually examined. The rotor's splined shaft rotated freely by hand an
The fatigue failure of the engine fuel pipe as a result of vibration caused by a worn starter-generator front bearing support, which excited the fuel pipe and caused it to oscillate at a resonant frequency, and a subsequent loss of engine power due to fuel starvation. Contributing to the severity of passenger injuries was the improper positioning of the passengers' seat belts.
Source: NTSB Aviation Accident Database
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