NYC07MA073
NYC07MA073

HISTORY OF FLIGHT

On March 8, 2007, at 1502 Hawaii standard time, an Aerospatiale AS350BA helicopter, N354NT, operated by Heli-USA Airways, Inc., was substantially damaged when it collided with terrain following a loss of control while landing at the Princeville Airport (HI01), Princeville, Hawaii. The certificated airline transport pilot and three passengers were killed, and three passengers were seriously injured. Visual meteorological conditions prevailed for the local air tour flight that departed the Princeville Airport about 1415, and was conducted under 14 Code of Federal Regulations (CFR) Part 135.

According to the company dispatcher, the helicopter departed for a 45-minute sightseeing flight. When the pilot contacted the company base by radio about 1455, the dispatcher anticipated a routine radio call announcing his return. Instead, the pilot announced, "I'm having hydraulic problems, and I'm probably going to have to do a run-on landing." The dispatcher took her hand-held radio, ran to the hangar area, and notified the base operator and the maintenance supervisor of the pilot's intentions. She stated that as the conversation with the pilot continued, the language he used to describe his situation changed from "hydraulic problem" to "hydraulic failure." She continued to monitor the frequency as the helicopter neared the airport. As the helicopter approached the ground, she heard the pilot state, "Okay we're done." Then, the sound of the rotor changed pitch and the helicopter impacted the ground.

In interviews, several employees of the company explained how they prepared for the helicopter's arrival and heard it approaching. Some of the employees saw the helicopter "low" over the approach end of the runway, as they stood at base operations near the departure end of the runway. The helicopter then disappeared from their view, and shortly thereafter, they heard the sounds of impact.

Another witness, who worked at the terminal building at the center of the airport and had an unobstructed view of the helicopter through her office window, watched the helicopter approach. She noticed that the helicopter was not approaching the runway faster than usual, but it was flying lower than usual. The helicopter slowed over the runway at less than 10 feet above the ground, then turned slowly towards the grassy area on the left side of the runway. The witness wondered what the helicopter was doing, because the helicopter was moving slowly in a level attitude seeming as though it would land in the grass. Then, "...all of a sudden, the nose went down and [the helicopter] hit the ground." She described the entire series of events as happening "slowly." When asked about the landing gear floats, the witness stated that they were not deployed prior to the accident.

PERSONNEL INFORMATION

The pilot-in-command, age 59, was current and qualified to fly the accident helicopter in accordance with CFR Parts 135 and 91. A review of Federal Aviation Administration (FAA) airman records revealed that the pilot held an airline transport pilot certificate with a rotorcraft-helicopter rating, a commercial pilot certificate with a rotorcraft-helicopter rating, and a rotorcraft-helicopter flight instructor certificate. The pilot had accrued 10,471 total hours of flight experience, with about 3,500 hours in the accident make and model helicopter.

The airline transport pilot certificate was issued on August 20, 1977; the commercial certificate was issued on November 19, 1971 and the flight instructor certificate was issued on August 10, 1975. The original issuance of the FAA commercial pilot certificate was based on the pilot's previous military flight training and experience.

The pilot's most recent FAA second-class medical certificate was issued on January 24, 2007. The certificate carried a limitation that required the pilot to have correcting lenses available for near vision correction.

The pilot completed primary helicopter flight training with the U.S. Army in September of 1968. The primary flight training was conducted in a TH-55A Osage (Hughes Model 292). He later flew combat missions, and was an instructor in the UH-1 Iroquois.

A copy of the pilot's resume was obtained and reviewed. The following synopsis is a chronological summary of the pilot's employment history as a helicopter pilot:

1967 - 1971 Pilot/Instructor US Army
1975 - 1977 Pilot Bell Helicopters - Instructor (Esfahan, Iran)
1977 - 1980 Pilot Rocky Mountain Helicopters - EMS operations
1980 - 1981 Pilot Windward Helicopters - Oil support and external load
1982 - 2000 Pilot Rocky Mountain Helicopters - EMS Ops and Safety Manager
2004 - 2007 Pilot Heli USA Airways, Inc. - Air tour operations

The pilot's most recent Airman Competency/Proficiency Check was successfully completed on February 25, 2007. The pilot was also a company check airman per Special Federal Aviation Regulation 71, "Special Operating Rules for Air Tour Operations in the State of Hawaii."

HELICOPTER INFORMATION

The Aerospatiale AS350BA helicopter was powered by a single Turbomeca Arriel 1B turboshaft engine, with a three bladed main rotor system, and a conventional two bladed tail rotor for anti-torque and heading control. The helicopter had a seating capacity of 6 passengers plus a pilot and had 2 doors on each side of the helicopter.

The helicopter was manufactured in France in 1979. The AS350 series helicopters were made by Aerospatiale, Inc., a French company that later changed its name to Eurocopter, Inc., with a merger of Aerospatiale and Messerschmitt-Boelkow-Blohm (MBB), a German helicopter company.

The helicopter had accrued 21,706 total hours of operation and its most recent 100-hour inspection was completed on February 22, 2007, at 21,642 hours. An engine change was performed on February 28, 2007, at 21,665 aircraft hours.

A postaccident weight and balance estimate conducted by Eurocopter using the published weights of the pilot (145 pounds), a fuel load of 183 pounds, and a combined passenger weight of 1,085 pounds indicated that, at the time of the accident, the helicopter's approximate weight was 4,397 pounds, which was less than the certificated maximum allowable gross weight limit of 4,630 pounds.

Company Maintenance Program

The company was authorized by the FAA to conduct CFR Part 135 flight operations and maintenance in accordance with its FAA issued operations specifications (ops specs). The ops specs allowed the company to conduct maintenance on its helicopters as prescribed by the original equipment manufacturer (OEM) maintenance programs and were tracked by a computer database.

The company maintained its helicopters in accordance with a maintenance program that consisted of regularly scheduled inspections, component changes, parts replacements, heavy checks (such as 100 or 500 hour inspections), unscheduled maintenance, maintenance check flights after specific types of maintenance, such as flight controls, hydraulic servos, main/tail rotor blade replacement and engine changes. The accident helicopter was maintained using compact disks (CDs) provided by Eurocopter and Turbomeca.

The company General Operating Manual (GOM) was an FAA accepted, company written manual of standard operating procedures. Chapter 13 of the GOM outlined maintenance requirements, mechanics responsibilities, instructions for training of company mechanics, as well as a list of Required Inspection Items (RII). The RIIs called for separate inspections and signed logbook entries by mechanics that did not perform the actual work on the helicopter. The initial mechanic signed the logbook to indicate that the work was completed and a different mechanic stamped and signed the logbook to indicate that the work was inspected and approved for return to service.

Maintenance Record Review for the Accident Helicopter

A review of the maintenance logbook for the 30 days prior to the accident revealed that on February 9, 2007, (total time of 21,573.8 hours), the left lateral servo was removed and replaced; but no mechanic's RII stamp was present and neither was a maintenance check flight (ops checks) performed, as required by the GOM. On February 23, 2007, an ops check was entered in the helicopter logbook after completion of the most recent 100-hour heavy check inspection prior to the accident; however, no test flight time was logged as required. Instead the next flight time entry was for a revenue flight. The aircraft had accumulated 21,642.7 flight hours at the last heavy check.

On February 28, 2007, the engine was removed and replaced with a serviceable overhauled engine. An ops check was performed on March 1, 2007 after the engine change and 0.2 hours was recorded for the flight time. According to the Eurocopter flight manual, a four-page procedure was required that included logbook entries. According to Eurocopter, this ops check typically takes between 1 to 2 hours to complete.

Maintenance Procedures

During the investigation, maintenance activities were observed at the Princeville base. Even though the Eurocopter Maintenance procedures mandated work cards, none were in use throughout the investigation period. In fact, the computer based CD programs were used only occasionally. The mechanics stated that they only viewed the computer CD programs when they were unsure of a particular procedure. The maintenance section of the Heli-USA GOM required the use of the latest edition of the Eurocopter Maintenance CD; however, the most current CD found at the Princeville base was 3 revisions out of date.

METEOROLOGICAL INFORMATION

At 1453, the weather reported at the Lihue International Airport (PHLI), Lihue, Hawaii, 15 miles southeast, included scattered clouds at 5,500 feet, and winds from 050 degrees at 13 knots. The temperature was 23 degrees Celsius, and the dew point was 12 degrees Celsius.

AIRPORT INFORMATION

The Princeville Airport (HI01) had one hard-surfaced asphalt runway, 5/23. Runway 5/23 was 3,560 feet long and 40 feet wide. The airport was approximately 3 miles east of Hanalei, Hawaii, at an elevation of 344 feet above mean sea level (msl).
The airport was privately owned and was used primarily for helicopter tour operations. The airport did not have an air traffic control tower and was not equipped with navigational aids.

FLIGHT RECORDERS

The helicopter was not equipped with either a cockpit voice recorder or a flight data recorder. Neither was required by Federal regulations.

WRECKAGE INFORMATION

The helicopter was examined at the site on March 10, 2007, and all major components were accounted for at the scene. The helicopter came to rest on its landing gear with the landing gear floats deployed, and fully inflated. The helicopter was located on the grass on the left side of runway 05, 1,657 feet beyond the approach end of the runway, and 105 feet left of centerline. A ground scar marked the start of the wreckage path 1,433 feet beyond the approach end of the runway, and 72 feet left of centerline. The wreckage path was 33 feet long, oriented about 348 degrees magnetic, and ended at the final resting site of the helicopter wreckage.

The helicopter came to rest facing 168 degrees magnetic, nearly opposite the direction of travel of its approach to the airport. The nose, instrument panel, cockpit, and the cabin area forward of the rear seats were destroyed by impact, and fragments of composite materials were scattered in a wide arc around the wreckage. The center section of the fuselage was largely intact, with the main transmission and engine in their respective locations.

The tailboom was partially attached to the fuselage via sheet metal, wires, and control cables. The remainder of the tailboom, the horizontal stabilizers, and the upper section of the vertical fin were intact. The lower section of the vertical fin and the tailskid were bent and wrinkled. Tail rotor control and drive train continuity were confirmed from where the tailboom partially separated from the fuselage back to the tail rotor. The tail rotor, tail rotor controls, tail rotor driveshaft, and tail rotor gearbox were all intact. The skin on the tail rotor paddles displayed rotational scoring near their tips.

Examination of the engine and transmission areas revealed no evidence of a preimpact fire, structural failure, fuel leak or oil leak. The engine mounts were slightly twisted, but the engine and main transmission remained in their mounts and connected by the main driveshaft. The main rotor drive shaft was ruptured approximately 3 inches from the power off-take of the transmission shaft. Both ends of the rupture exhibited torsion load deformation.

Examination of the engine revealed that the axial compressor wheel rotated freely, the wheel and blades were intact, and there were no signs of blade rub or rotational scarring. The power turbine wheel rotated freely, the power turbine wheel and blades were intact, and there were no signs of blade rub or rotational scarring. The short shaft was found separated from the reduction gearbox and exhibited signs of rotational scarring. The flexible coupling and triangular flange exhibited torsion load deformation.

The red, yellow and blue main rotor blades remained attached to the hub. The main rotor blade spars were bent and twisted, but complete to the tips. The core and skin material outboard of the first one-third of each blade was fractured and scattered around. The blue sleeve and star arm were fractured. The red star arm was fractured, but the sleeve remained attached. The yellow sleeve and star arm were intact. All three main rotor pitch change links remained attached, with the red link being slightly bent.

Control continuity could not be established from the cockpit aft to the mixing unit due to impact damage and crush deformation of the airframe. Control continuity was established from the mixing unit to the flight control servos. The swashplate, scissors, and sleeve assemblies were all intact.

The hydraulic reservoir was full, but the sight glass was fractured and seeping. The hydraulic pump was intact, with the drive belt attached. The lateral and fore and aft servos, and their respective accumulators and electro-valves were intact. The flight control servos were all attached at the non-rotating swashplate. The fore-and-aft servo and the right lateral servo were attached to the transmission.

Further examination revealed that the lower clevis of the left lateral servo was still attached to the transmission case, but was no longer attached to the servo. Closer examination revealed that the threads on the clevis, as well as the threads on the inner diameter of the servo, appeared undamaged. The jam nut, the lock washer, and the safety wire were still attached to the clevis threads, and free to rotate. The lock washer was worn, and its locking tang was missing. The clevis was then removed from the transmission case along with its associated servo, for further examination.

The hydraulic pump and drive assembly were removed as a unit. The pump, the lateral and fore and aft servos, their respective accumulators and electro-valves, the hydraulic distribution manifold, the tail rotor servo, as well as the hydraulic pump drive belt were all removed and forwarded to the National Transportation Safety Board Materials Laboratory in Washington, D.C. for further examination.

MEDICAL AND PATHOLOGICAL INFORMATION

The Office of Pathology at Wilcox Memorial Hospital, Lihue, Hawaii performed the post mortem examination on the pilot. The examination report indicated that the cause of death was a result of "multiple traumatic injuries."

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing of the pilot. Fluid and tissue specimens from the pilot tested negative for carbon monoxide, cyanide, ethanol, and drugs.

TESTS AND RESEARCH

On May 10, 2007, the engine was placed in a test cell at Turbomeca USA, Grand Prairie, Texas, for the purpose of a test run. Examination of the engine revealed no anomalies and the engine started immediately, and ran continuously at rated power.

All three main hydraulic servos were initially examined at the Safety Board's materials laboratory, and then shipped to Hawker-Pacific, Burbank, California for a more detailed physical inspection. No pre-existing failures or anomalies were noted during the inspection. Examination and functional testing of the hydraulic pump and drive revealed that the pump operated as designed. Detailed examination of the coupling sleeve revealed that it was lubricated as prescribed, but the grease was gray in color, had a hard texture, and analysis revealed that it was not the prescribed grease for that application.

The Safety Board Airworthiness Group conducted a series of torque tests on the right lateral, fore, and aft clevis/servo assemblies from the accident helicopter. It was found that a lack of torque of the servo attachment nut, coupled with a severely worn lock washer, would allow the servo to rotate off the clevis, resulting in a complete disengagement of the servo from its mounting clevis on the transmission. Under normal loads, the main hydraulic flight control servos experience a slight twisting motion that could contribute to the attachment nut losing torque, coming loose, thus allowing the servo to rotate off the clevis bolt (without the proper locking washer installed).

During interviews with company mechanics regarding the servo build-up procedures, the mechanics improperly cited a torque value prescribed in a service bulletin for the upper clevis, which was lower than the prescribed value cited in the maintenance manual for the lower clevis.

After the discovery of the disconnected left main lateral servo on the accident helicopter, Heli-USA examined the main flight control hydraulic servo connections on all their other aircraft. Heli-USA found that on aircraft N350NT, the lock washer on the left main lateral servo had a damaged and worn tang and that the servo extension exceeded allowable limits. The left main lateral servo extension measured 41 mm. The allowable limit is 38 mm. Lock washers were removed from the accident aircraft N354NT (3) , N350NT (2), and N359NT (3) respectively, and were shipped to the Safety Board Materials Laboratory in Washington, D.C. for further examination. Metallurgical examination of the lock washers revealed that the locking tangs on the washer from the left lateral servo on N354NT and the washer from the left lateral servo on N350NT were both reduced to a stub. The stubs showed features consistent with oscillatory wear. The inner diameter of each washer also displayed wear grooves consistent with the dimensions and pitch of the servo clevis threads.

Eurocopter TELEX 00000382, published March 28, 2007, along with FAA SAIB SW-07-22R1, published April 3, 2007, alerted operators of the potential for servo disconnect, and to inspect for clevis extension and worn washers. Except for a service difficulty report submitted by Heli-USA on August 3, 2007, that referenced another "worn" locking tang, neither Eurocopter nor the FAA received any notifications of extended servos, or worn or broken lock washers as a result of the TELEX or the SAIB.

All of the worn lock washers were found at Heli-USA's Hawaiian maintenance base only. There were none reported at Heli-USA's Las Vegas base of operations.

ADDITIONAL INFORMATION

Maintenance Training

Examination of training records for three mechanics stationed at Heli-USA's Princeville, Hawaii, base revealed that none of the mechanics had received any formal Eurocopter AS 350 maintenance training. During interviews, mechanics stated they received on-the-job training under the supervision of another company mechanic. The mechanics stated there were no formal training records that documented subjects covered. However, their training records indicated that each mechanic had received the CFR Part 135 mandated company training that concerned the GOM, the company's paperwork, and their maintenance duties and responsibilities.

Emergency Procedures

According to the Eurocopter AS350 Flight Manual, Hydraulic Power System Failure Training section, after completion of the immediate action items and adjusting to the "recommended safety speed" of between 40 to 60 knots, the pilot should, "Make a flat approach, nose into the wind, and perform a no-hover slight running landing at low speed (10 kt are sufficient)." A Comments section adds, "Transition to hover flight or flight with tail wind, will cause a change in the direction of the control load on the cyclic stick in the fore and aft direction. If the pilot does not respond quickly enough to this phenomenon, it will result in a hard landing."

The pilot was initially trained by, and was an instructor pilot for, the U.S. Army. According to the Aircrew Training Manual for the UH-1 helicopter (TC-1-211), after completion of the immediate action items for a hydraulic failure, "The [pilot on the controls] should progressively decrease the rate of descent and rate of closure to effect a touchdown at or slightly above [effective translational lift] within the first one-third of the landing area."

(This report was modified on June 16, 2009)

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