LAX02FA281

the pilot's failure to maintain an adequate airspeed and main rotor rpm during the landing approach as prescribed in the hydraulic pump failure emergency procedures found in the rotorcraft flight manual, thus resulting in a loss of control of the aircraft and the subsequent crash. Contributing to the accident was the failure of the hydraulic pump due to excessive coupling spline wear which was caused by the application of insufficient lubrication by the operator's maintenance personnel during pump installation and the improper manufacturing of the couple sleeve.

The helicopter landed hard following a loss of directional control during a precautionary landing after a hydraulic system failure, with the main rotor blades cutting off the tail boom. This was a tour flight that was en route back to the departure airport when a complete hydraulic system failure occurred and the pilot decided to make a precautionary landing at a nearby airport. He had planned on conducting a run-on landing; however, during the approach the airspeed dropped to 30 knots. The helicopter's nose dropped and it started to spin to the left. The pilot pulled back on the cyclic enough to get the nose up; however, forward airspeed continued to decay and the rotation rate increased. The pilot said that the flight controls were not responding, and he believed the only way to stop or slow the rotation was to shutdown the engine. The helicopter completed two revolutions before it impacted the ground in a nose level attitude, 180 degrees from its original direction of travel. A witness to the accident reported the altitude of the helicopter as it began to spin was about 30-50 feet above the ground and he saw the main rotor blades cone upward as it fell to the ground. For a hydraulics failure, Federal Aviation Administration approved flight manual required the pilot to reduce the collective pitch and adjust the airspeed between 40 to 60 knots in level flight. The pilot was then instructed to cut off the hydraulic pressure by activating the collective lever pushbutton, and to make a flat approach over a clear landing area and land with forward speed. During examination of the hydraulic pump, investigators noted that the coupling sleeve splines were worn beyond serviceable limits. They also noted the general condition as rust colored, and no lubrication was found inside the pump housing or coupling sleeve splines. A company maintenance work order contained a serviceable tag for the hydraulic pump assembly. The serviceable tag that the operator's maintenance personnel wrote said that the hydraulic pump was "inspected, cleaned filter, new O rings installed on connections, inspected coupling, new pump assembled." The maintenance records also revealed that the assembled hydraulic pump was installed 15 days prior to the accident and had been in service for 74.6 hours when it failed. A metallurgical examination of the hydraulic pump revealed that it had failed due to the wearing away of the splines on the coupling sleeves. The wear was due to insufficient lubrication and soft splines on both coupling sleeves. The failure mode was assisted by an increase in internal rotational resistance at operating temperatures. The hardness testing indicated that the case hardened layer on the splines was not deep enough and the hardness, within the layer, was slightly below the specified range. The inner surfaces of the gear bearings displayed rubbed areas, consistent with hard contact, and areas of bluing, consistent with elevated temperatures. Examination of the coupling sleeves revealed a total loss of inwardly protruding spline material and hardness below the design requirements. The manufacturer's maintenance manual requires that the pump drive shaft, coupling sleeves, and bearing be packed with "abundant" grease during assembly. The examination found only a trace amount of grease in the coupling sleeves that did not satisfy the "abundant" requirement specified in the manufacturer's maintenance manual. There was rust on the front retaining rings and bearings, which indicated that there was insufficient grease in the splines to retain it or lubricate the splines.

HISTORY OF FLIGHT On September 11, 2002, at 1700 mountain standard time, an Aerospatiale AS350BA, N357NT, experienced a hydraulic failure during cruise flight and landed hard while making a precautionary landing at the Grand Canyon West Airport (1G4), Peach Springs, Arizona. Heli-USA Airways, Inc., operated the helicopter under the provisions of 14 CFR Part 135 as a tour flight. The helicopter sustained substantial damage. The pilot and five passengers were not injured. A sixth passenger sustained minor injuries. Day visual meteorological conditions prevailed for the tour flight over the Grand Canyon, and a company visual flight rules (VFR) flight plan had been filed. The flight departed the McCarran International Airport (LAS), Las Vegas, Nevada, about 1600. The flight was returning to LAS when the hydraulic failure occurred. According to the operator, the flight was returning to LAS when the helicopter had a "complete" hydraulic failure. The pilot was in the vicinity of Peach Springs Airport, and made the decision to make a precautionary landing. The helicopter landed hard, the main rotor blades flexed down and cut off the tail boom. According to the pilot's written statement, the flight to the Grand Canyon was uneventful. He made a radio call indicating that he was crossing the Grand Wash Cliffs area heading towards the Bat Towers. Five miles before entering the canyon he heard an aural alarm and saw that the hydraulic light was illuminated on the caution panel indicating a hydraulic failure. The airspeed was at 100 knots so he slowed the helicopter down between 40 to 60 knots per the recommended procedures, and turned off the caution horn using the button on the systems control console. After turning the helicopter towards the Peach Springs Airport, he depressed the hydraulic cutoff button on the collective control. During the approach he reported making his radio calls to the airport traffic, as well as coordinating with a sister ship to transport his passengers back to the operator's facility after landing. The pilot informed his passengers of the mechanical problems and noted no additional issues with the flight to the airport. He indicated that the hydraulic off indications were "felt" in the flight controls, and intended to do a run on landing in the new concrete landing/parking ramp area on the field. He reported that everything was normal until the helicopter was about 25 feet short of the ramp area. As he continued the approach, the flight controls increased in stiffness. He noted the airspeed was now 30 knots, and about 10 feet before the ramp at an altitude of 15 to 25 feet above ground level (agl). The nose pitched down, and the helicopter started to rotate. He pulled back on the cyclic enough to get the nose back up, which slowed the helicopter more but increased the rotation speed. The pilot thought they made two complete rotations, and reported that the flight controls were not responding. In order to slow or stop the rotation of the helicopter, he "cut off" the engine. The rotation slowed, and the helicopter started to settle to the ground. The pilot attempted to keep the helicopter in a level attitude, and it impacted in a near vertical descent from about 10 to 20 feet agl. The helicopter came to rest facing 180 degrees from its original direction of travel. The pilot reported that one of the passenger's feet had become trapped under the helicopter during the accident sequence. Airport personnel and pilot's from other companies assisted with pushing the helicopter up in order to remove the passenger's foot; there were no other injuries. In an interview with the National Transportation Safety Board investigator-in-charge (IIC), the pilot reported that the flight was about 3 minutes from the airport when he heard the aural caution horn and saw the hydraulic light illuminate. He also recalled that the passenger seated behind him was over 6 feet tall. The passenger's foot had been extended all of the way forward, resting by the pilot's side door, and had become trapped during the accident sequence. The pilot reported that the helicopter made two full revolutions to the right, and he had in full left pedal. He also reported that he had landed with a 4-knot tailwind. A witness to the accident (a company helicopter tour pilot) submitted a written statement to the Federal Aviation Administration (FAA). He reported that he was at 1G4 refueling his helicopter when he heard the accident pilot radio and that he had experienced a complete hydraulic failure. The witness asked where the accident pilot intended to land the helicopter, to which the pilot replied that he was headed for the large parking apron located on the northeast side of the runway. The witness reported that the helicopter was heading in a southerly direction. He observed the helicopter approach the landing area and said it was a little fast, between 40-55 knots. As the helicopter made its final approach to the parking apron, it was still a little bit high. The helicopter started to pitch up with a slow roll to the left. The witness reported that the helicopter's nose pitched down, all the while doing a complete 360-degree turn to the left. He estimated the helicopter's altitude between 30-50 feet. The witness began yelling on the radio for the accident pilot to get the nose of the helicopter up and not let it strike the ground in a nose down attitude. After completing the 360-degree turn, the witness reported that the helicopter had lost altitude in the left turn, the nose was slowly starting to pitch back to level flight, and the main rotor blades were starting to slow down. He reported that he could see the main rotor blades starting to cone in an upward direction, an indication to him that the main rotor blades were starting to slow down. The helicopter impacted the ground in a level attitude, and was covered by a large dust cloud. The witness could not see anything for about 10-15 seconds. He shut down the engine of his helicopter and ran towards the accident helicopter. When he was able to see the helicopter again, he noted that the tailboom had separated and was lying near the right side of the fuselage. He then assisted with the welfare of the passengers on the accident helicopter. PERSONNEL INFORMATION A review of the FAA airman records revealed that the pilot held a commercial pilot certificate with helicopter and instrument helicopter ratings. The pilot also held a mechanic certificate with ratings for airframe and powerplant. The pilot held a second-class medical certificate issued on August 28, 2002. It had no limitations or waivers. The pilot reported his total flight time as 4,025 hours, with 1,785 hours in the accident make and model. He had logged 134 hours in the last 90 days, and 21.6 hours in the last 30 days. According to personnel records obtained from the operator, the pilot had flown 2.3 hours on the day of the accident. The operator had employed the pilot since 2000. At the time of the accident he was the Assistant Director of Operations, as well as a company flight instructor and mechanic. AIRCRAFT INFORMATION The helicopter, serial number 1549, was originally issued a standard airworthiness certificate in 1987, as an Aerospatiale AS350B, but was converted to a BA and issued a standard airworthiness certificate on May 9, 2000. A review of the helicopter's daily flight logbook revealed a total airframe time of 8,387.7 hours at the last 100-hour inspection, completed on August 28, 2002. The airframe total time at the time of the accident was 8,451.7 hours. A Turbomeca Arriel 1B engine, serial number 4474, was installed on the helicopter. The engine total time was 8,824.5 hours at the last 100-hour inspection dated August 28, 2002. The engine had accrued 2,830.7 hours since overhaul, and 74.6 hours since the last 100-hour inspection.