FEATHER FALLS, CA, USA
N8395F
Hughes 369D
While conducting external load operations, the aircraft was orbiting east of a logging pickup site when the sling load contacted trees and terrain near a ridge. Weather at the time was clear with light winds. The helicopter was seen shaking and oscillating followed by a flat spin with the sling line still visibly attached. A radio call asking what was wrong was made with no reply. The first persons to reach the accident site found the belly hook and line still engaged. Evidence of freshly broken tree limbs and branches was found back along the flight path. Deposits of woody debris were also noted on sections of the lines and load. No discrepancies were found with the belly hook.
HISTORY OF FLIGHT On December 20, 1995, at 0925 hours Pacific standard time, a Hughes 369D, N8395F, collided with trees and terrain while maneuvering near Feather Falls, California. The aircraft was destroyed and the pilot, the sole occupant, received fatal injuries. The aircraft was being operated for external loads by Air, Inc., under 14 CFR Part 133, and was maintained under 14 CFR Part 135 when the accident occurred. The flight originated near Feather Falls at 0900 on the day of the accident. Visual meteorological conditions prevailed at the time and no flight plan had been filed. The helicopter was in the process of slinging a 700-pound load of choker cables from a log drop-off site back to a log pickup site. Ground witnesses at two log pickup sites had been in radio contact with the pilot minutes prior to the accident. The pilot asked them if they were ready for him to bring in another load of choker cables. They replied that they did not need any cables at that time. The pilot began to orbit to the right about 0.5 miles east of the log pickup sites and was downwind of a Sikorsky CH-54 helicopter which was hooking up to a load of logs at one of the sites. Witnesses on the ground described the weather at the accident site as clear with a 5- to 7-knot wind blowing down the canyon from the logging operation and in the direction of the orbiting aircraft. Two of the witnesses on the ground reported seeing the accident helicopter shaking and oscillating left and right, followed by a flat spin to the right with both sling lines still visible before it descended from view. During that sequence one of the witnesses made a radio call asking, "Robbie, what's wrong?" The transmission was monitored by other ground members of the logging operation; however, no one reported hearing any response from the pilot. Upon reaching the accident site, investigators found both lines, which were still connected to each other at the remote electrical hook, lying along the flight path (175-degree bearing) within about 100 feet of the main fuselage. The line was disengaged from the belly hook, but the line hook was still a few feet from the belly hook. The first witnesses to reach the accident site reported that when they arrived the belly hook and the line were still engaged. However, while rescue personnel were attempting to remove the pilot, one of the rescue personnel inadvertently bumped the mechanical release, opening the belly hook and releasing the line. The end of that line was found on the ground near the nose of the aircraft. About 600 feet back along the flight path, investigators found the first evidence of contact between the external load and the trees on the hilly terrain below. An 80-foot-tall tree near the top of a ridge was observed to have a visible break at its top. The 10-foot broken section from the tree was located about 100 feet further along the flight path. The broken section of tree exhibited fresh chaffing and scarring on its trunk with numerous smaller broken tree limbs and branches also lying in the vicinity. There was evidence that an object had been drug along the ground in the direction of the aircraft wreckage. Deposits of woody debris were noted on sections of the lines and on the bundles of choker cables. PERSONNEL INFORMATION The operator reported that the pilot completed his initial/new hire training on May 18, 1995. After each phase of training he was evaluated by the operator's chief pilot. His external load training was completed on May 14, 1995, in a Bell 204B. An additional external load check ride was given on October 20, 1995, in a Hughes 500D. Specifically, his external load qualifications included long line remote hook operations and mountain flying. A review of his training records revealed that he had completed all phases of his training successfully. The pilot also held an airframe and powerplant certificate and reported 17 years of maintenance experience on helicopters. Coworkers reported to the operator that the pilot generally displayed a friendly cooperative attitude. On the day of the accident he appeared to be in his usual friendly attitude without any discernible preoccupation or mood alteration. AIRCRAFT INFORMATION The aircraft experienced a tail rotor strike and subsequent salt water landing on June 10, 1992. It was repaired and put back into service by Chet Rasberry on April 5, 1994. It had been configured to conduct long line operations in support of an aerial logging operation. The last annual inspection was completed on July 1, 1995, using the McDonnell Douglas Helicopter Systems 100-hour inspection checklist. However, that same check list also directs the completion of all 300-hour inspections in order to satisfy the annual requirements. A review of the aircraft logbooks did not disclose any recurring deficiency or deferred maintenance items. A review of applicable airworthiness directives (ADs) and service notices (SNs) revealed 10 which were applicable but were not entered in the aircraft logbook. Included among them were: a tail rotor swashplate lockwasher inspection (AD), a tail rotor abrasion strip bonding inspection (AD), and a tail rotor abrasion strip modification (SN). The empty weight of the aircraft was last verified by the operator on October 12, 1995. The aircraft's gross weight at the time of the accident was within gross weight and center of gravity limitations. Specifically, the aircraft's task was to return sets of choker cables to ground crews who then prepared logs to be slung from the cutting location to a staging location where the logs were then loaded for surface transportation. The helicopter was equipped with a 150-foot sling line which was attached to the aircraft's cargo hook. The sling line was then connected to a 50-foot cable by means of a remote electrical hook positioned at the end of the sling line. The pilot was seated in the left seat for the external load operation. WRECKAGE AND IMPACT INFORMATION The aircraft was located at latitude 38.39 degrees north and longitude 121.08 degrees west. The aircraft's final position was on a magnetic bearing of 300 degrees resting on its nose in a near 90-degree nose down attitude. There was crushing and buckling visible on the forward canopy and cabin overhead canopy. The left front door was separated, while the right door was still attached and closed. The "A" frame assembly and the keel beam were intact and generally undamaged. The left forward cabin, including the canopy and door frames, revealed crushing and buckling. The static mast base plate was intact. The main transmission, static mast, rotor head, and main rotor drive shaft had all remained attached to the airframe. A crush line extended approximately from the lower left front door fuselage station (FS) 40 aft to FS 56, upward to FS 85 and then diagonally forward and laterally to the center of the canopy frame. The tail boom was separated at FS 255. There were numerous scars and breaks occurring in numerous 2- to 10-inch diameter trees along the final flight path and in the immediate impact site. The airframe itself showed numerous buckles along both sides and the belly. The left skid tube was separated in several places. An examination of all main rotor blades revealed extensive leading edge damage, as well as flapping and torsional bending. Both tail rotor blades were located and both blade roots were still in the blade grips, although one blade had separated. The tail rotor gearbox was still attached to the tail boom. The tail rotor drive shaft displayed breaks with "cork screw" deformation at several points between the transmission and the tail rotor gearbox. All tail boom and tail rotor components were located in the immediate vicinity of the final impact. The instrument panel and console were still attached to the airframe and did not exhibit any crushing or buckling. Several caution panel segment lights were recovered and submitted to the Safety Board's Material Laboratory for filament analysis. All cyclic, anti-torque, and collective controls were essentially undamaged forward of FS 78. The lateral and longitudinal control tubes located under the forward seats were intact and undamaged. The cyclic control system exhibited a separation between from the cyclic stick to the rotor head mixing assembly and stationary swashplate. The mixing assembly bellcrank and pitch change links also exhibited separations. The stationary and rotating swashplate were still attached to the upper mast and could be rotated on the static mast. The blue, yellow, red, white, and green pitch change links were separated and showed bending deformation at the fracture points. The main rotor elastomeric damper assemblies had varying degrees of damage: the blue was attached but bent up at the outboard clevis stud; the yellow was attached to the pitch housing while the outer clevis stud was bent and separated; the red was attached to pitch housing while the outer clevis stud was bent and separated; the white was separated at the pitch housing fitting; and the green was attached to the pitch housing while the outer clevis stud was bent and separated. The collective control system was separated at the upper rod near the bearing insert at FS 78. The anti-torque control system was separated with the aft tailboom during the breakup sequence. An inspection of the upper control system also revealed a separation at FS 78. The main rotor head was attached to the static mast and could be rotated freely. The main rotor pitch housing assemblies, including the yellow, red, green, and blue were attached and intact. The white assembly was separated. The main transmission case was intact with no visible damage. The oil sight showed the presence of oil without evidence of visible contamination. The input quill housing and tail rotor output shaft were attached and the transmission chip plug was free of metallic debris. The output shaft, main rotor drive shaft, and rotor head could all be rotated without binding through the static mast. The overrunning clutch was intact and functioned when the drive shaft was rotated. The engine to transmission drive shaft was intact and functioned when the engine or transmission was rotated. The tail rotor drive shaft was found torsionally twisted at FS 270. The Bendix couplings were installed and intact at both ends of the drive shaft. The drive shaft was separated at FS 256. The tail rotor transmission was intact and gearbox and hub assembly rotated freely in both directions. All five main rotor blades exhibited numerous bends and separations. The white blade was fractured at the outboard of the root fitting and showed several bends 4 feet from the root fitting. The blue blade was bent and folded in the lag direction 2.5 feet outboard of the root fitting. The outboard portion of the blade is also separated and the blade displayed lead and lag span bending. The yellow blade was separated at the outboard end of the root fitting. The trailing edge was missing and the blade revealed lead and lag span bending. The red blade was folded back at the outboard end of the root fitting. The green blade was wrapped around the static mast. The fuel cell remained intact after the accident sequence and the odor of fuel was noted when approaching the aircraft. There was no evidence found of a fuel leak or spill at any point during the on-site or off-site portions of the investigation. The fuel shutoff valve functioned, although its operation was stiff when moved toward the "open" position. The amount of fuel found in the fuel cell was above the level which would have activated the "20 minute" light. An examination of the 20 minute float revealed that the float switch was misaligned and would not illuminate the light regardless of the fuel level. The tail boom frame was twisted and separated at FS 257 in a torsional direction. There was no evidence of main rotor blade strikes on the tail boom. The vertical stabilizer was separated below the horizontal stabilizer. The upper portion demonstrated crushing and scarring while the lower portion was relatively undamaged. The horizontal stabilizer was intact and undamaged. There was no visible evidence of a malfunction identified during the on-site examination of the engine. The engine was removed from the airframe and transported to the manufacturer's facility for a further inspection and operational testing. At the manufacturer's facility, the engine was mounted in a test stand and started. After 10 minutes at ground idle, the engine was accelerated to takeoff power with no anomalies noted. A timed deceleration check was conducted followed by a series of snap back accelerations checks and a governor droop check. All checks met the manufacturer's prescribed parameters for a new engine except for horsepower. Horsepower was found to be just below minimum allowable limits while operating at normal cruise or takeoff power settings. The engine logbook could not be used to determine engine times and inspections since the log ended with a September 7, 1993 entry. Attempts to crosscheck the engine log with the aircraft logbook were unsuccessful. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was conducted by the Plumas County Coroner's Office. Toxicological samples were drawn by the coroner and submitted to the FAA Civil Aero Medical Institute (CAMI) for screening and analysis. CAMI reported the results of the screening were negative for all substances included in their protocol. (Toxicological results are appended to this report.) TESTS AND RESEARCH A fuel sample from the accident aircraft was obtained and submitted to Core Laboratories for analysis. The fuel was found to meet the specifications for Jet-A and was free of contaminants. Light bulb filaments from the master caution panel were obtained for the tail rotor transmission chip light, the engine chip light, and the generator out light and were submitted to the Safety Board's Materials Laboratory. None of the filaments showed evidence of stretching. (Metallurgist's Factual Report is appended to this report.) ADDITIONAL INFORMATION The emergency locator transmitter (ELT) was located on the ground immediately in front of the nose of the aircraft. There was no ELT signal reported in the vicinity at any time after the accident occurred. The aircraft was recovered by representatives of Plain Parts and transported to their storage facility in Pleasant Grove, California. The aircraft was released to a representative of the owner on June 11, 1996.
the pilot's failure to jettison his external load after it came in contact with trees and terrain. The pilot's failure to maintain altitude/clearance above trees and hilly terrain was a related factor.
Source: NTSB Aviation Accident Database
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