Whiteriver, AZ, USA
N6184D
Bell 206L-3
During a right turn to return to a mountain landing site, the helicopter began to spin and struck trees. The flight's mission was to insert a helicopter fire attack crew at the location of a wildfire. The landing zone (LZ) closest to the fire was in a small area surrounded by trees. The density altitude was calculated to be 11,968 feet. The pilot first landed at a meadow about a mile away and off-loaded two fire fighters, then proceeded to the LZ, and dropped off the one remaining fire fighter and tools. He returned to the meadow, where he picked up the additional crewmembers. The flight returned to the landing site, overflew the LZ and continued up the drainage before making a right turn back towards the LZ. One witness seated in the front left seat noted that on the first takeoff from the meadow the torque gauge was at 100 percent and the helicopter was "hard to get off the ground" and the climb out was slow and labored. On the return flight to the LZ, the first fire fighter dropped at the LZ saw that the helicopter was flying slowly about 20 feet above the tree line. He believed they would land with the wind; however, the pilot flew the helicopter past the LZ and continued up the drainage. A surviving witness in the left front seat noted that the torque gauge read 100 percent. As the pilot initiated the right turn to return the LZ, the torque reading went from 100 to 105 and then 110 percent. He asked the pilot if the tail rotor was going to stall, but received no response. The witness noted that the airspeed gauge read zero. At that point the pilot started to rapidly move the collective, cyclic, and "his feet." The helicopter then spun two times to the right. Both a ground witness and a rescue flight crew noted that the LZ had a slope to it and was located in very tight area, with reported winds southwesterly between 2-4 knots. During the on-scene investigation, investigators noted that the compressor blades in the engine were folded opposite the direction of rotation and that tree fibers had been ingested by the compressor impellor, a condition indicative an operational engine at high power at the time of impact. The engine teardown revealed that additional tree fibers were found throughout the gas path from the compressor section through to the combustion and exhaust sections. There were no other discrepancies noted with the airframe or engine that would have precluded normal operation.
HISTORY OF FLIGHT On July 26, 2003, at 1028 mountain standard time, a Bell 206L-3, N6184D (fire call sign Helicopter 356), crashed near Whiteriver, Arizona. The Bureau of Indian Affairs (BIA), Fort Apache Indian Reservation, operated the helicopter under the provisions of 14 CFR Part 91. The helicopter was destroyed. The commercial pilot and one passenger were fatally injured; two passengers sustained serious injuries. One person on the ground was not injured. The public-use flight departed the Whiteriver Airport (E24), at 1000, en route to the Wilderness Fire in the vicinity of Aspen Ridge, 12 statute miles from E24. Day visual meteorological conditions prevailed, and a BIA company flight plan had been filed. The first flight of the day to do a reconnaissance work on the Kinishba Fire was performed between 0858 and 0932. The helicopter returned to Whiteriver, and the second flight, the accident flight, departed at 1000. According to a National Weather Service zone forecast for the Northern Arizona area, the weather was forecasted to be partly cloudy in the morning then becoming mostly cloudy, with scattered showers and thunderstorms; light winds, with a 50 percent chance of precipitation. The temperature was forecasted to be from 73 degrees to 80 degrees Fahrenheit. Weather information obtained from the fire lookout reported the weather as 73 degrees Fahrenheit with southwesterly winds from 2-4 miles per hour. The density altitude was calculated to be 11,968 feet. The purpose of the flight was to insert a 3-person helicopter initial attack (helitack) crew to conduct an initial attack for a wildland fire along Aspen Ridge. WITNESS STATEMENTS A reconnaissance flight was the first flight of the day for the accident helicopter. Passengers on board the flight stated that the first flight was at 0830. When the pilot first started the helicopter, the main rotor blades made a "few revolutions," then stopped. After about 2-3 minutes, the pilot was able to start the helicopter. One passenger reported that during the flight, the pilot conducted turns, as well as low-level flight observations with no discrepancies noted. The passenger also reported that the flight was about an hour in length. Another pilot departing E24 recalled hearing "pull up" three times over the radio, followed moments later by "dispatch, dispatch, dispatch, 356 is down, 356 is down." He immediately returned to E24, had the long line and bambi bucket removed, and boarded a helicopter manager along with a paramedic and departed for the accident site. The pilot recalled observing the accident helicopter abort one start earlier that morning. He further stated that on the second start the helicopter "just seemed kind of slow or sluggish to spool up and complete its start." He attributed this to the "warm start" followed by a "slightly weaker battery." Helicopter Manager (HEMG - on board accident helicopter - survivor) The National Transportation Safety Board investigator-in-charge (IIC) interviewed the helicopter manager. He stated that the first flight of the day was a reconnaissance of the Kinishba Fire. The first startup of the day was unsuccessful. The pilot was able to start the helicopter on the second try and no mechanical difficulties were encountered. The first flight of the day was uneventful. The helicopter manager stated that he received a call from dispatch about a fire "going up Aspen Ridge." He stated that he conducted a safety briefing with the helitack crew prior to getting in the helicopter. He was seated in the front left seat, and the three helitack crewmembers were seated in the passenger cabin; two facing forward, and a third seated behind the pilot on the right side in the aft-facing seat. The 3-person helitack crew consisted of a squad boss, and two helitack crewmembers. He also indicated that the pilot was flying with the pilot's door off; however, the other doors remained on. Once airborne they saw smoke from the wildland fire and flew towards it. He stated that the pilot made two passes over the fire. During the two passes they noticed a meadow, and another clearing closer to the fire that they could utilize to make a couple of drops. The plan was to off-load two helitack crewmembers at the meadow, take the third crewman to the landing zone (LZ) with the tools, and then come back to the meadow for the others, ultimately dropping them off at the LZ. The witness stated that when they landed at the LZ with the one helitack crewman and the tools, he heard a "knocking" noise. The pilot mentioned mast bumping, but said everything was okay. When they took off from the LZ, the witness noticed that the torque gauge was at 100 percent and the helicopter was "hard to get off the ground." They landed at the meadow with no problems. No problems were noted with the takeoff from the meadow. However, the witness stated that the climb out was slow. He did not have a chance to look at the torque gauge on this takeoff because he had radioed dispatch to check in. On the flight to the LZ, the witness stated that the helicopter was flying slowly, about 20 feet above the tree line. For unknown reasons, the pilot flew past the LZ, and continued up the drainage area. The witness noted that the torque gauge read 100 percent. Simultaneously the torque reading went from 100 to 105 then to 110 percent as the pilot started to make a right turn. He asked the pilot if the tail rotor was going to stall, but received no response. At that point, he noted the fuel gauge read 200 pounds and the airspeed gauge read zero. The witness stated that as the pilot was beginning the right turn he could see him "fighting with the [flight] controls." He reported that the pilot was moving the collective, cyclic, and "his feet." The witness radioed dispatch, saying "dispatch" six times before the helicopter started to spin. He remembers the helicopter spinning two times to the right, and the next thing he remembered was trying to breathe. In a subsequent interview, the witness also reported that he believed that while they flew from the meadow to the LZ they would land "in the direction the wind was coming from." However, the helicopter continued in a northerly direction up the drainage area when he observed the torque gauge fluctuation. He also noted that the forward airspeed was going to zero as the pilot turned to the right to return to the LZ. He stated that the helicopter started to shake, the torque gauge was at 100 percent and remained at 100 percent as the helicopter continued to climb. At that point he asked the pilot "are we going to have a tail rotor stall shortly?" He indicated that the spin was a "flat spin." Ground Witness The Safety Board IIC interviewed a ground witness to the accident. The helitack crewman had been dropped off at the road LZ, 100 yards west of the accident site. He stated that there were five people in the helicopter when they departed E24. No problems were noted with the flight to Aspen Ridge. They landed at a meadow, and two of the helitack crewmembers exited the helicopter. The helicopter then flew up the drainage area to the LZ, where the witness exited and off-loaded fire packs and tools. He stated that the initial landing was on the front side of a small hump in the road. Prior to his exiting, the pilot moved the helicopter back to a flatter area. When the pilot repositioned the helicopter, the witness heard a knocking noise. The witness stated that the pilot took off again for the meadow. He reported that when the helicopter came back to the LZ, it was about 10-20 feet above the tree line. He estimated that the trees were about 100-feet tall. He also stated that the helicopter was flying slowly. The witness stated that he was getting ready to marshal the flight in when the helicopter flew past him, continuing up the drainage area. The witness reported that he did not know why they flew past him. He looked away to do something else, and heard a noise. When he looked up he saw the helicopter spinning to the right and then lost sight with the helicopter but heard what he believed was the helicopter hitting the trees. The ground witness ran to the accident site, and rescued the survivors. During the rescue he extinguished a post-fire in the engine area. In the ground witness' written statement, he indicated that the LZ closer to the fire was "pretty tight to land in." On the initial landing the helicopter slid "a little then we lifted up a little backwards, and then we landed kind [of] like in [an] upward" attitude. The HEMG indicated it was okay for him to exit the helicopter. However, before he exited he heard a noise, like a "loud thumping noise." He off-loaded the tools, daypacks, and power saw. The helicopter lifted off to pick up the other two helitack crew. He saw the helicopter approach to land at the LZ, but it flew past him another 70 to 150 yards. He then heard the helicopter "sound like it was losing power," so he looked in the helicopter's direction and saw it "going in circles [at] tree top level." He then heard it hit trees and went to render assistance. Rescue Crew A flight and paramedic crew were dispatched to the accident site and responded with in 5 minutes. According to the pilot, they circled the area for an additional 20 minutes looking for a landing site. He identified one spot, the LZ where the accident helicopter had landed once and was attempting to land at again when the accident occurred, that he deemed "iffy." The pilot stated that he didn't want to take any chances landing there; it had a little slope to it - a clear area, but with a "big mound of dirt" on the north side. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed that the pilot held a commercial rotorcraft-helicopter pilot certificate with an instrument rating. The pilot also held a private airplane pilot certificate with an airplane single land rating. The pilot held a second-class medical certificate issued on April 28, 2003. It had the limitations that the pilot must have available glasses for near vision. At that time, the pilot reported on his medical application as having occasional bouts of hay fever. He also reported that he was currently using Sudafed. On the pilot's medical application he reported a total civilian flight time of 1,300 hours, with 90 hours accrued in the last 6 months. According to the operator's records, the company had hired the pilot in September 1999. He had completed recurrent ground training, flight training, and emergency procedures training on January 28, 2003. The pilot's flight duty log showed a total of 126.7 hours flown since January 2003, with 11.1 hours flown during the month of July 2003. A review of the United States Department of the Interior (DOI) Office of Aircraft Services (OAS) paperwork revealed that the accident pilot had been issued an interagency data card on December 17, 2002. The card showed an expiration date of December 31, 2003. On the pilot's most recent application for OAS's interagency data card (2003 fire season), the pilot reported his total time as 2,815 hours (military and civilian), with 2,765 hours accrued as PIC in turbine powered helicopters, and 185 hours accrued in the last 12 months. The pilot also reported a total time of 805 hours in Bell 206 series aircraft with 185 hours in the last 12 months, 48 hours in the last 60 days, and 26 hours in the last 30 days. He also recorded 590 total hours as PIC while flying in mountainous terrain. The operator reported that the pilot flew up to Whiteriver the morning of the accident. The pilot would have had to report at 0700. The flight is about 50 minutes from Phoenix to Whiteriver. The pilot would have had to leave no later than 0545 that morning. AIRCRAFT INFORMATION The helicopter was a Bell Helicopter 206L-3, serial number 51253. A review of the helicopter's Daily Aircraft Maintenance Logs on July 25, 2003, a total airframe time of 3,815.0 hours had been carried forward from the previous log. Total flight hours recorded on July 23, 24, and 25 were 9.5 hours; with a Hobbs stop time of 549.4. Investigators estimated that the total airframe time, at the time of the accident was 3,825.9 hours. The last 500-hour inspection had been completed on April 5, 2003. The last annual/100-hour inspection had been completed on June 5, 2003. The Hobbs hour meter read 550.8 at the accident scene. The helicopter was equipped with a Rolls-Royce (Allison) engine 250 C30P, serial number CAE-897517. The Daily Aircraft Maintenance Logs for July 23, 24, and 25th recorded a total engine time of 2,079.5 hours carried forward from the previous log. Investigators estimated the total engine time at the time of the accident was 2,109.0 hours. Fueling records from the Airwest Helicopters fuel and truck log revealed that on July 26, the helicopter had been refueled with the addition of 19 gallons, with an estimated total of 200 pounds on board at the time of the accident. According to the operator's Daily Aircraft Maintenance Logs on July 16, 2003, at a Hobbs time of 518.3 hours, and aircraft total time of 3,793.4 hours, a 50-hour lube was conducted. There were no defects found and the helicopter was returned to service. The remainder of the Daily Aircraft Maintenance Logs dated from July 17 until the July 25 showed no discrepancies. There was no log entry for the date of the accident. There were no unresolved maintenance discrepancies against the helicopter prior to departure on the date of the accident. According to Bell Helicopter, the accident helicopter was originally certified in 1981 and shipped out of the factory with a shoulder harness restraint system (lap belt, shoulder harness, and inertial reel) for each crew and passenger seat location. This was a required item for continued airworthiness operation unless FAA Form 337 Major Repair and Alteration had been completed. At the time of the accident, there was no shoulder harness restraint system for the rear-seated passengers. According to the operator, they had removed the shoulder harness restraint system. FAA Form 337 was not located in the paperwork obtained from the operator, nor was it on file with the FAA. WRECKAGE AND IMPACT INFORMATION The accident site was located on a logging road in a heavily forested area indicative of northern Arizona terrain. The primary wreckage was at 33 degrees 53.148 minutes north latitude and 109 degrees 40.486 minutes west longitude, with an elevation of 9,232-feet mean sea level (msl). The density altitude was calculated to be 11,968 feet. The helicopter was given the call sign of H356 by Whiteriver dispatch. The helicopter came to rest at the base of a Douglas fir tree lying on its left side. The tree was about 100-feet tall. A 22-foot section (top of the tree) came to rest in front and next to the nose of the helicopter. A 4-foot section of cut tree came to rest with the horizontal stabilizer. The nose of the helicopter was on a magnetic heading of 180 degrees. The debris path was located to the south of the accident site, with the farthest piece found about 50 yards from the main wreckage. The main wreckage consisted of the fuselage, tail boom, doors, transmission, and both main rotor blades. The helicopter was configured for the pilot to fly with the door off. The other doors had separated from the fuselage, but were found in the main wreckage area. The fuselage at the rear seat area was bent nearly 90 degrees along the longitudinal axis. The upper deck of the transmission separated from the helicopter, and was located adjacent to the main wreckage. The upper deck remained attached to the transmission, main rotor mast, main rotor hub, and one main rotor blade. The inboard portion of the main rotor blade had puncture holes in the blade and showed evidence of blue paint transfer on the upper side. The other blade separated approximately 4 feet from the hub. The blade was lying next to the main wreckage. The tail boom separated from the helicopter in two portions. The portion that houses the horizontal stabilizer
The pilot's failure to maintain a minimum translational lift airspeed while maneuvering in high density altitude conditions at near maximum required torque and above the in ground effect hover altitude, that resulted in a loss of tail rotor effectiveness and a loss of control. The pilot's inadequate in flight planning in his failure to note and account for the power requirements necessary to conduct takeoffs and the slow maneuvering flight at the accident site were also causal.
Source: NTSB Aviation Accident Database
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