Easton, WA, USA
N7531D
Robinson R44 II
The helicopter was departing from a clear cut area in forested mountainous terrain at an elevation of 4,961 feet. A witness observed the helicopter lift off vertically, oriented in a southerly direction, to an altitude of about 40 feet before turning 90 degrees to the left and proceeding down the hillside to the east. The helicopter then began to sway back and forth after traveling about 100 to 150 feet, then it impacted the ground in a nose low, left bank attitude. The witness stated that the wind was switching around during the morning, and that it was blowing down slope toward the east at the time of the accident. The closest weather reporting facility, which was located 8 miles west of the accident site, reported winds gusting out of the west to 16 knots. No evidence of any preimpact anomalies were found during the post accident examination that would have precluded normal operation. During the accident flight the helicopter was being operated 77 pounds over the maximum gross weight for an Out of Ground Effect hover for the existing conditions. The helicopter was being operated in a high density altitude environment, which was computed to be 6,841 feet mean sea level.
HISTORY OF FLIGHT On August 2, 2007, about 1420 Pacific daylight time, a Robinson R44 II helicopter, N7531D, was destroyed after impacting mountainous terrain during takeoff about five miles southwest of Easton, Washington. The commercial pilot and three passengers were killed. The helicopter was registered to Comprador Helicopters LLC, of Bellevue, Washington, and operated by Classic Helicopter Corp., of Seattle, Washington. Visual meteorological conditions prevailed at the time of the accident for the cross-country charter flight, which was being operated in accordance with 14 Code of Federal Regulations Part 135. A flight plan was not filed. The flight was originating at the time of the accident, and its destination was Smith Island, Washington. In an interview with the NTSB investigator-in-charge (IIC), the helicopter operator reported that the purpose of the three-leg cross-country flight was to transport one local businessman and two South Korean businessmen to logging sites to inspect lumber. The first leg of the flight was to be from Boeing Field/King Country International Airport (BFI), Seattle, Washington, to the Barbeu Mill Corporation logging site, located about 5 nautical miles southwest of Easton. The second leg of the flight would be from the Barbeu Mill to Smith Island, located about 130 nautical miles northwest of the accident site, with the third leg being the return flight to BFI. The operator further reported that the flight departed BFI about 1300. In a written statement provided to the IIC by the owner of the logging company, at 1335 he reported observing the helicopter circle the timbered property and land on a logging road about 1,000 feet from his position. The witness reported seeing three people exit the helicopter, but not the pilot, who he reported remained in her seat. The witness stated that after visiting with the passengers for about 30 minutes they returned and boarded the helicopter. The operator reported that at 1408 the pilot called their base of operations at BFI and stated that the passengers were returning to the helicopter, and that they were preparing to depart for Smith Island with 39 gallons of fuel on board. The witness reported that about 5 minutes after the passengers had returned to the helicopter he heard the engine start, then observed the helicopter ascend "straight up" about 40 feet facing in his direction (south), before turning 90 degrees to the left (east) flying toward the valley it had originally flown up. The witness stated that after flying approximately 100 to 150 feet, "...the helicopter began to wobble/sway, and I noticed a difference in sound coming from the helicopter." The witness revealed that he observed the helicopter fly about another 100 to 150 feet "wobbling" before seeing it descend and impacting the ground on its left side, with the tail higher than the cockpit. The witness stated that the helicopter was immediately engulfed in flames about 30 feet high, and that the wind at the time was blowing "...down the hill." As a result of the post crash fire, which encompassed several hundred acres surrounding the accident site, the on-site examination of the wreckage was postponed until local fire control personnel deemed the region safe, which occurred on August 4, 2007. PERSONNEL INFORMATION The pilot, age 41, held a commercial pilot certificate with a rotorcraft-helicopter rating issued on July 11, 2002. The pilot was issued a certified flight instructor certificate with a rotorcraft-helicopter rating on February 27, 2004. A review of the pilot's personal logbook revealed a total time in helicopters of 2,122 hours, 1,492 hours of instruction given in helicopters, 160 hours in the last 90 days, 24 hours in make and model, and 55 hours in the preceding 30 days, with 8 hours in make and model. The pilot received a second-class airman medical certificate on March 13, 2007, without limitations. The pilot's most recent biennial flight review was completed on January 4, 2007. AIRCRAFT INFORMATION The 2004-model R44 II helicopter, serial number 10412, was powered by a Lycoming IO-540-AE1A5 engine. The helicopter underwent its most recent inspection in accordance with the Classic Helicopter Corp. (CHC) Robinson R-44 50 hour inspection checklist, on July 6, 2007, at a total engine and airframe total time of 487.6 hours. The helicopter's most recent 100 hour/annual inspection, in accordance with the Robinson R-44 maintenance manual, sections 2.210 and 2.410, also using the CHC Lycoming engine 100 hour/annual inspection checklist, was conducted on June 1, 2007, at a total airframe and engine time of 435.6 hours. A calculated gross takeoff weight provided by the manufacturer's representative was based on the following weights: Empty weight: 1588 pounds Pilot (front right seat): 120 pounds Front left seat passenger: 190 pounds Rear left seat passenger: 160 pounds Rear right sear passenger: 150 pounds Main fuel tank: 150 pounds Auxiliary fuel tank: 84 pounds Ballast: 25 pounds The calculated gross weight at the time of the accident was 2,467 pounds, with a Center of Gravity (CG) of 95.3 inches. This placed the helicopter within the weight and balance envelope. Based on FAA approved hover performance capability performance charts for the R44 II, at a gross takeoff weight of 2,467 pounds and an outside air temperature of 73 degrees Fahrenheit, the helicopter would have been able to hover In Ground Effect up to an altitude of 7,700 feet mean sea level (msl). Out of Ground Effect and at its gross takeoff weight of 2,467 pounds, the helicopter would have been able to hover at a maximum altitude of 3,700 feet msl. Calculations also indicate that the helicopter would have been able to hover Out of Ground Effect at the accident altitude of 4,906 feet msl at a maximum gross weight of 2,390 pounds, 77 pounds less than the helicopter's gross takeoff weight at the time of the accident. METEOROLOGICAL INFORMATION The closest weather reporting facility to the accident site, located about 8 nautical miles northwest of where the wreckage came to rest, was the Stampede Pass Automatic (SMP) Automated Surface Observation Station (ASOS). At 1356, the SMP automated weather reporting facility reported no wind direction give, velocity 6 knots, with gusts to 16 knots, sky clear, temperature 73 degrees F, dew point 43 degrees F, and an altimeter setting of 30.10 inches of Mercury. At 1456, the SMP automated weather reporting facility reported wind from 250 degrees at 8 knots, gusts to 16 knots, sky clear, temperature 73 degrees F, dew point 43 degrees F, and an altimeter setting of 30.10 inches of Mercury. Density altitude at the time of the accident was calculated to be 6,841 feet. WRECKAGE AND IMPACT INFORMATION On August 4, 2007, documentation of the accident site was conducted. A survey of the accident site revealed that the helicopter impacted down sloping, clear-cut terrain, estimated at 30 degrees, on a magnetic heading of 078 degrees. The helicopter came to rest inverted on a magnetic heading of 141 degrees, at an elevation of 4,907 feet msl. The measured distance from the takeoff point, elevation 4,961 feet msl, to the main wreckage was 370 feet. The debris path was oriented along a magnetic heading of about 101 degrees and consisted of one tail rotor blade 17 inches in length with its outboard tip attached, located 140 feet upslope from the main wreckage. A second tail rotor blade, 12 inches in length with its outboard tip missing, was located 48 feet upslope from the main wreckage and 92 feet down slope from the first tail rotor blade; the blade tip was never accounted for, either during the onsite or post accident examinations. Additionally, the tail rotor gear box, tail rotor hub, a section of the tail rotor drive shaft, and the empennage and tailcone were found 29 feet northeast of the main wreckage. The remaining section of the tail rotor drive shaft was located 58 feet north of the main wreckage. The cabin area was completely destroyed by a post impact fire, which consumed the forward portion of the helicopter, including most of the flight instruments. The flight control system was destroyed by fire, with much of the control system unidentifiable. No evidence of pre-impact failures of the flight control system was noted. The helicopter's airframe was destroyed by fire, with the horizontal and vertical firewalls, upper and lower steel tube frames the only remaining components, which could be identified. Several of the members were bent and fractured, and the vertical firewall was damaged on the left side. Portions of the aft end of the tailcone and empennage were identifiable. On August 4, 2007, the helicopter was recovered from the accident site to a secured storage facility for further examination. MEDICAL AND PATHOLOGICAL INFORMATION Toxicological testing on the pilot was performed by the FAA Civil Aeromedical Institute's (CAMI) Forensic Toxicology and Accident Research Center at Oklahoma City, Oklahoma. The toxicological tests were negative for alcohol and drugs. An autopsy of the pilot was conducted on August 8, 2007, at the Central Washington Hospital Morgue, Wenatchee, Washington. The cause of death was listed as "asphyxia by inhalation of products of combustion and thermal injury." TESTS AND RESEARCH NTSB Materials Laboratory examinations: Four (4) pieces of tail rotor blade and light bulbs from a section of the helicopter's instrument panel were sent to the NTSB Materials Laboratory in Washington, D.C. for examination. As a result of the examination of the light bulbs, a Senior Materials Engineer reported that eight (8) light bulb filaments were disassembled from the helicopter's instrument panel and examined for evidence of hot stretching. All bulb filaments were found to be intact from post to post, with no signs of stretching or other deformation that would indicate that any of the lights were on at the time of impact. The engineer reported that the examination of the tail rotor blades (4 pieces), labeled Blade A accompanied by Piece 1, and Blade B accompanied by Piece 2, revealed that each of the four pieces was fractured at one or both ends, and that mating fracture features were observed at the inboard end of Blade B and the outboard end of Piece 2. The examination further revealed that fracture surfaces on the outboard end of Piece 1 were obliterated by heat damage, but the overall fracture orientation of Piece 1 was consistent with mating with the fracture at the inboard end of Blade A. Additionally, it was reported that skin fracture features at the inboard end of Blade A were gray and on slant planes consistent with overstress fracture. Further, Blade B exhibited skin fractures that were gray and on slant planes consistent with overstress fracture. On August 21, 2007, under the supervision of the IIC, an examination of the engine and airframe was conducted at the facilities of a local salvage company. The results of the examinations failed to reveal any anomalies, which would have precluded normal operation of the helicopter.
The pilot's improper planning/decision in attempting a downwind takeoff under high density altitude conditions that resulted in a loss of control and impact with terrain. Contributing to the accident were the helicopter's gross weight in excess of the maximum hover out of ground effect limit, a high density altitude, and the gusty tailwind.
Source: NTSB Aviation Accident Database
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