ILIAMNA, AK, USA
N756HG
Cessna U206G
The airplane impacted level terrain, covered by smooth, wind-blown, snow, in a left bank of 26 degrees or greater. The leading edge of the first impact crater was angled 15 degrees below the horizon. The area surrounding the wreckage for about one mile was featureless, snow-covered, tundra. Beyond one mile, were rising hills with areas of exposed vegetation. Visible and infrared satellite images displayed a band of bright cloud tops and thick clouds, which traversed the flight path of the accident airplane between the departure airport, 27 miles to the east, and the accident site. Similar reflective images existed over a weather reporting station with visibility of one mile in light snow and mist, and overcast ceilings of 1,100 feet. The airplane's heading at the time of impact was in the direction of the departure airport. The GPS receiver was providing navigation information to the original destination at the time of impact. The airplane was equipped with basic flight instruments, and the pilot was required by the company to demonstrate his ability to control the airplane by reference to those instruments. No evidence of any preimpact mechanical anomaly was discovered with the airplane.
HISTORY OF FLIGHT On February 5, 2000, about 1600 Alaska standard time, a wheel equipped Cessna U206G airplane, N756HG, was destroyed when it collided with terrain, at 59 degrees, 44.17 minutes north latitude, 155 degrees, 56.23 minutes west longitude, approximately 27 miles west of Iliamna, Alaska. The commercial pilot and the five passengers on board were fatally injured. The flight was operated by Iliamna Air Taxi, Inc., of Iliamna, under 14 CFR, Part 135, as an on-demand air taxi flight. The flight departed from Iliamna at 1531 for Koliganek, Alaska. Visual meteorological conditions prevailed at both the origin and destination at the time of the accident, and a VFR flight plan was in effect. The flight was considered overdue by the company at 1755. A search was commenced by the company at 1815, and by the Alaska National Guard at 1835. Sunset in the area was about 1800. No emergency locator transmitter signal was received. The airplane was located at 1317 on February 6, in an area of level terrain, covered by about four feet of smooth, wind blown, snow. The terrain within about one mile of the wreckage site was without vegetation and featureless. Beyond one mile were rising hills, with areas of exposed vegetation. INJURIES TO PERSONS All six persons on board the airplane were fatally injured. DAMAGE TO AIRCRAFT The airplane was destroyed by impact forces. PERSONNEL INFORMATION The pilot held a U.S. commercial pilot certificate issued on July 19, 1988. His most recent U.S. second-class medical certificate was issued on April 9, 1999, with the requirement for corrective lenses. He held an airframe and powerplant mechanic certificate issued on March 31, 1987. The pilot was hired by Iliamna Air Taxi, Inc., on April 29, 1998, and worked as both a pilot and mechanic. He lived in Iliamna. He completed initial training, and was assigned to fly the Cessna 207, on June 30, 1998. On December 6, 1999, the pilot completed pilot-in-command checks in the Cessna 206. The pilot had about 50 hours experience in the Cessna 206 at the time of the accident. On each of the pilot's 14 CFR 135.293, and 135.299 Airman Competency / Proficiency Checks, it was noted that the pilot demonstrated "Basic Instrument Competency." In addition, each company Certificate of Flight Training included the following items: "(3) Flight under simulated instrument conditions," and "(8) Flight under simulated IFR conditions using each kind of navigational and approach facility used in normal operation." Flight and Duty Time On the day of the accident, the pilot's estimated total experience was 2,990 flight hours. In the 24 hours prior to the accident, the pilot had flown 5 hours. He completed his flights about 1100 on the day prior to the accident, and went home from work about 1700. He was off duty for 15 hours prior to reporting to work the morning of the accident. The pilot had flown 10.7 hours in the previous 7 days, and 54 hours in the previous 30 days. The pilot's normal workday during the winter months was from 0830 to 1700. He was also employed as a mechanic by the operator, and when not assigned flight duties, was assigned maintenance work. The pilot was described as physically active, and did not use tobacco or alcohol products. He was a salaried employee, not paid on the basis of completion of flights. AIRCRAFT INFORMATION The airplane was manufactured in 1978. It was equipped with a Teledyne Continental IO-520 engine, an external baggage pod mounted under the fuselage, and a Robertson Short Takeoff and Landing (STOL) kit. The airplane was configured to carry one pilot and five passengers at the time of the accident. The airplane was maintained on a 100-hour/annual inspection schedule. 88 hours had elapsed since the most recent 100 hour / annual inspection on June 23, 1999. A review of maintenance records revealed no preexisting anomalies at the time of the accident. The allowable maximum weight of the airplane was 3,600 pounds. The NTSB investigator-in-charge (IIC) estimated the total gross weight at the time of the accident to be 3,500 pounds. Required Equipment All equipment required by 14 CFR Part 91.205, 207, 209, and 135.149, 159, and 161, was installed on the accident airplane. The company was authorized to operate the airplane in day and night VFR conditions. 14 CFR Part 135.159, Equipment Requirements: Carrying Passengers Under VFR At Night, states, in part: "No person may operate an aircraft carrying passengers under VFR at night...unless it is equipped with- (a) A gyroscopic rate-of-turn indicator... (b) A slip skid indicator (c) A gyroscopic bank-and-pitch indicator. (d) A gyroscopic direction indicator..." METEOROLOGICAL INFORMATION The nearest official weather reporting station to the accident site is located at the Iliamna Airport. The terminal forecast for the Iliamna Airport called for 1,500 feet scattered, 3,500 feet overcast, and six miles visibility, with temporary conditions of three miles visibility in light rain and snow showers, and 1,500 feet overcast ceilings The weather observation at the Iliamna airport, at 1553, was ceiling 3,200 feet overcast, 10 miles visibility, temperature 38, dew point 32, winds 140 degrees at seven knots. The weather observation at the Iliamna airport, at 1653, was 3,400 feet overcast, 10 miles visibility, winds 180 degrees at five knots. The Area Forecast for the Bristol Bay area, valid until 0100 Alaska standard time, the evening of the accident was, in part: "scattered 1,500 feet, broken 4,500 feet, broken 8,000 feet. Occasional broken to overcast 1,500 feet, four miles visibility in light snow showers and light rain showers. Isolated ceilings below 1,000 feet, and visibility below three miles." An NTSB senior meteorologist received visible and infrared satellite data from the GOES-10 (Geostationary Operational Environmental Satellite-10) valid at 1545, and 1600, for the accident area. These visible and infrared images showed a band of bright cloud tops, and high levels of reflected solar energy (thick clouds), which extended north-northwestward from Kodiak Island, and traversed the flight path of the accident airplane between Iliamna and the accident site. At the same time as these observations, similar energy reflective images existed for the area of Dillingham, Alaska. Dillingham is approximately 96 miles west-southwest of the accident site. At 1552, the weather observation at Dillingham was: visibility one mile in light snow and mist, ceilings 1,100 feet overcast. The company Operation Specifications, paragraph A010, Aeronautical Weather Data, stated in part: "For VFR operations, the pilots own weather observations, or those of another competent observer may be used when approved sources are not available." Official sunset at the accident location was 1749. The end of evening civil twilight was 1835. AIDS TO NAVIGATION The airplane was equipped with a Bendix-King KLN-89B global position system (GPS) receiver, a Bendix-King KX-155 VHF Omnidirectional Range (VOR) receiver, and an Automatic Direction Finder (ADF) receiver. The KLN-89 GPS was tested at Bendix-King's facility in Olathe, Kansas, under the supervision of an FAA avionics inspector from the Kansas City, Missouri, Flight Standards District Office (FSDO). This inspection and data extraction revealed that the GPS was selected to navigate from the airplane's present position to Koliganek. The present position retained in nonvolatile memory in the KLN-89 is updated every 60 seconds. The present position of the airplane last recorded in nonvolatile memory was 59 degrees 44.17 minutes north latitude, 155 degrees 56.34 minutes west longitude. This position is less than 1/2 mile on a bearing of 245 degrees magnetic from the accident site. It could not be determined how many seconds (from one to 60) prior to the impact that this last position was recorded. The VOR frequency selected was 112.8 MHz (King Salmon, Alaska), and the standby frequency was 116.4 MHz (Dillingham). COMMUNICATIONS The airplane was equipped with a Bendix-King KX-155 communication radio. The radio was tested at the manufacturer's facility under the supervision of an FAA avionics inspector from the FAA Kansas City FSDO. The communication frequency displayed for use in the radio at the time of the accident was 125.6 MHz, and the standby frequency was 122.9 MHz. At 1529 the pilot of N756HG contacted Kenai Flight Service Station on the radio and filed a VFR flight plan from Iliamna to Koliganak. At 1530, the pilot of N756HG activated his flight plan At 1754 on February 5, the FAA Kenai AFSS specialist on duty placed a telephone call to the operator. He said they were looking for N756HG, and that he was 25 minutes overdue on his flight plan. The company president responded that the company was beginning to look also, and was about to fly the route. Kenai asked if the company would like to extend the flight plan. The president responded yes, about 30 minutes. The company radio log has the following entries: 6:15 "Tim Left" 6:25 "Called RCC 800 420-7230 re: overdue" 6:35 "10 min past last due time" 6:45 "Army Guard helicopter disp" No radar coverage is available in the area of the accident, or along the proposed route of flight. WRECKAGE AND IMPACT INFORMATION The NTSB IIC, a representative of the FAA, Cessna, and Teledyne Continental Motors, and two Alaska State Troopers, began the on-site investigation about 1100 on February 8. The temperature at the time the NTSB IIC arrived on scene was about 38 degrees Fahrenheit. No snow or ice was adhering to the wreckage. A review of photographs taken by company and National Guard personnel about 1400 on February 6 revealed no snow or frozen precipitation adhering to the airplane or wreckage. The airplane's fuselage and cabin came to rest about the 695 feet msl level of the Stuyahok River drainage. The surface consisted of smooth, soft, snow. A single linear gouge in the snow, measuring 37 feet long, lead up to the first impact crater. This linear gouge was oriented on a heading of 100 degrees magnetic, and contained the left wingtip, a red position light lens, and the left wingtip strobe assembly. No other marks were visible in the snow prior to the leading edge of the first crater. The minimum angle of bank at which the left wingtip can contact a level surface without the left wheel or belly pod making contact is 26 degrees. The debris field was oriented along a main axis of 070 degrees magnetic, and extended in a linear pattern for a distance of 274 feet. The leading edge of the first crater was angled between 10 and 15 degrees below the horizon. This crater measured 12 feet long, 7 feet wide, and 3 feet deep. Debris was distributed 40 feet to the right, and 40 feet to the left of the centerline of the debris path. The propeller separated from the engine, and was located 10 feet to the right of the debris path centerline, 214 feet from the initial impact gouge. All three blades displayed torsional twisting, and forward bending. The engine was partially broken free of its mounts. Oil was smeared in the snow from the location of the propeller, to the location of the main wreckage and engine. No evidence of streaming oil was seen on the inside or outside of the fuselage or engine cowl. No preaccident fuel system anomalies were noted. Both wing fuel tanks remained intact, and both contained about 20 gallons of a blue fluid, which smelled and felt like gasoline. The airplane was airlifted from the accident site, to a hangar in King Salmon, Alaska, on February 9 and 10, for detailed inspection. Continuity of flight controls was established from all flight control surfaces to the cockpit. No preimpact mechanical anomalies were found. MEDICAL AND PATHOLOGICAL INFORMATION A postmortem examination was performed on the pilot by the Alaska State Medical Examiner, 5700 East Tudor Avenue, Anchorage, Alaska, on February 7, 2000. The cause of death was noted to be blunt impact injuries. Toxicological samples were tested at the FAA Civil Aeromedical Institute (CAMI), Oklahoma City, Oklahoma, on March 20, 2000. A glucose level of 165 (mg/dl) was detected in the pilot's urine. According to the CAMI report, urine glucose levels above 100 mg/dl are considered abnormal. Glucose may be produced as a physiologic stress response, regardless of consciousness. The autopsy performed on the pilot indicated that he had extensive head injuries, and remained alive for a short time after the impact. A review of medical records from physicians who had previously treated the pilot revealed no evidence of preaccident impairing anomalies. SURVIVAL ASPECTS Emergency Locator Transmitter (ELT) The ELT did not radiate a signal. The Alaska State Troopers who first arrived at the accident site confirmed the ELT was selected to the "ARM" position. The ELT had broken free from the right side of the airplane and was found loose in the aft baggage area. The ELT remained secured to the factory provided mounting tray by two quick release straps. The four rivets, which attached the mounting tray, had pulled out of the aircraft structure. The company had removed and reinstalled the ELT assembly during a recent rebuild of the airplane. The new installation of the ELT consisted of aluminum angles attached to primary aircraft structure, to which the mount tray was riveted. According to the mechanic who reinstalled the ELT in the airplane, the ELT mounting tray was already riveted to the angle bracket by the four rivets which pulled out. After the airplane was rebuilt from a previous accident, he riveted the angle bracket to the new angles and primary structure. The mechanic and owner stated that they did not know who installed the four failed rivets. The ACK Technologies, Inc., Model E-01 Installation Manual, specifies that the mounting tray be installed using 6-32 screws, flat washers, and nylock nuts. It also states that a doubler plate may be required, and that the tray be mounted to load carrying structure, "not aircraft skin." It states that deflection of not more than 0.1 inch is allowed when a load of 100 pounds is applied to the mounting tray. Examination of the ELT mounting bracket by NTSB materials laboratory technicians on May 9, revealed all four failed rivets exhibited bucking process expansion to only 180 degrees of their respective circumferences. It was also noted that the airframe structure to which this bracket was mounted did deform slightly prior to the four rivets pulling through. No prexisting cracks were noted. The coaxial ELT antenna cable was severed about 18 inches from the ELT, and the remote cockpit control cable was pulled free of the ELT housing. The ELT was sent to the manufacturer for disassembly and testing under supervision of the FAA. Cabin Survivability The cabin did not collapse, and the internal volume of the cabin was not compromised. Both the forward left door, and the right cargo door came open. The cargo net located behind the rear seat passengers was in place. The airplane's survival kit was contained in a rectangular metal can and was normally restrained by a cargo net. The net was torn, and the can was found loose in the cabin. The front seat occupants were both found restrained in their respective seats by seatbelts and shoulder harnesses. The passenger seat restraints appeared weathered and worn. One of the passenger restraints failed at the webbing. A second failed at the stitching. Ultimate load testing of the passenger seatbelts performed under the direction of NTSB materials laboratory technicians, revealed the seatbelt webbing sustained loads in excess of the required 1,500 pounds minimum. See attachment for additional information. The passenger seated in the left-center seat was ejected, and found under the left wing. Search and Rescue At 1850, the airplane was declared overdue by the FAA. At 1905, Information Request (INREQ) procedures were commenced, looking for the airplane. An Alert Notice (ALNOT) was issued for the overdue airplane at
The pilot's attempted flight into adverse weather, and his failure to maintain altitude/clearance above the snow-covered tundra. Factors associated with the accident were snow, rain, and whiteout conditions.
Source: NTSB Aviation Accident Database
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