AIRCRAFT 1 PRELIMINARY REPORT

HISTORY OF FLIGHT On June 19, 2000, about 1815 Alaska daylight time, a wheel/ski equipped Cessna 185E airplane, N1589F, was destroyed when it broke-up in flight over a remote area of the Denali National Park and Preserve, about 52 miles west of Talkeetna, Alaska. The airplane was being operated as a visual flight rules (VFR) U.S. Government flight by the U.S. Department of Interior, National Parks Service (NPS), Talkeetna, Alaska, when the accident occurred. The airplane, provided by Hudson Air Service Inc., Talkeetna, was utilized on an on-demand Title 14, CFR Part 135 flight. The airline transport certificated pilot and the three passengers received fatal injuries. A VFR flight plan was filed. The flight originated at the Talkeetna airport at 1710. The flight was conducted to transport a National Park Service ranger, and two volunteer rangers, to the Denali National Park base camp, located at 7,200 feet msl on the southeast fork of the Kahiltna glacier, about 48 miles northwest of Talkeetna. The three rangers were to begin mountain patrol operations on Mt. McKinley. The director of operations for the operator reported that variable weather conditions near the National Park Service's base camp made landing at the base camp problematic throughout the day of the accident. The accident pilot had flown a company Cessna 172 over the areas of the Ruth and Tokositna glaciers between about 0950 and 1050. When he departed Talkeetna at 0947 in the Cessna 172, a flight service station specialist at the Federal Aviation Administration (FAA), Talkeetna Flight Service Station (FSS), opened a VFR flight plan for the flight, and gave the pilot an advisory that stated, in part: "AIRMET for mountain obscuration and turbulence are current for Cook Inlet, and Susitna Valley..." The director of operations reported that before departing on the accident flight, the pilot commented he would wait to see if conditions improved during the day near the Kahiltna base camp before canceling the flight for the National Park Service. The pilot filed a VFR flight plan with the Talkeetna FSS, and departed Talkeetna at 1710, headed for the Kahiltna base camp in the accident airplane. When the pilot filed his flight plan, the FSS specialist included an advisory that stated, in part: "...still an AIRMET for low altitude turbulence, let me know if you need details." The National Park Ranger on board, contacted the Talkeetna Ranger Station by a hand-held radio about 1710, and reported that he would be unable to do any flight following during the flight, but he would contact the ranger station when the airplane landed at the Kahiltna base camp. After departure, at 1714, the accident airplane pilot talked via radio to another airplane pilot (N70176) about conditions in the area of the Kahiltna base camp. The radio conversation was recorded at the Talkeetna FSS. The accident pilot asked: "...you haven't heard anybody talking about getting up to the base camp have you?" The pilot of N70176 replied: "No, I was in on the Ruth (glacier) and that is open at the moment, but looking from Moose's Tooth (peak) over south Hunter (pass), looked like it was closed, and I haven't heard anything about the Kahiltna." About 1757, the ranger on board the accident airplane contacted the Talkeetna ranger station by a hand-held radio and stated the flight was returning to Talkeetna from the area of the Kahiltna icefall. The pilot of a McKinley Air Service airplane landed at the Kahiltna base camp in the afternoon of the accident. The pilot reported that due to a dead battery, she did not depart the base camp until about 1800, heading for Talkeetna. As she proceeded southbound, she said the accident airplane pilot contacted her via radio and reported low clouds over the Kahiltna glacier icefall, and said he was returning to Talkeetna. The McKinley Air pilot also observed low weather conditions over the icefall and headed back to the base camp. The accident airplane pilot again called the McKinley Air pilot and reported that the weather conditions had closed in over the Big Bend of the Kahiltna glacier (lower on the mountain, south of the base camp). He also reported that the Pica glacier (east of the Kahiltna glacier) area was closed, but he could see light on the Lacuna glacier (west of the Kahiltna glacier), and was going to head toward that location. The McKinley Air pilot responded by saying that attempting to proceed to the Kahiltna base camp was not an option. This was the last radio transmission received from either the accident airplane pilot or passengers. The McKinley Air pilot then landed at the base camp where the airplane and passengers remained overnight due to fog and snow showers. The McKinley Air pilot said that the wind was very light, with no turbulence. The accident airplane did not arrive in Talkeetna, and was reported overdue at 1955. The wreckage was located on June 20, 2000, at 1617, by search aircraft. An Alaska State Trooper helicopter landed below the accident site and verified the identity of the wreckage. The accident occurred during the hours of daylight at latitude 62 degrees, 42.489 minutes north, and longitude 151 degrees, 45.385 minutes west. PERSONNEL INFORMATION The pilot was the chief pilot for the operator. He held an airline transport pilot certificate with a multiengine rating. He also held a commercial pilot certificate with airplane single-engine land, and single engine sea ratings. The most recent second-class medical certificate was issued to the pilot on April 18, 2000, and contained no limitations. The aeronautical experience listed on page 3 of this report was obtained from a review of information from the operator. According to the operator's records, the pilot's total aeronautical experience consisted of about 9,095 hours, of which about 2,000 were accrued in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the pilot flew a total of 142 and 108 hours, respectively. The pilot's normal scheduled duty day was from 0800 to 2200. In the three days prior to the accident, the pilot was off duty on June 17. On June 18, he flew 6.25 hours. On the accident date of June 19, he flew 3.0 hours. The pilot was hired by the operator on March 13, 1995. His most recent company recurrent training was completed on February 6, 2000. Some of the training topics covered in the operator's training manual include mountain flying, and glacier operations. The pilot's most recent FAA Part 135.293, and Part 135.299, airman competency/proficiency check was conducted on April 18, 2000, in a Cessna 172. The pilot received an interagency pilot evaluation/qualification recurrent check from a Department of the Interior, Office of Aircraft Services inspector, on April 25, 2000, in a Cessna 185. The operator holds an on-demand air taxi certificate. The company's management personnel include the director of operations, the chief pilot, and the director of maintenance. The duties, responsibilities, and authority, listed in the operator's operations manual, for the director of operations, include: Ensure the safe and organized operation of the company; ensure that company aircraft are airworthy; train and instruct company personnel in their specific duties; responsible for the safe operation and oversight of aircraft and company personnel; acts as the representative of the company; may dispatch and cancel flights; and is the final authority for company operations, policies, aircraft, pilots, and ground personnel. The chief pilot duties, responsibilities, and authority, include: Ensure that company pilots operate within the FAA's and company's policies; conduct pilot training and ensure they conduct themselves in a professional manner; ensure that pilot records are current; and may dispatch flights in accordance with the company training program. The director of maintenance duties, responsibilities, and authority, include: Schedule/perform required maintenance and inspections; keep the maintenance records up-to-date, including pilot notification forms and ADs; notify the director of operations of any mechanical irregularities; act as the company maintenance representative between the FAA and the company; remove from, or return company aircraft to service; and may operate company aircraft on the ground. In the Pilot's Responsibilities and Procedures section of the company operations manual, it includes, among others, the requirement that before flight, the pilot-in-command shall ensure the required airworthiness inspections have been made. This can be accomplished by a review of the Pilot's Notification sheet that is maintained for each company airplane. In the operational control section of the company operations manual, it includes the following: "The director of operations will have the responsibility for operational control. If the director of operations is not available, he may delegate this responsibility to the chief pilot, or the director of maintenance. In such a case, the delegated person must be notified of each and every flight that occurs. If, for any reason, the PIC (pilot-in-command) of a flight feels that the flight cannot be conducted or completed, he has the right to turn down, or cancel the flight." AIRCRAFT INFORMATION At the time of the accident, the airplane had accrued a total of 7,130.4 hours. The airplane was maintained on an approved aircraft inspection program (AAIP). The AAIP has four inspection cycles that are scheduled every 50 hours. Each inspection cycle may be completed within 10 hours before, to 10 hours after, the anticipated 50 hour cycle. The completion of all four cycles qualifies as an annual inspection. The latest four cycle inspection was completed on December 3, 1999. Examination of the maintenance records revealed that the most recent inspection cycle was number three, accomplished on May 28, 2000, at an hour reading of 1133. At the accident site, the recording hour meter within the airplane's tachometer was indicating 1204.9, which is 11.9 hours beyond the required inspection time. The engine had accrued a total time of 1,684 hours. The maintenance records note that a major overhaul was accomplished on August 13, 1998, 516.9 hours before the accident. The airplane's wheel/ski assemblies, Fluidyne model C-3600, were installed on the airplane on October 10, 1999. The wheel/ski assemblies utilize a coiled spring/cable and a second safety cable attached to the tip of each ski, and a separate safety cable attached to the trailing end of each ski. The operator reported that during flights to and from the Kahiltna glacier area, no radar coverage is available, and the radar transponder is not utilized. The airplane was equipped for basic instrument flight which, among others, included an attitude indicator, a heading indicator, a rate of turn indicator, and a vertical speed indicator. The airplane was equipped with a Robertson Aircraft Corporation, Short Takeoff and Landing (STOL) modification that was installed under supplemental type certificate (STC) SA1441WE on April 16, 1969. The Robertson STOL STC is currently owned by Sierra Industries Inc., Uvalde, Texas. The Robertson STOL modification on the accident airplane, incorporated a contoured wing leading edge, upper wing surface stall fences, a filler strip between the trailing edge of the wing and the ailerons, and the ability of the ailerons to droop as the flaps are extended. The amount of aileron droop, as the flaps are extended, is as follows: Flaps zero; Ailerons are at zero degrees, plus or minus 2 degrees. Flaps at 10 degrees; Ailerons are at 8 degrees, plus or minus 2 degrees. Flaps at 20 degrees; Ailerons are at 13 degrees, plus or minus 2 degrees. Flaps at 30 degrees; Ailerons are at 15 degrees, plus or minus 2 degrees. Flaps at 40 degrees; Ailerons are at 12.5 degrees, plus or minus 2 degrees. According to Sierra Industries personnel, the Cessna 185 wing design, and the utilization of the Robertson STOL modification incorporating a contoured wing leading edge, does not alter the chordwise or spanwise pressure distribution, nor does it change the wing aerodynamic center. Its sole function is to increase the angle of attack range over which the wing stalls, making the stall characteristic very docile. In addition, the modification does not change the flaps up, or flaps down, lift/drag ratio, control capabilities, or the airplane's handling qualities. According the Cessna Aircraft Company, the following airspeed limitations are listed in the owner's manual: Maximum airspeed (Vne), 210 MPH; Maximum structural cruising speed (Vno), 170 MPH; Maneuvering speed (Va), 138 MPH; Maximum speed, flaps extended (Vfe), 110 MPH. The airframe flight load factors, for flaps up; 3.8 positive to 1.52 negative. The flight load factor for flaps down; 3.5 positive. No negative load factor is listed for flaps down. The manufacturer indicated that the design load factors are 150 percent of the flight load factors, and in all cases, the structure meets or exceeds design loads. METEOROLOGICAL INFORMATION On June 19, 2000, at 1753, an Aviation Routine Weather Report (METAR) from Talkeetna was reporting, in part: Wind, 220 degrees (true) at 13 knots, gusts to 21 knots; visibility, 10 statute miles; clouds and sky condition, 2,500 feet scattered, 4,100 feet broken, 4,900 feet overcast; temperature, 55 degrees F; dew point, 44 degrees F; altimeter, 29.68 inHg; remarks, pressure rapidly rising. At 1553, a METAR from Skwentna, Alaska, located 47 miles south-southeast of the accident site, was reporting, in part: Wind, 170 degrees (true) at 6 knots; visibility, 20 statute miles in light rain; clouds and sky condition, 2,500 feet broken, 6,000 feet broken, 10,000 feet overcast; temperature, 55 degrees F; dew point, 50 degrees F; altimeter, 29.69 inHg. At 1654, a METAR from Chulitna, Alaska, located 54 miles east of the accident site, was reporting, in part: Wind, calm; visibility, 40 statute miles; clouds and sky condition, 6,000 feet broken, 10,000 feet overcast; temperature, 55 degrees F; dew point, 34 degrees F; altimeter, 29.66 inHg; remarks, breaks in the overcast, all quadrants. A National Weather Service forecast for the Denali Park area, issued on June 19 at 1130, stated, in part: "This afternoon, mostly cloudy. Scattered areas of light rain. South winds gusting to 30 mph in channeled areas." A National Park Service ranger at a camp at 14,200 feet on Mt. McKinley reported that between 1700 and 1900, the weather conditions included a visibility of 1/2 mile in light snow, and a 0 to 5 knot wind from the south. The pilot of the airplane at the Kahiltna base camp that talked with the accident pilot, and a National Park Service ranger who was camped about two miles south of the Kahiltna base camp, both reported the weather conditions included low clouds, scattered snow showers, and fog. The owner of the Angle Haven Lodge, located along the Yentna River, 31 miles south of the accident site, reported that about 1800, he and several of his clients were fishing next to the lodge. He saw a large wall of cumulus clouds approaching from the south. The wall of clouds was preceded by high winds. The storm contained extremely heavy rain, the heaviest rain the owner had ever observed. The storm was fast moving, proceeding from the south to the north, toward the base of the Alaska Range. The storm lasted about 1 to 1 1/2 hour. A weather study was conducted by an NTSB senior meteorologist. All times in the study are Alaska daylight time. The weather study noted the National Weather Service's 0305 synoptic report stated, in part: "...an occluded front across the Kuskokwim Delta, the Kuskokwim Valley, northern Cook Inlet and Prince William Sound, will dissipate over the Tanana Valley, lower Yukon Valley, and the Yukon-Kuskokwim Delta on Monday." The 0859 synoptic report stated, in part: "...a cold upper low in the vicinity of King Salmon will continue to drift northeast toward the Cook Inlet today. An air mass across south central and southwest Alaska, is increasingly unstable as cold air aloft phases with maximum afternoon heating. Thundershower activity likely over this broad area." The 1450 synoptic report stated, in part: "...a secondary low is rolling in over the lower Cook Inlet, with an associated frontal system, located about Kenai to Seward at 1400. Winds will slowly turn southwesterly with a low in the western Cook Inlet, with the pressure gradient forcing a more easterly component. The main low center to fill in the vicinity of King Salmon, and will begin drifting to the north. The air mass will remain unstable, with probabilities of precipitation remaining fairly high across most of the forecast area during the next 24 to 36 hours for shower activity. A few thundershowers are possible this evening especially along the elevated heat source along the Alaska Range. Plain old rain in the Prince William Sound." A surface analysis chart, prepared by the National Weather Service Forecast Office at 1600, charted an east-west occluded front extending through the Talkeetna area. A review of selected pilot reports in the Anchorage area, included: At 1107, at 2,000 feet, severe turbulence in the area of Turnagain Arm. At 1110, low level wind shear during the landing approach to runway 6R. At 1208, low level wind shear. At 1519, about 60 miles northwest of Anchorage, remarks, flight visibility is 3 to 5 miles in light rain; occasional light turbulence in the area of the Kahiltna River, otherwise good visual flight rules. At 1618, about 48 miles north-northwest of Anchorage, flight visibility 20 to 25 miles, remarks, visibility occasionally 3 miles in moderate rain showers. Pilot reports in the Mt. McKinley area, included: At 1023, sky condition, 4,000 feet overcast; turbulence, light chop; remarks, light snow on glaciers, freezing level at 6,000 feet, upper peaks obscured. At 1053, sky condition, 5,000 feet overcast; remarks, area above the Ruth glacier is closed, the Tokositna glacier is closed above 5,000 feet, precipitation in canyons. At 1322, remarks, Second Shot Pass, and Kanakula glacier are open, the Kahiltna glacier open to just below base camp, the ceiling at the Pica glacier is 8,500 feet. At 1522, remarks, major snow shower at the icefall, visibility going down quick. At 1614, Talkeetna to Healy, remarks, wind from the south at 45 knots. At 1618, at Windy Pass, sky condition, 5,000 feet overcast; visibility 10 miles; wind, 180 degrees at 40 knots; turbulence, light to moderate. A terminal forecast for the Talkeetna area, issued on June 19, 2000 at 1535, and valid from 1600 to 1600 on June 20, included, in part: Wind 010 degrees at 6 knots; visibility, greater than 6 miles; clouds and sky condition, 3,500 feet scattered, 7,000 feet scattered, 13,000 broken. Temporary conditions from 1600 to June 20 at 1600, light rain showers with broken clouds at 2,500 feet. From 2200 to 0000, wind 180 degrees at 8 knots. An area forecast for the southern half of Alaska, issued on June 19, 2000 at 1530, and valid until 0000, included, in part: Cook Inlet and Susitna Valley, AIRMET for mountain obscuration, Alaska Range obscured in clouds and in precipitation, no change. West side of the Cook Inlet, and the Alaska Range, clouds and sky condition, 2,000 feet broken, 5,000 feet overcast; visibility, 4 miles in light rain and mist. Isolated ceilings below 1,000 feet; visibility, below 3 miles in light rain and mist. Homer south, spreading to Kenai by 1600 and Palmer by 2000, 2,000 feet broken, 3,500 feet overcast, merging layers to 25,000 feet; visibility, 4 miles in light rain. Surface wind from the southeast with gusts to 35 knots. Elsewhere, 5,000 feet scattered, 8,000 feet broken to overcast, tops at 11,000 feet, layers above with tops at 25,000 feet. Isolated areas of 2,000 feet scattered, 5,000 feet broken, 8,000 feet overcast; visibility 5 miles in light rain. In the vicinity of east side of passes or gaps in the terrain, surface wind from the east at 20 knots, with gusts to 35 knots. Outlook, valid June 20, 2000, from 0000 to 1800, in the vicinity of mountains, marginal visual flight rules, occasional instrument rules with ceilings due to moderate rain. Elsewhere, visual flight rules with moderate rain showers. Passes; Lake Clark, Merrill, Rainy, Windy, and Portage, marginal visual flight rules, occasional instrument flight rules with ceilings due to moderate rain. Turbulence; AIRMET for turbulence and low level wind shear, occasional moderate turbulence below 8,000 feet. Palmer south, especially in the vicinity of mountains and Turnagain Arm, low level wind shear and isolated severe turbulence within 2,000 feet above the ground lever, intensifying. Ice and freezing lever; AIRMET for light occasional moderate rime ice in clouds between 8,000 to 14,000 feet. Freezing level, 5,000 feet, no change. A review of satellite data from 1730 to 1830, revealed a band of frontal convective activity moving toward the north. The line of frontal activity was positioned near the accident location about the time of the accident. COMMUNICATIONS The director of operations for the operator reported that the accident airplane pilot obtained weather information about the Kahiltna base camp by calling the base camp on the telephone. An aviation accident investigator with the U.S. Department of Interior, Office of Aircraft Services, reported that he interviewed the Kahiltna base camp manager. According to the investigator, the camp manager reported the accident airplane pilot did not telephone the base camp, and if he had called, the manager said she would have advised him to not fly to the base camp, since one airplane was already remaining on the ground due to low clouds. She did receive a telephone call about 1200 from the National Park Service Ranger who later was an occupant in the accident airplane. The base camp manager said she told the ranger "not to bother" coming to the base camp since the weather was "up and down" during the day. The base camp manager said she could hear the radio conversations between the accident airplane pilot and another airplane pilot who was then airborne after departing base camp, but soon returned to remain overnight at the camp. The manager said she then attempted to make radio contact with the accident airplane pilot, but the pilot apparently could not hear her radio transmissions. Review of the air-ground radio communication logs maintained by the National Park Service at the Talkeetna Ranger Station revealed that the National Park Ranger occupant of the airplane, communicated with the ranger station to report the flight returning to Talkeetna. No other communications from the accident airplane were noted. A search for any radar data from the area of the accident was conducted by the FAA. None was located. WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board investigator-in-charge (IIC), FAA personnel, and other parties to the investigation, examined the airplane wreckage at the accident site on June 21 and 22. The wreckage was located on a brush-covered hillside, positioned above and adjacent to lower glacier terrain. A near vertical rock face, and higher mountainous terrain was situated north of the wreckage, and the lateral moraine of a glacier was positioned south of the wreckage. Portions of the airplane were widely scattered along a wreckage path oriented along a magnetic heading of 170 degrees. (All heading/bearings noted in this report are oriented toward magnetic north.) The most northern portion of airplane wreckage found was a small portion of yellow-colored interior insulation. This was observed at the top of a rock face, about 400 feet above the lower, brush-covered hillside. No ground impact marks were observed in the area of the insulation, or along any portion of the higher terrain. Below the insulation, the airplane's left door, and the almost intact front windshield was observed resting on a small grass covered ledge, about half way up the near vertical rock face. No impact marks were observed along the entire vertical rock face, but the face was only observable by helicopter. At the base of the rock face, the left wing, separated at the inboard end, the left wing lift strut, the left landing gear strut, minus its wheel/ski assembly, the right wingtip cap, and the propeller, separate from the engine, were found along with small portions of engine accessories. Below the left wing were portions of the interior of the airplane, the right door, a broken portion of a seat track, engine components, the right wing lift strut, and one passenger. About mid-way from the base of the rock face and the southern edge of the hillside, the main portion of the fuselage was found inverted and burned. No discernable ground impact scars were found upslope, or adjacent to the fuselage point of rest. The remaining three occupants of the airplane were located in the fuselage. The engine was found at the base of a steep bank at the southern edge of the hillside, along the northern lateral moraine of a glacier. The distance from the first observed piece of interior insulation, to the fuselage point of rest, was about 1/4 mile. The distance from the base of the rock face where portions of the engine were first observed, to its point of rest at the bottom of the hill, was about 1/2 mile. The average slope of the hillside was about 40 degrees. The left wing came to rest lying flat on the ground, with the underside up. The leading edge had slight spanwise denting and scraping. About 15 gallons of fuel remained in the undamaged fuel tank. The landing lights in the leading edge were not broken. The wing tip cap was attached, but cracked. The flap and aileron remained attached to their respective attach points. The flap had a "U" shaped inward crush and tearing of the trailing edge. The inboard end of the wing had inward and upward crushing at the underside of the trailing edge. The forward wing spar was separated just outboard of the wing attach bolt and was deformed downward. The spar web material was broken and deformed downward, and twisted in a forward direction at the top of the vertical portion of the spar web. The left wing stall fence, a part of the Robertson STOL modification was found separated from the upper surface of the wing, about mid-way between the left wing and the fuselage. The right wing stall fence was not located. The left wing lift strut fitting remained attached to the wing, but the strut was separated about 8 inches from its attach point. The strut fitting was pivoted in an outboard direction at the attaching bolt, and the fitting had over-traveled beyond its normal range of motion. Denting and scuffing was noted on the underside of the wing, consistent with the lift strut striking the wing in a outboard direction, pivoting from the wing/lift strut attach point. The separated ends of the lift strut were pinched together and the fracture surfaces had tearing with 45 degree shear planes. The right wingtip cap was found next to the left wing. It was separated from the right wing and cracked. The left wing strut was found about 2 feet above the left wing. The left main landing gear strut was found under the left wing. It was separated from the fuselage at the inboard attach bolt, and the wheel/ski assembly was missing from the end of the strut. The bolts attaching the axle to the gear strut were bent and stripped of their threads. The right wing lift strut and the right cabin door were found on the ground between the left wing and the fuselage point of rest. Both the left and right lift struts were separated in a similar manner from their respective attach points. Each was about 6 feet long. Each end of the separated struts were pinched together and torn about 8 to 12 inches from each end of their respective attach points. The right cabin door hinges were torn from the fuselage. The right wing was located at the fuselage point of rest, folded over the bottom of the inverted fuselage. It was attached to the fuselage by the wing control cables. The forward right fuselage carry-through spar was separated, and had downward and forward twisting. A section of fuselage containing the aft wing attach point had downward bending of the separated fitting. The inboard portion of wing structure, and the wing fuel tank were destroyed by fire. The outboard end, with the flap and aileron assembly attached, was positioned next to and parallel to the inverted right side of the fuselage. The right wing had a chordwise tear, about mid-span, just outboard of the wing lift strut attach point. The wing spar had forward twisting at the bottom of the vertical spar web at the wing lift strut fitting. The wing aileron connect/droop push-pull tube had upward bending and was separated from the aileron bell crank. The outboard end of the right aileron, containing the balance weight, separated from the aileron, and was found mid-way between the left wing and the fuselage. The engine propeller was found in a clump of bushes, about 50 feet below the base of the upper rock face. It was separated from the engine crankshaft flange. Examination of the aft side of the hub revealed the bolt holes, into which bolts attach the propeller to the engine crankshaft flange, were stripped of their respective threads. The edge of one bolt hole had a 1/2 inch deep gouge in an outboard direction that extended for about an inch from the lip of the bolt hole, toward the outer circumference of the hub. The gou ging appeared to the full width of the bolt hole diameter. The aft side of the hub had a gouge near the center of the hub. Each of the two pilot pins, located 180 degrees from each other on the aft side of the hub, had a 45 degree impact mark on the upper end of the pin. Both propeller blades were loose in the hub. One propeller blade was bent aft about 90 degrees, about 12 inches outboard from the hub, with spanwise scratching at the point of the bend. The blade had trailing edge gouging, cupping of the tip, and slight "S" bending. The second blade had extensive, almost 300 degree aft curling of the blade, about 18 inches from the hub. It had extensive destruction and chordwise gouging at the tip. The spinner had slight aft crushing with slight twisting of the crushed metal. At the main fuselage point of rest, the left wheel/ski assembly, minus the gear strut, the right wheel/ski assembly, the right gear strut, and each respective safety cable, were located at the burned fuselage. All of the wheel/ski safety cables were either still attached to, or broken from, their respective ski, or fuselage attach points. Two cables/springs were used for the tip of each ski. A single cable was used for the aft end of each ski. Each broken end had a broom straw appearance. The forward ends of each ski assembly had fire damage, but no impact or crush damage. The airframe firewall had minor denting, but was otherwise straight. The horizontal motor mount tubes were bent and folded aft and inward. Each motor mount casting that attached the engine case to the engine mount tubing, were broken in the middle of the casting. The cockpit and cabin area, forward of the front vertical stabilizer attach point was incinerated. It came to rest at an elevation of about 3,100 feet msl. The empennage, aft of the front vertical stabilizer attach point was intact. The left horizontal stabilizer and elevator were bent and curved in a downward direction from about mid-span to the outboard tip. The outboard end of the left elevator was folded under the stabilizer. The right horizontal stabilizer was bent and curved in a downward direction from about mid-span. The elevator was similarly bent. The vertical stabilizer and the rudder were bent 90 degrees to the right about mid-height. The flight control surfaces remained connected to their respective attach points. Due to the impact and postimpact fire damage, the flight controls could not be moved by their respective control mechanisms. Flight control system cable continuity was established to the point of impact related damage in the cabin/cockpit area. The aileron/rudder cables separated ends displayed tension overload signatures. The mechanical flap assembly was burned, but the mechanism was found in the second notch (20 degrees of flap). The engine was located at the base of the hillside, at the edge of the lateral moraine, after tumbling downhill. All of the accessories were broken off, with the exception of the fuel manifold. Examination of the manifold revealed that the diaphragm was intact, the screen was free of contaminants, and the manifold contained a small amount of fuel. Portions of exhaust tubing were still attached to the engine. The tubing was extensively crushed and folded. The edges of the folded tubing were not cracked or broken. The engine crankshaft flange was not bent or gouged. The propeller bolts were still retained through their respective bolt holes. The bolts were straight, and the bolt threads had been stripped out of the propeller hub. The fuel control unit separated from the engine. The inlet fuel screen was free of contaminants. The engine fuel strainer was attached to the burned firewall. MEDICAL AND PATHOLOGICAL INFORMATION A postmortem examination of the pilot was conducted under the authority of the Alaska State Medical Examiner, 5700 E. Tudor, Anchorage, Alaska, on June 22, 2000. The cause of death for the pilot was attributed to blunt force injuries. In addition to blunt force injuries, the pilot and two passengers sustained postmortem thermal injury. One passenger, located out of the main fuselage, sustained blunt force injuries, without any thermal injury. A toxicological examination of the pilot was conducted by the FAA's Civil Aeromedical Institute (CAMI) on July 26, 2000. The examination was negative for any alcohol or drugs. FIRE A postcrash fire incinerated the cockpit and cabin area of the fuselage. SEARCH AND RESCUE On June 19, 2000, personnel from the U.S. Department of Interior, Office of Aircraft Services, contacted the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) to report the flight overdue. After the flight was reported overdue, a National Park Service climbing ranger, located at a camp at 14,000 feet on Mt. McKinley, began calling local area lodges, seeking information about the weather conditions, and any possible sighting of the airplane. The ranger was aware of the local topography, and what areas would provide the most likely egress routes from the mountain. Search aircraft located the wreckage about 1617 on June 20, 2000. The accident site was near the confluence of the Yentna and Lacuna glaciers at 3,100 feet msl, about 22 miles southwest of the Kahiltna glacier base camp. TESTS AND RESEARCH After recovery, the airframe components were reexamined on August 15, 2000, in Wasilla, Alaska. The examination confirmed that both wings separated from the fuselage in a downward direction. The engine was examined on August 16, 2000, in Palmer, Alaska. The examination did not reveal any mechanical malfunction of the engine. ADDITIONAL INFORMATION Flight activity in the vicinity of Mt. McKinley, by the National Park Service, originates primarily from Talkeetna, as does the bulk of transportation of climbers to and from the mountain by other aircraft operators. Sight seeing operations originate from Talkeetna, and a variety of locations around the park. Charter operators, and transient aircraft operating in the vicinity of Denali National Park, are requested to comply with advisory information contained in an aviation information publication, published and sponsored by the FAA Aviation Safety Program, the National Park Service, and the Alaska Aviation Safety Foundation. The advisory publication contains operating guidelines, routes, and geographic coordinates of a variety of popular locations in the park. Two radio frequencies, one for operations on the south side of the park, and one for the north side, are utilized for traffic advisories, aircraft position reports, and weather advisories between pilots. Common position reporting points for aircraft flying up the Kahiltna glacier are the toe of the Kahiltna, about 1,500 feet msl, the Big Bend of the Kahiltna, about 3,200 feet msl, and the Kahiltna Icefalls, about 6,000 feet msl. Other reporting points for entry about the midpoint of the Kahiltna glacier drainage include One Shot Gap, and South Hunter Pass. The Lacuna glacier drainage is west of the Kahiltna glacier and is separated by an area of mountain peaks and ridges. At the northern end of the Lacuna glacier, the lowest terrain between the two glacier drainages, known as the Ramparts, is about 6,500 feet msl. The terrain elevation of the ridges separating the Big Bend of the Kahiltna from the Lacuna glacier drainage, are about 4,000 to 5,000 feet msl. Additional parties to the investigation not listed on page five of this report, due to space limitations: John Kent, Teledyne Continental Motors 480 York Drive Seagoville, TX 75159 WRECKAGE RELEASE The Safety Board released the wreckage, located at Wasilla, Alaska, to the owner's representatives on October 25, 2000.

AIRCRAFT 1 FINAL REPORT

The pilot departed on a U.S. Government flight for the Department of Interior, National Parks Service, with three park rangers, in a wheel/ski equipped airplane. The airplane was operated as a VFR, on-demand air taxi flight to the Denali National Park base camp, located at 7,200 feet msl on the Kahiltna glacier. The base camp is where the three rangers were to begin mountain patrol operations on Mt. McKinley, Alaska. Variable weather conditions with low ceilings near the base camp made landing at the base camp problematic throughout the day. When the pilot departed for the base camp, he opened a VFR flight plan, and was advised that an AIRMET for mountain obscuration and turbulence were current for the area. About 45 minutes after departure, the pilot talked via radio to another airplane pilot at the Kahiltna base camp, who advised the upper portion of the glacier was closed due to low clouds. The accident pilot commented that the weather had closed the lower portion of the glacier, and he was diverting toward the west, toward another glacier drainage. A ranger on-board the accident airplane contacted his ranger station by a hand-held radio and stated the flight was returning. The accident airplane did not return to its base, and was reported overdue. The wreckage was located the following day, scattered over about 1/2 mile. Evidence indicated the airplane broke apart in-flight. The left wing, left wing lift strut, the left landing gear strut, the left door and windshield, were located on the upper portion of a steep hillside. The engine struck the ground below the left wing, separating the propeller, and then tumbled downhill. The fuselage came to rest about 1/4 mile below the left wing, and was consumed by a postcrash fire. The airplane's wing spars, and each horizontal stabilizer had all negative bending signatures. The flap handle was found extended to 20 degrees. The airplane manufacturer does not publish any negative structural load factors for a flaps down configuration. A review of meteorological data revealed an occluded front with convective activity that progressed northward toward the accident area, accompanied by heavy rain and hail. The front was positioned near the accident area when the airplane was diverting away from the mountain. The pilot was the chief pilot for the operator. The director of operations for the company has the responsibility of operational control for the operator.

AIRCRAFT 1 CAUSE REPORT

The pilot's continued flight into known adverse weather conditions and subsequent in-flight break-up. Factors in the accident were weather conditions consisting of low ceilings, turbulence, and an occluded front with convective activity, and inadequate oversight of the flight by company management.

END REPORT