Webster, WI, USA
N3599F
Cessna 172L
The airplane was destroyed during a high velocity impact with terrain. The pilot was cruising at 5,500 feet when he reported a "severe vibration" and that he was diverting to a nearby airport. Aircraft radar track data was collected from radar facilities along the route of flight. The plotted data showed that the accident airplane departed the Minneapolis metropolitan area to the northeast and continued on a northerly heading toward Duluth, Minnesota. The aircraft's ground speed averaged about 100 knots while on the northerly heading. A plot of the radar data indicated that the airplane made a course reversal to a southerly heading just prior to the accident. The last radar return was approximately 0.8 nm northeast of the accident site. During the final 38 seconds of aircraft radar track data, the airplane's calculated ground speed increased from 130 knots to 218 knots while established on the southerly heading. The aircraft's maximum structural cruising speed was 121 knots and the never exceed speed was 151 knots. The current winds aloft forecast indicated that the winds at 3,000 and 6,000 feet were out of the north, between 4 and 12 knots. The wreckage was located in an open area about 950 feet long and 400 feet wide. The initial impact crater was 11 feet long, 7 feet wide and 3 feet deep. A 38 foot long ground depression ran perpendicular to the crater. The ground depression was similar in length to the accident airplane's wingspan. All primary airframe structural components, flight control surfaces, engine components, and propeller blades were located within the debris field. Fragmented wreckage was found up to 190 feet from the initial impact crater. No anomalies were noted with the airframe, flight control systems, engine, or propeller that could be associated with a pre-impact malfunction.
HISTORY OF FLIGHT On August 12, 2004, at 1545 central daylight time, a Cessna 172L, N3599F, piloted by a private pilot, was destroyed after colliding with terrain near Webster, Wisconsin. Visual meteorological conditions prevailed at the time of the accident. The flight was being operated under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot was fatally injured. The flight departed Anoka County-Blaine Airport (ANE), Minneapolis, Minnesota, at 1503 and was presumed to be en route to Duluth International Airport (DLH), Duluth, Minnesota. A timeline for the pilot's actions immediately prior to and during the accident flight was constructed using law enforcement reports in addition to transcripts and recordings provided by several Federal Aviation Administration (FAA) air traffic control facilities. The pilot met with a captain from the St. Anthony, Minnesota, Police Department between 1300 and 1400. The discussion concerned an on-going investigation into a vehicle that the pilot had recently reported as stolen. Additional information concerning the local law enforcement investigation of the alleged stolen vehicle is included with the docket information associated with this accident investigation. Subsequent to the meeting with the police captain, the pilot contacted Princeton Automated Flight Service Station (AFSS) to obtain a weather briefing for a flight from ANE to DLH. The weather briefing began at 1414:28 (hhmm:ss) and continued until 1416:52. The pilot told the briefer that his expected departure time was between 1445 and 1500. The briefer supplied a weather briefing for the proposed route of flight, including current and forecast weather conditions for the departure and arrival airports. The pilot did not file a flight plan during the weather briefing. The pilot requested and obtained clearance to depart ANE to the northeast. At 1503:33, the accident airplane was cleared to takeoff on runway 36. At 1515:59, the pilot contacted Minneapolis Approach Control and requested visual flight rules (VFR) flight following to DLH. N3599F was issued a discrete transponder code and radar contact was established at 1518:57. At 1519:21, the pilot reported that his altitude was 5,500 feet. At 1520:24, N3599F was told to contact Minneapolis Air Route Traffic Control Center (ARTCC). At 1520:49, the pilot contacted Minneapolis ARTCC and reported his altitude was 5,500 feet. At 1523:37, Minneapolis ARTCC asked the pilot what his en-route heading was to DLH. The pilot replied that he was going to fly victor airway 13 to DLH. At 1535:28, Minneapolis ARTCC informed N3599F of traffic off his left side and the pilot replied that he had visual contact with the traffic. At 1544:27, N3599F was told to contact Duluth Approach Control. The pilot immediately responded that he was "turning back to Siren [Burnett County Airport (RZN)]...we're getting a severe vibration." At 1544:41, Minneapolis ARTCC confirmed that N3599F was diverting to RZN. At 1544:53, the pilot again reported a "severe vibration." At 1544:58, Minneapolis ARTCC relayed the position of RZN to N3599F. At 1545:08, Minneapolis ARTCC relayed the current weather conditions at RZN to N3599F. At 1545:30, Minneapolis ARTCC asked the pilot if he needed any information for the approach into RZN. At 1545:37, an unidentified person said, "tell my family how much I love them" on the Minneapolis ARTCC frequency. Minneapolis ARTCC did not receive any additional communications from the accident airplane. Aircraft radar track data was collected from FAA radar facilities along the route of flight. The plotted data showed that N3599F departed the Minneapolis metropolitan area to the northeast and continued on a northerly heading toward DLH. The radar returns did not contain any altitude information. The aircraft's ground speed averaged about 100 knots while on the northerly heading. At approximately 1544:21, N3599F began a left turn to a southerly heading. At approximately 1545:08, N3599F was established on the southerly heading with a ground speed of about 130 knots. During the final 38 seconds of radar data, the airplane's calculated ground speed increased from 130 knots to 218 knots. The last radar return was recorded at 1545:46 and was approximately 0.8 nm northeast of the accident site. PERSONNEL INFORMATION According to FAA records, the pilot held a private pilot certificate with airplane single-engine land, airplane multiengine land, and instrument airplane ratings. FAA records show the pilot's last medical examination was completed on February 2, 2003, when he was issued a third-class medical certificate with no restrictions. The pilot's flight logbook was not recovered during the investigation. At the pilot's last medical examination he reported that his total flight time was 1,350 hours and he had flown 50 hours during the previous six months. AIRCRAFT INFORMATION The accident airplane was a 1971 Cessna 172L, Skyhawk, serial number 17259499. The Cessna Skyhawk is an all-metal airplane that incorporates a semimonocoque fuselage and empennage design. The airplane is equipped with externally braced wings, wing flaps, a fixed-pitch propeller, and a fixed tricycle landing gear. The airplane is configured to seat four occupants and has a certified maximum takeoff weight of 2,300 lbs. The accident airplane was issued a standard airworthiness certificate on October 21, 1970. The aircraft had a total service time of 1,496.2 hours at the time of the accident. The last annual inspection was completed on August 15, 2003, and the airplane had accumulated 6.6 hours since the inspection. The airplane was equipped with a 160 horsepower Lycoming O-320-D2G engine, serial number L-9178-39A. The O-320-D2G is a four-cylinder, 320 cubic inch displacement, carbureted, horizontally opposed, reciprocating engine. The propeller was a two-bladed McCauley 1C160/DTM7557, hub serial number 79916. METEOROLOGICAL INFORMATION The closest weather reporting station to the accident site was located at RZN, about 8.5 nm south of the accident site. The RZN Automated Weather Observing System (AWOS) recorded at 1545: Wind from 330 degrees at 6 knots; visibility 10 statute miles; scattered clouds at 5,500 feet above ground level (agl), broken ceiling at 8,500 feet agl; temperature 18 degrees Celsius; dew point 5 degrees Celsius; and altimeter 30.10 inches of mercury. WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board's on-scene investigation began on August 13, 2004. A global positioning system (GPS) receiver was used to identify the position of the main wreckage as 45-degrees 57.629-minutes north latitude, 92-degrees 19.579-minutes west longitude. The GPS elevation of the main wreckage was 1,080 feet msl. The wreckage was located in an open area about 8.5 nm north of RZN. The field was about 950 feet long and 400 feet wide. The initial impact crater was located about 290 feet from the field's northern boundary. The impact crater was 11 feet long, 7 feet wide and 3 feet deep. The impact crater was oriented on a 230 degree magnetic heading. A 38 foot long ground depression ran perpendicular to the crater. The ground depression was similar in length to the accident airplane's wingspan. Fractured portions of the propeller were found in the main crater. Three ground depressions preceded the main crater. The relative distances between these ground depressions were consistent with the accident airplane's landing gear span. The wreckage was surveyed using a GPS receiver, tape measure, and compass. The wreckage was distributed in a fan-shaped area. The centerline of the debris field was on a 220 degree magnetic heading. The limits of the fan-shaped area were between 210 and 230 degrees magnetic, with the furthest wreckage located about 190 feet from the impact point. All primary airframe structural components, flight control surfaces, engine components, and propeller blades were located within the debris field. The engine was found 42 feet from the main crater and was completely separated from its mounts and firewall. The right wing, wing-strut, and flap were found 64, 68, and 70 feet from the main crater, respectively. The main wreckage was found about 94 feet from the main crater, and consisted of the cockpit, main cabin, main landing gear legs, and empennage. The left aileron along with portions of the rear spar were found 106 feet from the main crater. One half of the propeller was found 117 feet from the main crater. The remaining portions of the left wing were found 153 feet from the main crater. The furthest piece of wreckage was the upper engine cowl which was found 190 feet from the main crater. All flight control surfaces were accounted for at the accident site. Inspection of the recovered flight control components did not reveal any evidence of pre-impact malfunction. The empennage remained partially attached to the fuselage. The elevator and aileron control surfaces remained attached to their respective hinges. The rudder remained partially attached to the vertical stabilizer and the respective hinges exhibited over travel damage. All flight control stops were examined and no repetitive strike damage was noted. Flight control cable continuity was established from the elevator to the pulley-sector located in the aft cabin. The rudder control cables were continuous from the rudder horn to the cockpit pedals. Flight control cable continuity for the left and right aileron controls could not be established due to damage. All flight control cable breaks were consistent with an overload failure. The counterweights for the rudder, elevators, and ailerons did not exhibit any evidence of pre-impact malfunction. The wing flap jackscrew position, flap selector switch, and flap position indicator were consistent with the flaps being in the fully retracted position. The engine was found separated from the fuselage firewall and its mount assembly. The engine crankshaft could not be rotated. The crankshaft was displaced about 1/8-inch aft into the crankcase. Subsequent to the removal of the rear idler gear, valve-train continuity was established by rotation of the accessory gears. The right magneto remained attached to the engine. The left magneto was separated from the engine. Both magnetos sustained impact separation of the coil and distributor block preventing operational testing. The upper sparkplugs were gray in color. The carburetor was broken and separated from the engine. The propeller was fractured through the hub and was found in three main pieces. One blade was fractured midspan. All propeller fracture features were consistent with overload. Both propeller blades exhibited chordwise scratches, leading edge damage, and spanwise twisting. All noted propeller damage was consistent with engine operation at the time of impact. No anomalies were noted with the airframe, flight control systems, engine, or propeller that could be associated with a pre-impact malfunction. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot on August 14, 2004, at the Mercy Hospital Morgue, Coon Rapids, Minnesota. Toxicology samples for the pilot were submitted to the FAA Civil Aeromedical Institute, Oklahoma City, Oklahoma. The toxicology results indicated that ethanol, methanol, and acetaldehyde were detected in the samples tested. The toxicology report noted that the detected ethanol levels originated from sources other than ingestion. TESTS AND RESEARCH During the final 38 seconds of aircraft radar track data, the airplane's calculated ground speed increased from 130 knots to 218 knots while established on a southerly heading. The Cessna 172L Type Certificate Data Sheet indicated that the maximum structural cruising speed was 121 knots and the never exceed speed was 151 knots. The current winds aloft forecast indicated that the winds at 3,000 and 6,000 feet were out of the north, between 4 and 12 knots. ADDITIONAL INFORMATION The wreckage was released to a representative of the Burnett County Sherriff's Department on August 13, 2004. Parties to the investigation included the FAA, Cessna Aircraft Company, and Lycoming.
The high velocity impact with terrain for undetermined reasons.
Source: NTSB Aviation Accident Database
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