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On June 9, 1993, at 0757 central daylight time (cdt), a Beech A-36, N236A, registered to Flite Line Associates of Wauwatosa, Wisconsin, and piloted by an instrument rated private pilot, was destroyed when it experienced an inflight structural breakup. Instrument meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 flight was not operating on a flight plan. The pilot and passenger received fatal injuries. The flight originated from Waukesha, Wisconsin, at 0616 CDT.
The pilot of N236A contacted the Green Bay, Wisconsin, Automated Flight Service Station (AFSS) at 0500 cdt on June 9, 1993. The AFSS specialist advised the pilot that an AIRMET for IFR conditions existed along with occasional moderate turbulence below 12,000 feet along his intended route of flight. The pilot was advised of a low pressure area over north central Minnesota, which had an occluded front extending eastward into north central Wisconsin. During the weather briefing the AFSS specialist stated the weather was expected to improve by 0900 central daylight time.
The AFSS specialist continued the briefing, advising the pilot that "... quite a bit of rain still expected for northwestern Wisconsin and the northern two thirds-of Minnesota, and western Lake Superior areas but ... it's not supposed to be thunderstorms just rain." The specialist asked the pilot if he wanted the winds aloft and he responded, "Ah no I will probably call you as I after I'm airborne."
At 0704 CDT the pilot of N236A again contacted the AFSS at Green Bay, Wisconsin. The pilot requested a weather update for Duluth, Minnesota. The specialist advised the pilot that "... flight precautions for occasionally moderate turbulence below one two thousand with low level wind shear potential ... flight precautions ... for IFR conditions throughout northern Minnesota and the upper Peninsula IFR conditions are being reported in northern Minnesota VFR flight is not recommended... ."
The pilot contacted the same AFSS at 0754 CDT stating the airplane was positioned approximately 20 miles south of Hayward, Wisconsin, at an altitude of 10,500 feet mean sea level (msl). In addition to much of the same information given to the pilot during the earlier briefing, the AFSS specialist added the following to this briefing: "... live radar is depicting scattered light rain showers across ah northwestern Wisconsin... ." The pilot did not respond to this radio transmission. The specialist called the pilot's airplane "N" number at 0757 cdt with no response.
There were no further radio transmissions from N236A, nor were there witnesses to the airplane's descent and subsequent collision with the terrain.
The National Track Analysis Program (NTAP) data was generated by the Eagle River, Wisconsin, secondary radar site for the FAA's Minneapolis, Minnesota, Air Route Traffic Control Center (ARTCC). This site can provide data on transponder returns only. The data initially shows N236A on a northwest ground track followed by a right turn that resulted in a southeast ground track. The NTAP altitude readout data showed N236A maintaining an altitude of 10,400 feet msl while flying the northwest ground track up to the time of the pilot's radio call to the Green Bay, Wisconsin, FAA AFSS (0754:53 CDT). During the 2 minutes and 23 seconds of radio conversation that followed, the NTAP data shows N236A's altitude decreasing to 9,100 feet msl at 0757:12 CDT, at 0757:24 CDT the airplane's altitude is reported at 7,800 feet msl. After 0757:24 there were no other radar contacts.
The pilot obtained an airplane, single engine land instrument rating on July 29, 1989. At the time of issuance his logbook showed 1,308.5 hours of total flight time and 108.4 hours of instrument flying (6.1 in instrument meteorological conditions, 75.5 simulated instrument, and 26.8 hours of instrument simulator).
Pilot logbook entries between September 5, 1990, and January 4, 1991, showed the pilot flying dual instructional flights in a Beechcraft A-36. He received 34.3 hours of dual instruction in the A-36; 17.9 hours were logged as simulated instrument (hood). The last dual instruction entered in the pilot's logbook was on February 21, 1991. The logbook entry showed 1.5 hours total time, with 1.3 hours simulated instrument (hood). The last instrument reference flight made in the A-36 was on March 24, 1992, according to the pilot's logbook.
Logbook entries do not go beyond March 20, 1993. Trip sheets provided by one of the partners in N236A show the pilot's last flight, before the accident flight, was on May 20, 1993, 1.23 hours tachometer recorded time.
N236A was modified according to STC SA2200SW that allowed the installation of a Continental IO-550B engine on February 28, 1992. The engine had a McCauley 3A32C76-S-M propeller installed on it at this time.
According to the co-owners of the airplane, the weight and balance paperwork and maintenance records were kept in the airplane. Pieces of the airplane maintenance records were found along the wreckage trail. N236A received an annual inspection on June 16, 1992. At the time of inspection the airplane had 1861.6 hours total time and 72.2 hours on the engine.
According to a work order received from the Waukesha Flying Service, Incorporated, of Waukesha, Wisconsin, N236A had its engine oil changed on April 23, 1993. The air frame had 1,999.47 hours total time on this date.
No other maintenance records were located or forwarded by the co-owners of the airplane.
The Neenah, Wisconsin, weather radar site operated by the National Oceanic and Atmospheric Administration (NOAA) showed no precipitation for its coverage area from 0700 CDT to 1000 CDT. The 0830 and 0930 CDT NOAA weather radar, at Minneapolis, Minnesota, showed rain showers and light rain in extreme northwest Wisconsin, and north of Minneapolis, Minnesota. Precipitation in the accident site area was not depicted on either of the radar sites images.
The NTSB's Office of Aviation Safety confirms Minneapolis, Minnesota's, NOAA radar information by stating there were no radar echoes within 25 nautical miles of the accident site. Upper air data for the area in proximity to the accident site showed a temperature for the 672.0 millibar height (approximately 10,800 feet msl) was minus 0.1 degrees centigrade. The temperature at the 700 millibar height (approximately 9,800 feet msl) was plus 1.2 degrees centigrade.
According to the NOAA's Geostationary Operational Environmental Satellite (GOES) infrared images the temperatures at 10,337 and 10,604 feet msl were reported to be -0.54 and -0.96 degrees centigrade between 0831 and 0931 cdt respectively. Aviation surface weather sequence reports (SA) for Rice Lake, Wisconsin, show light drizzle and an altimeter setting of 29.39 inches of mercury at 1050 cdt. Rice Lake, Wisconsin, is approximately 35 nautical miles west-southwest from the accident site. The Phillips, Wisconsin, aviation surface weather sequence report for 0845 cdt showed surface winds from 210 degrees at 10 knots with gusts to 17 knots and an altimeter setting of 29.46 inches of mercury. Phillips, Wisconsin, is approximately 23 nautical miles east-northeast from the accident site.
WRECKAGE AND IMPACT INFORMATION
N236A's wreckage was scattered over a 1 1/8 statue mile trail on a south-south westerly heading through dense woods and marshy terrain. An east-west running creek ("Spring Creek") cuts the wreckage trail approximately in half. Components of the right and left elevator and horizontal stabilizer and elevators were found approximately 1,200 yards north of the engine and forward fuselage assembly.
The right wing was located approximately 50 yards north of the Spring Creek. The left wing was located on the south side of the creek, approximately 200 yards south of the right wing.
The engine and forward fuselage assemblies were at the south end of the wreckage trail. Sections of the forward fuselage, and cockpit instruments were found surrounding the engine impact crater. The fuselage center section with right and left front seats was located approximately 250 yards north of the engine impact crater.
The engine was buried approximately three feet into the marshy soil. Examination of the engine revealed internal component continuity. The crankcase was shattered from the top to the bottom rear. The vacuum pump rotated freely. The unit was separated from the engine at its mounting flange and its internal vanes were intact. The fuel pump drive shaft coupler was intact and free to rotate. Examination of the pump's internal mechanism revealed no damage. The fuel screen was clean and had an odor of 100 LL aviation fuel on it. The throttle butterfly was in the closed position. The fuel mixture control was at the mid-range position.
Two propeller blades were attached to the hub. The third blade was separated from the hub. The hub casting surrounding the propeller blade's foot was cracked with pieces separated from it.
One propeller blade was bent forward at the mid-span point. A second blade was bent aft from the hub approximately 10 degrees. Its end was "U" shaped from the mid-span point. The third blade, separated from the hub, exhibited wavelike bending. All propeller blades had spanwise and chordwise gouging of varying degrees on both surfaces and leading edges.
Instrument rotor scuff marks were observed on the turn and slip indicator's rotor and rotor mount. The airspeed indicator face stop peg was at the "0" of the 260 knot indication. The peg was bent to the right of the "0" at an approximate 30 degree angle. The airspeed indicator needle had a notch on its edge that matched with the stop peg. The heading indicator gyro rotor and case had scuff marks of their respective, adjacent, surfaces.
The attitude indicator was not found.
An examination of N236A's empennage assembly revealed both horizontal stabilizer/elevator assemblies had rotated approximately 90 degrees from their normal position on the airframe. The horizontal stabilizer's main spar was bent downward approximately 30 degrees and aft 45 degrees from the spars original position. The separated end of the spar show metal separation in tension. The elevator up and down stop points were not found.
N236A's left wing separated from the fuselage at the wing root. The fuselage center section main spar showed compression bending of the spar side walls at the separated end. The wing bolt's attach fitting at the top of the wing is bent downward. Main spar sides of the section in the wing show outward bending at the bottom. The right wing separated from the fuselage below the right front seat location. Compression bending was observed at the bottom of the spar and tension separation was observed at the top of the spar. N236A's control cables were separated in tension. Besides the broomed control cable ends, the trim tab and auto pilot cables exhibited the same type of separation.
Fuselage former cable pass through holes, guides, and areas next to the cables normal position showed metal cut through and/or cable to metal rubbing. Metal areas that were zinc chromate primed had the primer removed by scrubbing actions.
MEDICAL AND PATHOLOGICAL INFORMATION
The pilot's autopsy was conducted by the pathology department of Sacred Heart Hospital, Rusk County, Wisconsin. Toxicological samples from the pilot were examined by the U.S. Department of Defense Armed forces Institute of Pathology. The result of the examination showed no evidence of carbon monoxide, cyanide, ethanol, or drugs.
TESTS AND RESEARCH
N236A's auto-pilot was examined at the King Radio Corporation's facility located in Olathe, Kansas. An FAA avionics inspector from the Kansas City, Missouri, Flight Standards District Office participated in the examination. The tear down report is appended to this report.
Parties to the investigation were Mr. Kenneth W. Stuerke, Beech Aircraft Corporation, and Mr. John T. Kent, Teledyne Continental.
The wreckage was released to Mr. Richard Pederson, Pederson Aircraft, Incorporated, Tony, Wisconsin.