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On December 25, 2004, at 1021 central standard time, a Beech S35, N5631K, collided with trees and the terrain in Herman, Wisconsin, following a loss of engine power during flight. The airline transport pilot and a passenger were fatally injured. The airplane was substantially damaged by impact with the terrain and a post impact fire. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions on an instrument flight rules (IFR) flight plan. The airplane departed the Manitowoc County Airport (MTW), Manitowoc, Wisconsin, at 1010, en route to the Lewis University Airport (LOT), Romeoville, Illinois. The pilot was attempting to divert to the Sheboygan Memorial Airport (SBM), Sheboygan, Wisconsin, when the accident occurred.
Records compiled by the Federal Aviation Administration (FAA) indicate the following:
At 0545, the pilot requested weather information through a direct user access terminal (DUATS).
At 0620, the pilot filed an IFR flight plan and requested weather information through DUATS.
At 0703, the pilot called the Green Bay Flight Service Station for an IFR weather briefing for a flight from MTW to LOT.
At 1006, Green Bay (GRB) air traffic control tower (ATCT) issued an IFR clearance to N5631K for a flight from MTW to LOT.
At 1010, the pilot reported to GRB ATCT that N5631K was airborne.
At 1011, radar contact was established with N5631K.
At 1012, N5631K was issued a frequency change to contact the Chicago air route traffic control center (ZAU). At 1012:51, N5631K contacted ZAU and reported being at 4,000 feet.
At 1018:42, N5631K reported to ZAU that they had an emergency. The controller asked what the emergency was and the pilot replied that the cabin was filling with smoke and they were heading for Sheboygan.
The controller instructed N5631K to descend and maintain 3,000 feet. The controller also informed N5631K that SBM was 5 miles away at their 10 o'clock position.
At 1019:32, the controller asked the pilot if he had the airport in sight. The pilot replied that the airport was in sight.
At 1019:36, the controller cleared N5631K for the visual approach to the airport and told the pilot that he could cancel his IFR flight plan through N800MW. The pilot of N5631K responded, "three one kilo." This was the last radio contact with N5631K.
At 1025:06, another airplane reported hearing a weak ELT signal in the area.
Five witnesses were identified who either heard or saw the airplane just prior to the accident.
One witness stated his attention was drawn to the airplane by the sound of trees snapping. This witness stated he did not hear the engine running prior to the airplane contacting the trees. The witness stated that one to two minutes after the airplane impacted the ground he heard a "poof" sound and observed flames coming from the airplane. He stated that it was not an explosion.
Another witness reported seeing the airplane flying west at an altitude of about 200 feet above ground level (agl). This witness stated the engine was running rough.
A third witness reported seeing the airplane flying at an altitude of 200 to 400 feet agl. This witness stated the engine was "sputtering" and then it stopped.
A fourth witness, who was at his residence about 500 yards east of the accident site, stated he heard the airplane fly over his house. He stated the engine was very loud and that it "shook the house" as it flew overhead. This witness did not hear the impact, but did see smoke and flames coming from the field.
A resident of a farm adjacent to the accident site stated he heard the airplane fly overhead and also heard it contact the trees. This witness stated the airplane's altitude was approximately twice the height of his barn when it flew overhead. He stated the engine was running slow. He stated he noticed a "black strip" by the door.
The pilot held an airline transport pilot certificate with a multi-engine land rating. The certificate contained commercial pilot privileges for single-engine land and single-engine sea airplane ratings. The pilot also held a flight instructor certificate with single-engine land, multi-engine land, and instrument airplane ratings. His instructor certificate was last renewed on November 2, 2003.
The pilot held a third class medical issued on November 17, 2004. The medical certificate contained the limitation, "Holder shall wear lenses that correct for distant vision and possess glasses that correct for near vision. Not valid for any class after November 30, 2005."
The pilot completed Phase VII of the FAA Pilot Proficiency Wings program on September 1, 2004.
The last entry in the pilot's most recent logbook was dated December 16, 2004. According to the logbook, the pilot had a total flight time of 4,515.7 hours, of which 4,348.1 hours were logged as pilot-in-command. This logbook indicated the pilot had flown 643.3 hours in a Beech 35.
The pilot's logbook indicated that he took possession of N5631K on August 30, 2003. Since that date, the pilot logged 205.4 hours in the airplane.
N5631K was a low wing, V-tail, 1964-model Beech S35, serial number D-7389. According to FAA records, N5631K was registered to the pilot on December 13, 2003.
According to the aircraft logbook, the last annual inspection on the airplane was completed on June 16, 2004, at a tachometer time of 957.8 hours and a total aircraft time of 5,496.5 hours. The last maintenance entry in the aircraft logbook was dated December 22, 2004. This entry listed the tachometer time of 1,076.5 hours. The tachometer reading at the time of the accident was 1,076.8 hours.
The airplane was powered by a Teledyne Continental Motors IO-520-BA, serial number 280883-R. This remanufactured engine was installed in N5361K on October 9, 1993, at a tachometer time of 206.03 hours. On June 10, 1998, the cylinders were removed for a top overhaul. This occurred at a tachometer time of 696 hours which was 490 hours after the engine had been remanufactured.
The last annual inspection of the engine was on June 16, 2004, at a tachometer time of 957.8 hours. At the time of this inspection the engine total time was listed as being 751.8 hours with a time since overhaul of 261.8 hours. The entry previous to the annual inspection was for an oil change on October 6, 2003, at a tachometer time of 884.0 hours.
The mechanic who maintained the airplane stated the pilot routinely performed his own oil changes. He stated that in November 2004, the pilot informed him that there was fuel streaking down the left side of the fuselage. The mechanic stated that he inspected the airplane and did not find a fuel leak, but he did find a small oil leak.
The mechanic stated that in December 2004, the fuel return line in the right wing split, so he replaced the lines in both of the wings. He stated he also changed the push rod tube seals on the number six cylinder since the seals were leaking. He stated he wanted to replace the remainder of the push rod seals along with some other work, but the pilot wanted to wait until he returned from flying the airplane to Florida and the Bahamas.
The mechanic stated that on December 21 and 22, 2004, after the pilot returned from his trip, he replaced the sending unit gasket for the left tip tank. He stated he also installed an EZ oil sump heater. The mechanic stated that as he was inspecting the engine, he noticed the seventh stud on the number five cylinder was broken. The mechanic stated that this must have happened recently because it was not broken when he worked on the engine earlier in the month and he found the broken section of the stud in the bottom of the engine cowling. The mechanic stated he did not have the manuals or the tools to replace the stud, so they contacted an engine shop about doing the work. He stated the pilot was going to take the airplane to the engine shop following the trip to LOT.
The closest weather reporting station to the accident site was located at SBM. At 1053, the automated surface observing system (ASOS) reported wind from 220 degrees at 5 knots, visibility 7 statute miles, overcast clouds at 6,000 feet, temperature minus 9 degrees Celsius, dew point minus 4 degrees Celsius, and an altimeter setting of 30.03 inches of mercury.
WRECKAGE AND IMPACT INFORMATION
The wreckage was located in an open field at W2929 North A Highway, Herman, Wisconsin, approximately 4.2 statute miles north of SBM. The west side of the field was bordered by 30 to 40 foot tall trees. The Global Positioning System (GPS) coordinates recorded at the main wreckage using a hand held GPS unit were latitude 43 degrees 49.804 minutes north and 87 degrees 50.518 minutes west. The elevation of the terrain at the main wreckage was approximately 24 feet higher than the terrain at the tree line.
The initial impact was with the tops of the 30 to 40 foot tall trees which bordered the west edge of the field. As viewed from the ground, it appeared the trees that were initially contacted were approximately 15 feet from the edge of the field. The tree limbs found at the edge of the field were approximately two-inches in diameter. The airplane traveled approximately 294 feet after contacting the trees prior to coming to rest. The wreckage path was along a magnetic heading of 280 degrees.
The first impact mark with the terrain was approximately 90 feet from the tree line. The left wing tip tank was found near this mark. The second ground impact mark was located about 20 feet further along the wreckage path. This ground impact mark was about 10 feet in length. The magnetic compass along with pieces of the windshield and side windows were located near this area. There was no soot noted on the pieces of windshield and side window. The right main entry door was located just south of this ground impact mark. The inside surface of the door did not contain any soot and the door was in the latched position. Approximately 15 feet further along the wreckage path was another burnt ground scar.
The main wreckage came to rest inverted on a magnetic heading of 027 degrees. The fuselage was flipped to the upright position to aid in occupant removal prior to the National Transportation Safety Board's on-scene arrival.
The entire length of the right wing leading edge was crushed rearward. The outboard five feet of the wing was bent downward. The right wing did not sustain heat or fire damage. The left wing sustained substantial fire and heat damage with the bottom of the wing having been consumed. The left aileron sustained impact damage. The cockpit from the firewall up to and including the front seats sustained fire and heat damage. The cabin area behind the front seats did not sustain fire damage, but was heavily coated with soot. The right ruddervator sustained minor impact damage. The top of the left ruddervator sustained minor crush damage. The flight control cables were intact from the cockpit controls to the ruddervators and to the right wing. The flight control cables to the left wing were intact from the cockpit controls to the push rod in the wing.
The right wing main fuel tank contained fuel up to the filler cap. The left wing main fuel tank was consumed by fire. Both tip tanks were separated during the impact sequence. Both the flaps and landing gear were in the retracted position. The emergency locator transmitter activated and was turned off by personnel from SBM. The elevator trim was measured to be set at zero degrees.
A streak of oil was present under the airplane from the cockpit back to the tail. The shoulder harness buckles were not engaged. The mixture was in the idle cut off position and the throttle was pushed in to the full forward position. The propeller control was in the full forward position.
The engine was found inverted and attached to the firewall by cables and hoses. The engine was righted and moved to a hangar for inspection. The engine data plate was separated from the engine and it was found near the wreckage. The oil sump was mostly consumed by fire and heat. The propeller governor lever was in the full forward position. The throttle body was broken off of the engine. The mixture was in the idle cut off position and the throttle was full open. The accessory housing was burned. Both magnetos were in place, but the right magneto mount was broken. There were two holes in the top of the engine case. The larger of the two holes was near the number four cylinder and the smaller of the holes was abeam the larger hole and on the right side of the engine case. The journal end of the number four rod was sticking through the larger hole. The other end of the rod was connected to the piston. The number four rod journal was black in color. The seventh stud on the number five cylinder was broken off.
The engine was shipped to Teledyne Continental Motors for an in depth examination. Information from that examination can be found under the Test and Research section of this narrative.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed on the pilot by the Sheboygan County Coroner's Office, on December 27, 2004.
Toxicological tests on the pilot were conducted by the Federal Aviation Administration Toxicology Accident Research Laboratory, Oklahoma City, Oklahoma. The report stated that 0.23 (ug/ml, ug/g) of Diphenydramine was detected in the blood and Diphenhydramine was detected in the urine.
Diphenhydramine, commonly known by the trade name Benadryl, is an over-the-counter antihistamine with sedative effects, most commonly used to treat allergy symptoms.
TESTS AND RESEARCH
An examination of the engine was conducted at Teledyne Continental Motors, Mobile, Alabama, on March 8, 2005.
The examination revealed the four o'clock cylinder deck stud nuts on cylinders two, three and six cylinders were missing. The five o'clock cylinder deck stud nuts on cylinders four and five were missing. Fretting was also visible on the crankcase halves.
The crankshaft and counterweight assembly exhibited heat and impact damage at the number four connecting rod journal and forward set of counterweights. Portions of the number four connecting rod bearing were fused to the crankshaft journal. The displaced journal material moved the oil tube toward the number three main journal.
The number four connecting rod exhibited heat and mechanical damage. The rod was fractured through at the I-beam base. The connecting rod cap, both portions of the base of the I-beam, and both sets of nuts and bolts were not located.
The number two, three, and four main bearing supports mating surfaces exhibited fretting roughness. The supports exhibited a small indentation and displaced material at the mating surface from the bearing tang. The support lock slots for the number two and three main bearing supports were elongated.
All of the cylinder base packings (seals) were flattened and extruded between the cylinder mounting flanges and the crankcase cylinder deck interface. The cross section diameter of the packings was larger than a sample packing, part number 641066, which is used on IO-520-BA engines. The cross section diameter of the base packings that were removed from the engine were similar in diameter to those used on the O-470 series engines.
The certified repair station, Loth Engineering, that performed the cylinder overhaul was contacted to determine if they supplied the cylinder base packings. A representative from Loth engineering stated they did not have any records dating back to 1998. This representative stated they usually did not provide the cylinder base packing seals with cylinder overhauls.
The airframe and powerplant mechanic who removed and reinstalled the cylinders was contacted by an inspector from the FAA Milwaukee Flight Standards District Office. The mechanic stated he was working for Aircraft Maintenance Specialists (AMS) in Ocala, Florida when he removed the cylinders on N5631K. The mechanic stated that he did not remember where the packings came from. He stated they could have come from the company that rebuilt the cylinders, from a cylinder gasket package, or from the parts rooms belonging to the company that he worked for. He also stated, "Since these o-rings have no identifying number or mark on them, I would not have been able to tell the difference between an o-ring for a O-520 and a o-ring for a O-470 unless I was given both to compare."
An attempt was made to contact AMS in order to obtain additional records regarding the cylinder overhaul. It was discovered that AMS was purchased in May 2004. The current business owner provided the AMS work orders for N5631K. Loth Engineering Work Order No. 3516 indicates that they shipped 6 gasket kits with the engine. An FAA inspector from the Orlando, Florida, Flight Standards District Office visited Loth Engineering and viewed their current stock of gasket kits. These gasket kits contained the cylinder base packing seals.
Parties to the investigation were the FAA, Teledyne Continental Motors, and Raytheon Aircraft.
The wreckage was released to a representative of Western Shore Aviation on December 27, 2004. The engine was returned to Poplar Grove Airmotive by Teledyne Continental Motors on March 11, 2005.