HISTORY OF FLIGHT On December 12, 1999, at 1921 central standard time, a Cessna 210D, N3807Y, piloted by a commercial pilot, was destroyed on impact with terrain in a residential neighborhood. The pilot reported a vacuum failure during climb from the Spirit of Saint Louis Airport (SUS), Saint Louis, Missouri. Night instrument meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was operating on an instrument flight rules (IFR) flight plan with a filed destination of Richards-Gebaur Memorial Airport, Kansas City, Missouri. The pilot and passenger were fatally injured. The flight departed from SUS at 1915. At 0119:03, Saint Louis TRACON, Departure South (DS), transmitted, "november zero seven yankee squawk ident climb and maintain four thousand". At 1:19:04.841, radar data indicates that N3807Y's altitude was 1,900 feet msl, heading 298 degrees. At 0119:07, N3807Y transmitted, "identing climb and maintain four thousand zero seven yankee". At 1:19:09.424, radar data indicates that N3807Y's altitude was 2,000 feet msl, heading 293 degrees. At 0120:25, N3807Y transmitted, "and saint louis approach centurion zero seven yankee---with request". At 1:20:27.948, radar data indicates that N3807Y's altitude was 2,300 feet msl, heading 063 degrees. At 0120:31, DS transmitted, "zero seven yankee go ahead". At 0120:33, N3807Y transmitted, "it appears i've had a vacuum failure and i'm um uh needing a little help here". At 1:20:32.630, radar data indicates that N3807Y's altitude was 2,300 feet msl, heading 083 degrees. At 0120:39, DS transmitted, "zero seven yankee sure uh fly heading uh one eight zero and what are your flight conditions right now". At 1:20:41.807, radar data indicates that N3807Y's altitude was 2,200 feet msl, heading 121 degrees. At 0120:45, N3807Y transmitted, "and understand one eight zero zero seven yankee". At 1:20:46.308, radar data indicates that N3807Y's altitude was 2,100 feet msl, heading 146 degrees. No further transmissions were reported to have been made by N3807Y. A witness reported, "At approximately 7:20 pm on 12/12/99 my family + I were exiting our car in our driveway + heard a loud engine noise w/a little bit of reving. We all looked to the direction of the noise + realized it sounded like a small plane having trouble. It was cloudy + foggy + as we looked in the direction of the noise, (best guess is North of our house + noise was moving East to West). We saw a bright light falling fast in a diagonal descent (like a shooting star). After the light disappeared behind the rooftops we heard a very loud thud + we seemed to feel the thud as well. We then realized the plane had indeed crashed, we called 911 + drove to the area to see if my husband could help w/any survivors." A second witness reported, "...At approximately 7:15 p.m. last night, I was driving around my subdivision, Monticello Estates, with my family looking at Christmas light on the houses. We were facing a house that backs directly up to one of the lakes in The lakes subdivision. Other details that I remember are: I did not visit the scene. I happened so fast, and was dark outside that I only saw a non-strobe light on the plane as it went over our car. When I saw it, it was about 15 to 20 feet above us. About 5-10 seconds after I saw the light on the plane, I saw the light drop down vertically into The Lakes subdivision. When I saw the plane just before it went down, I still saw one of the lights on it. The weather was clear at the time but it was very dark outside. I had no problem seeing the light on the plane and there was no precipitation. The airplane was headed away from Spirit airport and was east of Highway K and North of Highway 40. It may have been trying to land at the open space behind Quik Trip and the day care facility at Highway K and O'Fallon Rd. At the same time I saw the light on the plane, I also heard the plane's engine running, but when the engine stopped, the plane quickly dropped. My car windows were up, but I did not hear an explosion and did not see any flames from the plane..." PERSONNEL INFORMATION The pilot was 43 years old and held a commercial pilot's certificate with airplane single engine land, multiengine land and instrument airplane ratings. He was issued a certified flight instructor certificate with airplane single engine and instrument airplane ratings on September 11, 1998. The pilot received a second class medical certificate with no limitations on October 13, 1999. Logbook records indicate that the pilot accumulated a total flight time of 937.8 hours of which 25.0 hours were "actual IFR" and 64.6 hours were "hooded instrument". The last logbook entry was on December 10, 1999. AIRCRAFT INFORMATION An annual/100 hour inspection of the airplane was completed on October 20, 1999 at a tachometer time of 1,023 hours, at which time 3,013 hours were logged as "time in service". METEOROLOGICAL INFORMATION At 1854, the SUS automated surface observing system, at an elevation of 462 feet msl, reported, wind 360 degrees at 5 knots, 6 smi visibility, mist, ceiling 1,400 feet overcast, temperature 6 degrees C, dew point 4 degrees C, altimeter 30.00. WRECKAGE AND IMPACT INFORMATION The main wreckage was found approximately 5.4 nmi northwest of SUS and in the yard of a single family home. An area of paint chips consistent in color with paint on the airplane was found approximately 650 feet southeast of the main wreckage. Additional wreckage lying southeast of the main wreckage consisted of a section of the right aileron's cutout located 300 feet from the main wreckage, a section of the right wing tip and skin 200 feet southeast of the main wreckage, and a section of right elevator 150 feet from the main wreckage. The engine and propeller were found next to two trees one of which was lying on the ground. The remaining tree exhibited scraping on its southeast face. The propeller was separated from the engine through a 45-degree fracture of the propeller flange. The blades displayed bending and twisting. The instrument system vacuum pump was rotated and air was expelled from the outlet side of the pump. The vacuum pump filter did not exhibit contamination. A gyro consistent with a pneumatic instrument gyro was found to display scratching about the circumference of its surface. A photo of this gyro is included in this report. An electric turn and slip indicator was found separated from the main wreckage with its needle deflected to the right and beyond the "R" position. The tachometer was found separated from the airplane and indicated 1098.22 hours. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed by the Saint Charles Medical Examiner, Saint Louis, Missouri. Federal Aviation Administration (FAA) toxicology test results reported the presence of ethanol, acetaldehyde, isopropanol, 2-butanol, and methanol. The report also stated, "The ethanol found in this case may potentially be from postmortem ethanol formation and not from the ingestion of ethanol." TEST AND RESEARCH FAA Advisory Circular 61-27C, "Illusions Leading to Spatial Disorientation", lists the major illusions leading to spatial disorientation. Several of these illusions are: "The leans" - A banked attitude to the left for example, may be entered too slowly to set in motion the fluid in the "roll" semicircular tubes. An abrupt correction of this attitude can now set the fluid in motion and so create the illusion of a banked attitude to the right... ." "Coriolis illusion" - An abrupt head movement made during a prolonged constant-rate turn may set the fluid in more than one semicircular tube in motion, creating the strong illusion of turning or accelerating in an entirely different axis... ." "Graveyard spiral" - In a prolonged coordinated, constant-rate turn, the fluid in the semicircular tubes in the axis of the turn will cease its movement (see Figure 2-1). An observed loss of altitude in the aircraft instruments and the absence of any sensation of turning may create the illusion of being in a descent with the wings level... ." "Inversion Illusion" - An abrupt change from climb to straight-and-level flight can excessively stimulate the sensory organs for gravity and linear acceleration, creating the illusion of tumbling backwards... ." ADDITIONAL INFORMATION The wreckage was released to the Saint Charles Sheriff's Department and retained parts were returned to the registered owner. The FAA and Cessna Aircraft Company were parties to the investigation.