HISTORY OF FLIGHT On August 8, 1996, at 0902 central daylight time (cdt), a Lancair 320, N320L, registered to Neico Aviation, of Redmond, Oregon, piloted by a Commercial rated pilot, departed controlled flight after the propeller came off inflight, and impacted terrain, approximately four miles south of Fond Du Lac County Airport, Fond Du Lac, Wisconsin. The airplane was destroyed and the pilot sustained fatal injuries. The 14 CFR Part 91 flight was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The flight departed Wittman Regional Airport, Oshkosh, Wisconsin, at 0853 cdt. Approximately 0902 cdt, a witness near the accident site said he saw a white airplane "...spiraling downward with smoke coming from it." The witness thought that he was performing an aerobatic maneuver which is very common in that area and didn't pay much attention to it. Approximately 0905 cdt, a second witness who lives two houses away from the accident site, saw a white streak in the sky and heard an engine sputtering sound while he was on the phone. The witness then heard nothing and thought that was odd, so he went down the road and found the airplane wreckage. The airplane wreckage was discovered four miles south of Fond Du Lac Airport, by the witness who then reported it to the Fond Du Lac County Sheriff's Department at 0915 cdt. PERSONNEL INFORMATION The pilot was born April 29, 1960. He was the holder of a commercial certificate for single/multi engine land/sea rating. He held a second class medical issued on April 8, 1996. He had accumulated a total of 5,856 hours with 23 hours in this type of airplane at the time of the accident. All times are based on the last flight logbook entry made on September 23, 1995. In addition, his most recent biennial flight review is unknown. AIRCRAFT INFORMATION The airplane was a Lancair 320, serial number L 1987, N320L. The airplane had accumulated 1,501.7 hours time in service at the time of the accident. The engine had 265 hours since its last overhaul. The most recent inspection was conducted on May 11, 1995, 59 hours prior to the accident. WRECKAGE AND IMPACT INFORMATION The NTSB on-scene investigation began at 1230 on August 8, 1996. The wreckage was located four miles south of Fond Du Lac Airport, near the intersection of Lost Arrow Road and River Street. The airplane was found in a three foot high soy bean field. Examination of the accident site revealed no ground scars and an upright airplane. The engine was found in a two foot crater at a 38 degrees nose down angle and in a 9 degree left bank angle. The top of the engine cowling had oil residue running aft. The tail section also had oil residue on it. Just forward of the leading edge of the wings, there was a ground imprint similar to the shape of the leading edge of the wings that ran the full length of the wings. Pieces of the left wing position light were recovered at the end of the imprint. Examination of the wreckage revealed the fuselage was partially intact aft of the crew compartment to just forward of the empennage. The fuselage, forward of the wings, and crew compartment were fragmented. Both wings had remained attached to the fuselage. Both built-in wing tanks were ruptured. The main landing gear actuators were in the up position. The ailerons and parts from the wing sections were attached to the remaining cockpit by the aileron control cables and hydraulic lines to the main landing gear. Both leading edges of the wings had dirt residue on them and were fragmented spanwise. The left wing was fractured at a 45 degree angle from the leading edge to the aileron and flap assembly position. The tail section fractured forward of the horizontal stabilizers. The tail section was located six feet to the left rear of the main wreckage. The control cables and wiring harness were still attached to the main wreckage. The empennage remained mostly intact. The left horizontal stabilizer was fractured at the base root. The left counter weight was missing, and was located three feet in front of the tail section. The right horizontal stabilizer and elevator were undamaged. The vertical stabilizer was undamaged and the rudder was attached at the lower hinge point. The push-pull rod to the elevator was bent in several places. The elevator idler arm assembly mount had sheared midway up from the floor of the fuselage. Rudder control cables showed continuity. The propeller was not found in the engine crater nor recovered near the wreckage site. The crankshaft was sheared at the propeller flange. The crankshaft was retained for further testing. On November 19, 1996, a farmer who lives near the accident site discovered the propeller located approximately 115 degrees at 3,000 feet from the accident site while harvesting his crops. Both propeller blades and hub assembly appeared undamaged with the crankshaft flange still attached to the hub. MEDICAL AND PATHOLOGICAL INFORMATION A post mortem examination of the pilot was conducted on August 9, 1996 at Milwaukee County Medical Examiner's Office, Milwaukee, Wisconsin. No pre-existent anomalies were noted during this examination which contributed to the accident or the pilot's death. The pilot's toxicological analysis was performed by the FAA's Civil Medical Institute in Oklahoma City, Oklahoma. The toxicological examination of specimens from the pilot were negative for those drugs screened. TESTS AND RESEARCH A complete engine teardown was conducted on August 9, 1996, at Myers Aviation, Inc., of Oshkosh, Wisconsin. The intake sump originally had a rear mounted fuel servo; however, this opening was welded closed. A hole was cut in front of the oil sump where a mount for the fuel servo was welded in place, then a duct was welded up to the intake spider. Work was performed and signed off by company employees who do not hold an approved FAA Airframe and Powerplant license. The crankshaft flange was examined by the NTSB's Metallurgical Laboratory in Washington, D.C.. The NTSB metallurgist's factual report on the crankshaft flange stated "...examination of the propeller mounting flange showed that five of the six fracture areas between lightening holes contained evidence of fatigue cracking." Further examination of the fatigue cracking in the flange revealed no evidence of scratch marks, abusive machining damage, or other defects that may have contributed to the initiation of the cracking. The thickness of the propeller mounting flange was measured as 0.255 inches. A representative of Lycoming stated that the specified thickness of the propeller mounting flange on a P/N 74780 crankshaft is 0.26 inches to 0.28 inches. Hardness measurements on the flange averaged 30.4 HRC, below the specified range of 32 HRC to 36 HRC. Enclosed with this report is the Factual Metallurgist's report. The propeller mounting flanges on the crankshaft from IO-320-B1A engines installed in Piper PA-30 airplanes are the subject of Airworthiness Directive (AD) 65-03-03 (referencing Lycoming Service Bulletin 300B). This AD requires visual or magnetic particle inspection of the propeller mounting flange before the next flight following certain aerobatic type maneuvers not approved for normal category aircraft. The compliance of this AD note is not required for experimental aircraft. The Pilot's Operating Handbook for the Lancair 320 allows for aerobatic maneuvers. A radar plot displays the airplane traveling southward, south of the Fund Du Lac Airport at 3,200 feet. The airplane is observed turning back towards the north direction tracking towards the Fund Du Lac Airport. The last 10 seconds showed the airplane attitude at 2,500 feet with the last radar contact at 1,300 feet. The IIC calculated the vertical speed to have been approximately 7,200 feet per minute descent rate. Neico Aviation, Inc., calculated the weight and balance after the loss of the propeller was 1,531 pounds at 70.09 inches aft. The center of gravity envelope is between 60.75 to 66.75 inches aft. The weight and balance sheet is enclosed with this report. ADDITIONAL DATA Parties to the investigation were the Federal Aviation Administration, Neico Aviation Incorporated, and Textron Lycoming. Following the on-scene portion of the investigation, the wreckage was released to the general manager at Neico Aviation, Inc. on May 20, 1997.