On October 18, 1999, about 1000 eastern daylight time, a Cessna 150M, N3240V, registered to a private individual, experienced burned electrical insulation in the engine compartment inflight and was substantially damaged during a forced landing in a field near Bunnell, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight. The private-rated pilot, the sole occupant, was not injured. The flight originated about 0900, from the Orlando Executive Airport, Orlando, Florida.

The pilot stated that when abeam the Flagler County Airport he noticed that the engine abruptly began to run rough and he initiated a 180-degree turn to return and descended from 5,500 to 4,500 feet. Within 1-2 minutes he noted thick white smoke "pouring" from under the left side of the panel just underneath the magneto switch. He shut off all electrical switches including the magnetos and broadcast a "mayday" and switched the transponder to 7700. He selected a field near a farm house and flew a left hand pattern and landed in a wet grassy field. Just before the airplane came to rest, the nose landing gear dug into soft terrain and the airplane "briefly" nosed over.

According to an Federal Aviation Administration (FAA) airworthiness inspector who examined the accident site, after touchdown in a soft field, the airplane rotated to the left about the longitudinal axis damaging the main and aft spars of the right wing, coming to rest upright.

Postaccident examination of the airplane revealed heat damage to electrical wires in the engine compartment in the vicinity of the battery/battery box that is located immediately aft of the end of the right muffler. Examination of the right muffler revealed the aft end plate part number (P/N) 0450338-18, was not in place and was not located following recovery of the airplane. Additionally, the fuse for the starter relay was blown. The battery contactor and right muffler were retained for further examination.

Examination of the Contactor P/N S-1579A2, revealed no evidence of preimpact failure or malfunction. A copy of the report from Cessna Aircraft Company is an attachment to this report.

Metallurgical examination of the right muffler assembly P/N 0450400-26 by the NTSB Materials Laboratory in Washington, D.C., revealed only the peripheral flange of the aft end plate remained attached to the can; perforation of an adjacent area of the tube was noted. Examination of the fracture surface circumferentially of the remaining segment of the aft end plate revealed the surface was completely oxidized and darkened; no unoxidized fracture surface was noted. By design the thickness of the end plate is .031 inch. The remaining segment of flange of the aft end plate was measured near the fracture surface and found to be "...less than .010 inches thick over most of it's present length." The remaining flange of the aft end plate near the weld was measured and found to be .032 inch. The tube wall was measured and found to be .029 inch thick except near the area of the crevice that was measured and found to be a minimum of .011 inch thick. That area corresponded to the location of the perforation.

Four days after the accident, an FAA inspector observed a mechanic making an entry in one of the aircraft logbooks indicating completion of an annual inspection on February 1, 1999. The FAA retained the aircraft maintenance records before the entry was completed. According to the FAA certificated mechanic who reportedly performed the last annual inspection, he used 14 CFR Part 43 Appendix D, and his own manufactured inspection guide as a reference. The airplane had accumulated 3,781.4 hours total time since manufacture and approximately 37 hours since the reported completion of the last annual inspection, at the time of the accident.

The airplane owner provided copies of the aircraft and engine logbooks to the NTSB and FAA. Review of the aircraft logbook that contains entries from the production test flight dated November 27, 1974, to the last incomplete entry dated February 1, 1999, revealed the original engine installed was removed on October 15, 1975, due to a, "rod coming loose...." An engine with a different serial number was then installed. An entry dated March 1, 1977, indicates that the installed engine was removed for overhaul, and again a different engine by serial number was installed. There was no record of the right muffler being replaced or repaired. Review of the engine logbook that contains entries dated November 14, 1974, to the last entry dated January 5, 1999, revealed no entry that indicates replacement or repair of the right muffler. An entry dated September 27, 1994, indicates that the, "left exhaust" was replaced with an overhauled unit.

Review of the airplane service manual that lists in part recommended inspection intervals, revealed the intake and exhaust systems are to be generally inspected every 50 hours. The exhaust system is also recommended to be inspected visually every 100-hours of operation, or for a more thorough inspection or if fumes have been detected in the cabin, remove the muffler and pressure test under water looking for leaks. There is no requirement for a mechanic to inspect the airplane using the list provided in the service manual.

The airplane minus the retained contactor was released to the aircraft owner, Mr. James Riley, on March 23, 2000. The retained contactor was retuned via Federal Express to the owners address. Numerous attempts were unsuccessful to have the owner complete the release of parts section of NTSB Form 6120.15. Records from Federal Express indicate that "J. Riley", signed for receipt of the part on June 23, 2000, at 1253 EDT.

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