19980126000599A

5099W destroyed during collision with the ground followed unknown circumstances. Night IFR IMC prevailed at time. (.4)the pilot departed on a night cross country flight at 2230 CST. The airplane did not arrive at its planned destination at 2330 CST according to the wife of the passenger. The wreckage was found about 4-miles northeast of an airport that had been reporting IFR conditions during the time period the airplane was en route and after its planned arrival. Examination of the airframe and engine revealed no mechanical anomalies that would prevent flight. The pilot's toxicology report showed about 26-percent carbon monoxide in his blood. The ends of the airplane's muffler were corroded and had many pinhole-sized holes along its edges. Its shroud had baked oil on its inside surface. The muffler had rust on both sides of its body. The airplane had flown about 4-hours during the year before the latest annual inspection had been conducted. The mechanic who had inspected the muffler said he had noticed some small pinhole-sized holes at the muffler's end. He said he did not think they were serious or would cause a problem. This inspectio n was conducted about 2-months before the accident. (-23)on January 25, 1998, at approximately 2145 CST, a Piper PA-28-160, N5099W, flown by a private pilot, departed brainerd, MN under visual flight rules (VFR) on a personal 14 CFR part 91 pleasure flight to owatonna, MN. On January 25, 1998 at approximately 2330 (CST), the aircraft was destroyed during a collision with the ground following unknown circumstances. The flight was not operating on a flight plan. Instrument meteorological conditions prvailed at the time of the accident. The operating on a flight plan. Instrument meteorological conditions prevailed at the time of the accident. The pilot and passenger were fatally injuried. Eir initiated against IA mechanic who performed annual.