Herron, WA, USA
N2534V
Cessna 170
The airplane was en route when according to the last nine minutes of radar data, the airplane descended from 3,400 to 300 feet. Sixteen days after the aircraft was reported missing Search and Rescue personnel located the airplane in a water inlet at a depth of 132 feet; 19 days later the aircraft was recovered from the accident site. A postaccident examination of the engine and the airframe revealed that the left exhaust muffler had separated at the forward seam, with evidence of sooting noted on the scat hoses surrounding the area. It was also observed that the forward end cap and exhaust riser were separated from the main body of the muffler. Magnified examinations found that almost all of the fractures were blackened and severely oxidized. The failure of the muffler was the result of undetected oxidation and cracking resulting from normal thermal degradation. The cracking would have allowed exhaust gases direct access to cabin air through the heater system. Toxicological testing of the pilot and his passenger revealed carbon monoxide levels of 45 percent and 46 percent, respectively.
HISTORY OF FLIGHT On February 29, 2004, approximately 1625 Pacific standard time, a Cessna 170 single-engine airplane, N2534V, registered to and flown by a private pilot, was destroyed during an in-flight collision with water during descent approximately one mile northwest of Herron, Washington. The pilot and his sole passenger sustained fatal injuries. Visual meteorological conditions existed, and no flight plan was filed. The cross-country flight, which was personal and operated under 14 CFR Part 91, originated from the Diamond Point Airstrip (2WA1), Sequim, Washington, approximately 1545. The flight was destined for the Auburn Municipal Airport (S50), Auburn, Washington. According to a family member the pilot departed S50 earlier in the morning for a flight to 2WA1, with a return flight to S50 scheduled later in the afternoon. According to Washington State Search and Rescue personnel, radar data indicated an aircraft departed 2WA1 at 1550 on a southerly heading and climbed to an altitude of 3,400 feet mean sea level (msl) before beginning a descent at 1615 on a south-southeasterly heading. The last recorded radar position on the aircraft was at 1624 over Case Inlet at 47 degrees 17.58 minutes north latitude, 122 degrees 49.41 minutes west longitude. This position was approximately 10 nautical miles west of the Tacoma Narrows Airport (TIW), descending from an altitude of 300 feet msl on a south-southwesterly heading. There were no radio communications between N2534V and air traffic control. Washington State Search and Rescue personnel commenced search operations the following morning after family members expressed concerns about the overdue aircraft. Positive identification of the aircraft was made on the morning of March 16, 2004. The airplane was located approximately one-half mile off of the north shoreline of Herron Island at 47 degrees 16.83 minutes north latitude, 122 degrees 49.82 minutes west longitude. Salvage personnel reported the aircraft was resting upright at a depth of 132 feet below the water's surface on a magnetic heading of 045 degrees. On April 4, 2004, the airplane was recovered and removed to a secured storage facility for further examination. PERSONNEL The pilot held a private pilot certificate with an airplane single-engine land rating. He was issued a third class medical certificate on January 22, 2004. The medical certificate application indicated that the pilot had accumulated 1,475 total flight hours, with 30 hours in the preceding 6 months. AIRCRAFT INFORMATIOIN The aircraft, serial number 18038, manufactured in 1956, was owned and operated by the pilot. According to the aircraft logbooks the airplane underwent its most recent annual inspection on September 13, 2003. The tachometer time recorded at the annual inspection was 3,839.40hours. The tachometer time recorded at the time of the accident was 3,847.09 hours. The airplane was powered by a Continental O-300-A, carbureted engine rated at 145 horsepower at 2,700 rpm. The time since major overhaul on the engine, serial number 15686-D-4-A-R, was 1,433.89 hours. METEOROLOGICAL INFORMATION At 1635, the Automated Weather Observing System located at the Bremerton National Airport, Bremerton, Washington, 13 nautical miles north of the accident site, reported wind calm, visibility 10 statue miles, few clouds at 8,000 feet, few clouds at 11,000 feet, temperature 9 degrees C, dew point 2 degrees C, with an altimeter setting of 30.00 inches of Mercury. WRECKAGE AND IMPACT INFORMATION The airplane was located intact and in an upright position submerged 132 feet below the water's surface. Subsequent to the underwater recovery process being completed, and under the supervision of a Federal Aviation Administration airworthiness inspector, flight control cable continuity was established prior to the disassembly of the aircraft. The flaps were retracted, the elevator and rudder remained attached to their respective hinges, and the control cables were traced to the cockpit area of the fuselage. Movement of the control yoke, elevator trim control, and rudder pedals resulted in appropriate movements to their respective surfaces. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot by the Pierce County Medical Examiner's Office, Tacoma, Washington. The cause of death was attributed to drowning, with contribution from carbon monoxide toxicity. Forensic toxicology was performed on the pilot by the Federal Aviation Administration Toxicology and Accident Research Laboratory, Mike Monroney Aeronautical Center, Oklahoma City, Oklahoma. The toxicology revealed 45 percent carbon monoxide was detected in the blood. The Washington State Toxicology Laboratory, Forensic Laboratory Services Bureau, Washington State Patrol, Seattle, Washington, conducted toxicology tests on the passenger. The results revealed 46 percent carbon monoxide was detected in the blood. TESTS AND RESEARCH On April 5, 2004, an examination of the aircraft was conducted under the supervision of the NTSB investigator-in-charge (IIC). Present were representatives of Cessna Aircraft Company and Teledyne Continental Motors. The engine had separated from the airframe and both propeller blades had been bent aft near their roots. The propeller rotated freely and all accessory gears rotated properly. The crankcase interior was examined through the presence of large holes, revealing all connecting rods and cam followers to be intact. The aircraft cabin heating system had been modified with the installation of a Cessna 172-style heating valve, with a two-piece muffler replacing the original exhaust system. The original cabin heating valve remained in place and did not show evidence of having been blocked. No evidence of a hose or cover of the opening, other than the valve was noted. A four-directional manifold was observed to be blocked by installation of a plate on one of the outlets. The left exhaust muffler was observed to have separated at the forward seam, and evidence of sooting was noted on the scat hoses surrounding the area. Both cabin floor heating vent covers were removed and examined. The inside of the right vent cover exhibited sooting on the tape which covered the three vent access slits. The outside of the right vent cover was void of soot and its three vent access slits were not covered. The outside and inside of the left vent cover exhibited sooting and none of the three vent access slits were covered. The fuel selector was observed in the "Both" position and a detent was observed when the handle was moved. The removal of both wings during the salvage recovery resulted in the fuel lines being compromised. The carburetor was disassembled and no evidence of a malfunction was observed. No evidence of an aircraft or engine malfunction was observed, and no evidence of a fire was detected. Metallurgical examination of the left exhaust muffler was performed by the National Transportation Safety Board, Office of Research and Engineering, Materials Laboratory Division, Washington, D.C. A Senior Metallurgist reported that the forward end cap and exhaust riser of the muffler were separated from the main body of the muffler. Matching the fractures revealed large portions of the skin were missing (see Factual Report, figure 2). Magnified examinations found that almost all of the fractures were blackened and severely oxidized. In a statement provided to the (IIC), the airframe and powerplant mechanic who performed the annual inspection on September 13, 2003, stated that during the inspection he had removed the heat shrouds and did a close visual inspection for cracks and staining by exhaust residue. The mechanic stated, "None were found at my inspection." ADDITIONAL INFORMATION The aircraft wreckage was released to the owner's representative on April 21, 2004.
The failure of the left muffler while maneuvering, resulting in a carbon monoxide leak into the cabin rendering the pilot incapacitated, and the subsequent uncontrolled descent and impact with water.
Source: NTSB Aviation Accident Database
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