History of Flight
On July 27, 2008, at 1439 Pacific daylight time, a Cessna 172N airplane, N75558, impacted trees and terrain while maneuvering near McMurray, Washington. The airplane was registered to Crest Airpark, Inc., Kent, Washington, and operated by the pilot under 14 CFR Part 91. The commercial pilot and two passengers were killed. The airplane was substantially damaged. Visual meteorological conditions prevailed at departure, but instrument meteorological conditions prevailed in the area at the time of the accident. No flight plan was filed. The cross-country flight originated from Roche Harbor Airport (WA09) at about 1402, with an intended destination of Auburn, Washington.
A family member reported the airplane missing to the FAA after it failed to arrive, leading to an Alert Notification. The wreckage was located by air units at approximately 2120, about 6 miles east of McMurray, in a heavily wooded mountainous area.
A witness flying a Cessna 170 reported that she observed a Cessna matching the accident airplane pass in front of her on an eastbound heading while she was receiving traffic advisories. She noted that visibility to the east appeared "very poor." No witnesses to the accident sequence were known.
Review of radar data showed the airplane initially at 2,200 to 2,500 feet msl on a southeasterly heading. At 1420, it descended to 900 feet, then climbed near Arlington Airport, performing turns with altitudes between 1,500 and 2,900 feet msl. The last radar return at 1439 recorded the airplane in a descending right-hand turn at 2,200 feet msl, 0.17 miles southwest of the accident site.
Pilot Information
The 47-year-old pilot held an airline transport pilot certificate with multiengine rating and a commercial pilot certificate with single-engine land and sea ratings. She also held a turbojet rating and type ratings in various transport-category aircraft. A first-class medical certificate was issued on November 26, 2007, with the limitation "must wear corrective lenses." She reported 14,200 total flight hours. Rental records from Crest Airpark indicated she had rented a Cessna 172 on seven occasions totaling 12.3 hours between July 2007 and July 2008, including a Cessna 172SP and a Cessna 172N within the previous 90 days (2.5 hours total).
Aircraft Information
The four-seat, high-wing, fixed-gear Cessna 172N, serial number 17267807, was manufactured in 1977. It was powered by a Lycoming O-320-H2AD engine rated at 160 horsepower, with a two-bladed fixed-pitch propeller. An annual inspection was completed on April 1, 2008, at 2,609.8 hours tachometer (9,935.4 hours airframe total time; 2,559.8 hours since engine major overhaul). At the accident, the airplane had 105.2 hours since inspection. The engine was overhauled on June 19, 2001, at 4,805.0 hours. The number four cylinder and piston were replaced on August 30, 2007, due to low compression; the replacement cylinder came from another engine that had metal found in the oil filter and suction screen in 2005.
Meteorological Conditions
At 1435, the Arlington Municipal Airport automated weather station (11 miles southwest of the accident site) reported wind from 320 degrees at 7 knots, visibility 10 statute miles, scattered clouds at 500 feet agl, broken clouds at 2,000 feet, and an overcast ceiling at 2,700 feet. Temperature was 15°C, dew point 13°C, altimeter 30.05 inches Hg. The NWS Weather Depiction Chart for 1200 showed instrument flight rules (IFR) conditions over the accident area, surrounded by marginal VFR (MVFR) conditions. The Radar Summary Chart at 1419 depicted light intensity echoes from rain showers over the region. A Skagit County Sheriff Deputy reported "spotty rain showers" and a "typical marine layer."
Communications
The pilot initially contacted Whidbey Approach Control at 1408. At 1410, the controller stated he had not seen any VFR traffic south of Bush Point in the last hour; the pilot responded that it "looks pretty good so far." At 1413, the controller instructed the pilot to maintain VFR at or above 2,500 feet msl due to traffic. At 1414, the pilot was advised to contact Whidbey on 120.70, which she did at 1415, reporting 2,500 feet. The altitude restriction was canceled at 1417. At 1419, the controller reported limited visibility and low ceilings extending north of Seattle and asked if the pilot of the accident airplane copied; the pilot acknowledged and stated they would descend to 2,000 feet. The controller replied, "maintain VFR altitudes your discretion." At 1423, radar service was terminated and the pilot was instructed to squawk VFR; she acknowledged. No further communications were received.
Wreckage and Impact
The airplane impacted trees and terrain in a heavily wooded mountainous area at an elevation of 2,214 feet msl. The wreckage came to rest on its left side on a magnetic heading of about 085 degrees. The wreckage energy path measured about 175 feet from the first identified point of contact (FIPC) with trees to the main wreckage. All major components were present. The right wing was near the FIPC with a semicircular impact 2 feet outboard of the root. The left wing and fuselage were about 100 feet beyond the right wing; the left wing had leading edge compression. The engine was separated and located 30 feet beyond the main wreckage.
Medical and Pathological Information
An autopsy performed on July 29, 2008, by the Skagit County Coroner's office determined the cause of death as blunt trauma injuries. The FAA's Civil Aeromedical Institute tested pilot toxicology; results were negative for carbon monoxide, cyanide, and volatiles. Azacyclonol was detected in the urine but not in the blood.
Engine Examination
The carburetor was examined: impact damage noted, mixture and throttle levers separated, inlet fuel fitting finger tight, fuel screen free of debris. The right float pontoon was filled with blue liquid (consistent with 100LL fuel), with a blue stain on its inner seam. No number four cylinder anomaly? Later examination revealed that the number four cylinder's exhaust valve was stuck open; tooling marks were on the rocker box casting. The exhaust valve stem was bent, and the valve guide was loose in the cylinder head. The exhaust pushrod was intact with a wear pattern consistent with contact against the dented pushrod tube. The camshaft and tappets exhibited severe wear and spalling. The crankshaft was intact and undamaged; connecting rods were undamaged. The magneto produced spark but e-gap timing was not within specifications, and points were opening slightly. The propeller blades: one bent aft about 6 inches from tip, the other bent aft and slightly curled. The engine exhibited significant internal wear consistent with a high-time engine. No airframe anomalies that would have precluded normal operation were found.