History of Flight
On July 11, 2015, about 0745 Pacific daylight time, a Piper PA-22-160 (registration N9712D) was destroyed when it impacted the ridge of Twin Sisters Mountain, about 12 miles north of Hamilton, Washington. The aircraft was operated by the private pilot under Part 91 as a visual flight rules flight. The pilot and a single passenger sustained fatal injuries. Visual meteorological conditions prevailed; no flight plan was filed. The flight originated from Stehekin, Washington, about 0700.
The airplane was the subject of an ALNOT (alert notification) missing aircraft issued on July 14. Initial radar data showed an airplane track starting at 8,300 feet mean sea level (msl) 16 miles northwest of Stehekin at 0718. The track continued northwesterly at an altitude of about 10,500 feet msl. At 0738, the track began to descend; by 0744 the altitude was 7,500 feet. The last radar return was at 0745 at 6,000 feet msl. The wreckage was located on the morning of July 15 at the 6,000-foot level of the Twin Sisters Mountain ridge line, near the final radar return.
Personnel Information
The pilot, age 62, held a private pilot certificate with a single-engine land rating, issued May 26, 2010. He also held a third-class airman medical certificate issued February 3, 2014, with the limitation that he must possess glasses for near and intermediate vision. His logbook was not recovered. On his February 2014 medical application, he reported 440 total flight hours, with 47 hours in the previous six months.
Aircraft Information
The airplane, serial number 22-6624, was a four-seat, high-wing, fixed-gear aircraft manufactured in 1959. It was powered by a Lycoming O-360 series normally aspirated engine and equipped with a fixed-pitch propeller. Aircraft records were not located or examined.
Meteorological Information
An Automated Weather Observing System (AWOS) at Skagit Regional Airport (BVS), about 22 miles southwest of the accident site at 145 feet elevation, reported at 0735: wind variable at 5 knots, visibility 9 statute miles, ceiling broken at 4,200 feet agl, overcast at 5,000 feet agl, temperature 17°C, dew point 14°C, altimeter 29.88 inches of mercury.
WSR-88D weather radar from Seattle/Tacoma (KATX), about 36 miles southwest, showed light reflectivity values at the accident site at the accident time, consistent with light rain showers. The reflectivity features were moving from the south/southeast. An Area Forecast issued at 0345 for the Cascades forecasted broken clouds at 8,000 feet, cloud tops to FL200, scattered light rain showers, isolated thunderstorms, and cumulonimbus tops to FL350. An AIRMET for mountain obscuration was issued at 0745 and was active for the site; a prior AIRMET had been issued at 0145.
Wreckage and Impact Information
The wreckage was located near the summit of Twin Sisters Mountain at 6,000 feet msl. The site comprised two distinct sections on a steep, vegetation-free rock face. The first section included the cockpit, fuselage, left wing, and tail. The second section was the right wing. The engine had separated from its mount and was in the debris field. The propeller had separated from the engine crankshaft flange; one blade had about 4 inches of tip missing with an S-shaped trailing edge deformation, and the other blade was bent aft. The wreckage was not recovered, and no follow-up examination was performed.
Medical and Pathological Information
An autopsy of the pilot on July 17, 2015, by the Whatcom County Chief Medical Examiner determined the cause of death as multiple blunt trauma injuries. Toxicological tests by the FAA's Civil Aerospace Medical Institute were negative for ethanol and listed drugs; tests for carbon monoxide and cyanide were not conducted.