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Investigation: Plane flew steady course before Mount Si crash
A preliminary report issued by the National Transportation Safety Board on the Feb. 15 crash of a small plane suggests the Cessna 172S, with three people aboard, flew directly into Mount Si. The impact tore the wings off the plane, which was found upside down after the crash. There were no survivors.
The plane originated from the Renton Municipal Airport around 1:35 a.m. Feb. 15, according to the report, heading northeast until it approached Snoqualmie Falls, when it turned southeast, and seemed to maintain that course.
"At impact they were going roughly southeast," said NTSB investigator Wayne Pollack, who produced the report.
Pollack determined these actions of the plane by examining the Federal Aviation Administration's radar track, he said. Only one plane matching the Cessna's flight path, performance statistics, and time of disappearance, appeared on the track, making it clear that the tracked plane was the same one that crashed.
The track also indicated that the plan had initially climbed to 2,400 feet, but dropped to 1,500 feet as it approached Snoqualmie Falls. The last point on the radar track showing the plane was at 1:46 a.m., when the plane was about 1 mile southwest of the falls, and 1 mile north of I-90. At this point, the plane's groundspeed also had decreased slightly, from 112 knots to 106.
An eyewitness, who was also a private pilot, driving on I-90 at the time reported to Pollack his observations and the flight path he estimated the plane to be on. He'd observed the plane at about 1:50 a.m. flying at about 1,000 feet, well below the cloud ceiling. He lost sight of the plane briefly, and said when he spotted it again, it had changed course, traveling northeast, toward Mount Si.
Based on the time of North Bend residents' calls to 9-1-1, the impact with 4,100-foot Mount Si occurred at about 1:54 a.m. Pollack's report indicates a trail of broken branches and debris, including both wings, crushed, followed a southeasterly course to the body of the plane.
"Both wings came off during the impact with the terrain…" Pollack said, "So you have a wingless airplane fuselage coming to rest upside down."
Pollack's examination of the wreckage took one day, but the investigation is ongoing, he said. No cause will be determined until he issues his final report, which will also include findings from the autopsy of the pilot, and an examination of the plane's maintenance records.
The plane is owned by Christiansen Aviation, Inc., in Wilmington Del. The company is responsible for removing the debris, but the work has been delayed because of recent snow and rain. The trails are closed for the rest of the week.