Image by Albert Lutan/ KTUU
I don't own the rights to this image. It was originally published with this story on ktuu.com

 UPDATE:

A Cessna 172 that crashed on April 20 in Birchwood, killing four people, hit a bald eagle before crashing, according to new details revealed through forensic testing by the National Transportation Safety Board.

"During the course of the investigation, which is still ongoing, a foreign substance was discovered on the airframe of the accident airplane," NTSB officials wrote in a press release Wednesday. " A forensic analysis of the substance was completed by the Smithsonian Institution in Washington, D.C., and it was determined to contain feather particles of an immature Bald Eagle."

ORIGINAL ARTICLE:

The aerial photography flight involved a series of turns near Birchwood airport the National Transportation Safety Board found in an initial report released on April 26. The Cessna 172 struck a 100-foot tall spruce tree, with the main wreckage coming to a rest nearly 500 feet away, the report says.

The plane took off from Birchwood Airport at about 8:40 a.m. and crashed just after 9 a.m. near Beach Lake Road in an area of dense spruce, birch trees and thick underbrush, officials wrote. A path of debris strewn from the tree to the main wreckage site included plexiglass, aluminum and various landing gear components.

The debris path revealed "signs of extensive fuselage fragmentation," officials wrote in the report.

The plane was registered to the pilot, 64-year-old George Kobelnyk, who was a retired Federal Aviation Administration manager. It was operated by Anchorage-based 70 North LLC.

"According to the operator's manager, the purpose of the flight was to do aerial surveying and photography over an area of land adjacent to the west edge of the airport property," officials wrote.

The three other people killed in the crash were Kobelnyk's 20-year-old co-pilot, Christian Bohrer, along with Sarah Glaves, 36 and Kyle Braun, 27.

Here is how air safety investigators described the flight path of the plane, in the preliminary report:

"Archived FAA air traffic control radar data revealed that the airplane departed from the Birchwood Airport and headed south for about 1.5 miles, then it turned west and completed a 360-degree turn at altitudes between about 1,500 to about 1,800 feet msl in an area less than a mile south of Beach Lake. The airplane then continued west toward the Knik Arm shoreline. Upon reaching the shoreline, the airplane completed a series of turning maneuvers at altitudes ranging between about 2,000 to about 2,400 feet msl before it proceeded northeast (generally along the Knik Arm shoreline), overflew the Birchwood Airport, and continued generally northeast for about 4 miles. The airplane then turned southwest, again flew over the airport, and continued southwest and back to the same area along the Knik Arm shoreline where it had completed its previous turning maneuvers. From an altitude of about 1,300 feet msl, the airplane began a right turning maneuver during which it descended to about 900 feet msl before exiting the turn about 1,100 feet msl and proceeding to the southeast. The data track showed that the airplane proceeded southeast for about 1 mile at an altitude of about 1,100 feet msl before its last data position. The last position from the radar data indicated that the airplane was about 800 feet msl, with a ground speed of about 102 knots, and traveling on about a 126-degree track."