What happened
On December 8, 2023, a Piper PA-18-150, registration N1880P, was involved in a fatal accident near Anchor Point, Alaska. The flight, operated under Part 91 for personal use, departed from King Salmon, Alaska, at approximately 1123 Alaska standard time. After climbing to an altitude of about 9,600 feet MSL and crossing Cook Inlet, the pilot began a descent at 1304.
As the aircraft approached the shoreline at approximately 4,500 feet MSel, the descent rate increased sharply from 1,000 feet per minute to 4,000 feet per minute. A witness reported hearing the engine RPM increase before observing the airplane in a nose-low, inverted, and spinning attitude. A dash-mounted camera from a nearby vehicle captured seven seconds of the descent, showing the aircraft in an inverted flat spin falling vertically at approximately 4,000 feet per minute. The aircraft impacted an area of low brush and trees, resulting in 2 fatal injuries for the pilot and passenger.
The investigation
Investigators examined the wreckage and found the aircraft resting inverted. While the right wing, empennage, and landing gear remained attached, the left wing's outboard section was partially separated and folded into a V-shape, though it remained attached to the fuselage by the lift struts. The aft fuselage was also compromised by a tree impact.
Mechanical examination of the Piper PA-18-150 revealed that the left wing's leading edge skin was flattened and fractured. The forward and aft spars of the left wing exhibited overstress separation and fractures. Additionally, the propeller blades showed damage, including a fracture on one blade and a missing tip on the other, consistent with impact while the engine was under power.
Analysis of the wing fabric showed multiple gouges, cuts, and scuffs. There was no evidence of tree debris within these marks, and testing by the Smithsonian Institution's Feather Identification Lab found no evidence of bird DNA on the wing or propeller. The engine was found to be in good condition with no evidence of pre-impact mechanical failure.