Background
The pilot of an airplane conducted low passes over a flat, tundra site to evaluate its suitability for landing. During the second pass, the pilot touched the airplane's wheels down to verify the surface firmness before returning for a full landing.
Incident
According to the pilot, both visually and during the test-touch, the surface appeared to be "100 percent hard-surface tundra," with dry vegetation. However, near the end of the landing roll, while the airplane was traveling at about 10 mph, the wheels unexpectedly sank into "mushy" ground. The airplane then slowly nosed over.
The pilot reported no mechanical malfunctions that would have precluded normal operation. The airplane was equipped with tundra tires.
Damage
Damage to the airplane included the rudder, a strut, and wing ribs. Photographs of the airplane at the accident site showed it inverted in a broad area of flat, grassy tundra, consistent with the pilot's description.