Incident Summary
During the takeoff roll from a private, gravel strip that was covered with patches of snow, the pilot reported that the airplane's left main wheel 'dropped' off the gravel portion of the runway. This caused the airplane to veer to the left.
Pilot Report
The pilot stated that he continued the takeoff roll with full power, full right rudder, and 10 degrees of flaps. Despite these inputs, the nosewheel struck a soft spot on the runway, and the airplane nosed over.
Runway Conditions
The soft spot was identified by the pilot as a trench that had been excavated the previous August and had not settled completely. The runway was a private, gravel strip with patches of snow present at the time of the incident.
Outcome
The pilot reported that there was no mechanical malfunction involved in the sequence of events. The airplane nosed over after the nosewheel contacted the soft spot on the runway.