Incident Summary
According to the pilot's report, after refueling the airplane, he received clearance from the tower controller to runway 21. While taxiing west toward taxiway delta, the asphalt was described as very rough, and the pilot did not see the taxiway to his left, nor an unmarked drainage ditch immediately in front of him. The airplane entered the ditch at a speed of about 5 knots.
Postaccident Examination
A postaccident examination of the airplane revealed substantial damage to the empennage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.
Airport Diagram Review
A review of the accident airport diagram showed that the area around the ditch was not a depicted taxiway. Further review of satellite imagery indicated that there were two access points to taxiway delta located southwest of the refueling point.