On May 11, 2002, at 1620 Pacific daylight time, a Cessna 170B, N3462C, veered off runway 26R and ground looped after landing at the Brown Field Airport, San Diego, California. The airplane was operated by the flight instructor under the provisions of 14 CFR Part 91. The airplane sustained substantial damage. The airline transport licensed flight instructor, and a dual primary student were not injured. Visual meteorological conditions prevailed for the local area instructional flight that originated from Gillespie Field, El Cajon, California, at 1515. No flight plan had been filed. The winds at the time of the accident were from 300 degrees at 10 knots gusting to 15. In a telephone interview with the National Transportation Safety Board investigator-in-charge (IIC), the flight instructor reported that they entered the traffic pattern with the intention of performing touch-and-go pattern operations. The student was flying the airplane. When the airplane touched down, it began to veer to the right. By the time the flight instructor took the controls, the airplane was heading off the runway. He added power in an attempt to abort the landing. However, the airplane ground looped, impacted a ditch, and came to rest about 500 feet north of runway 26R on airport property. The instructor reported that there were no mechanical malfunctions or failures. He noted that he let the student go too far before he intervened.