On July 9, 2004, about 1230 Pacific daylight time, a Petsche Kitfox 7, airplane, N1078P, sustained substantial damage subsequent to a runway excursion while landing at Arlington Municipal Airport (KAWO), Arlington, Washington. The airplane was being operated by the pilot/builder as a personal pleasure flight under Title 14, CFR Part 91, when the accident occurred. The certified private pilot and passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the cross-country flight that originated at Ellensburg, Washington. During a telephone conversation with the National Transportation Safety Board IIC, the pilot stated the airplane began to porpoise shortly after landing (wheel landing) on runway 34. The pilot stated corrective actions were taken, however, the airplane veered to the left and exited the runway. During the runway excursion, the airplane sustained substantial damage to the left wing and rudder. The METAR observation for KAWO at 1235 reported in part: winds from 240 degrees true at 7 knots; visibility 10 statute mile; scattered clouds at 2,100 feet AGL, scattered clouds at 3,200 feet; temperature 18 degrees Celsius (C); dew point 12 degrees C. At the time of the accident, a temporary FAA control tower was in operation at Arlington to facilitate the Northwest EAA Fly-In. Prior to landing, the pilot was issued a landing clearance and advised of the wind direction and speed.