On June 23,1995, at 1010 hours Pacific daylight time, the pilot of a Cessna 172, N5363T, experienced mountain wave activity in the vicinity of Mount Grant and collided with the terrain near Yerington, Nevada. The aircraft was substantially damaged and the pilot and his two passengers were not injured. The aircraft departed from Yerington at 0733 hours for a local pleasure flight. According to the pilot, he was flying his passengers near an old mine to get some aerial photographs. During one of the passes, he experienced some mountain wave activity and couldn't fly the aircraft out of it. The aircraft collided with the rough terrain damaging the landing gear, both wings, and the left horizontal stabilator. After the accident, the pilot and the passengers hiked out of the area and reported the accident to the local sheriff. The elevation of Mount Grant is 11,320 feet. The pilot said he entered the canyon area at 9,500 feet. A severe downdraft brought them down into the canyon and they flew along the canyon floor as long as possible before they made a forced landing. The site elevation is at 8,500 feet. The pilot said the temperature was about 68 degrees Fahrenheit. The density altitude was approximately 11,000 feet. The pilot reported no mechanical problems. He also stated that he should have entered the mountainous terrain with more altitude and at a 45-degree angle for a better escape route.