The private pilot made a personal cross-country flight under Title 14, CFR Part 91 in mountainous terrain. He said that as the airplane passed near an area of steep terrain, he encountered a strong downdraft, and the airplane began to descend. He added full engine power to stop the descent, but the airplane continued to descend, and it impacted an area of down sloping tundra-covered terrain. The airplane sustained substantial damage to the fuselage, wings, and empennage. He characterized wind on the ground as light and variable, but reported encountering stronger winds just before the accident. The pilot indicated that there were no preaccident mechanical problems with the airplane, and noted in his report to the NTSB that the accident might have been avoided if he had been flying at a higher altitude, which would have provided more altitude for a recovery.