On August 24, 2003, at 1811 Pacific daylight time, a Cessna 182, N6250A, landed hard and veered off the runway at Brownsville Airport (Q21), Brownsville, California. The owner/pilot was operating the airplane under the provisions of 14 CFR Part 91. The private-pilot and the one passenger, also a private-pilot, sustained serious injuries; the airplane sustained substantial damage. Day visual meteorological conditions prevailed, and no flight plan had been filed. The local flight departed Brownsville about 1745. In a written statement, the passenger reported that the purpose of the flight was to test new radio equipment that had been installed on the airplane. During the approach to runway 24, he noted that the pilot was flying faster than normal. About 300-feet after the runway designation marking, the airplane touched down with very little flare. The airplane began to porpoise down the 20-foot wide runway. The passenger told the pilot to go-around, but the pilot responded by saying it was too late. The airplane departed off the left side of the runway and collided with a berm. It continued down a slope and slid about 200-feet, with the airplane's wings colliding with several small trees. The airplane nosed over and came to rest inverted, leaving both men hanging upside down. They were taken in a helicopter to the nearest hospital and treated for their serious injuries. During the accident the airplane incurred damage to both wings and the bottom of the fuselage. The passenger stated that the accident could have been prevented if he and the pilot had made an agreement prior to the flight that the pilot would relinquish controls to him when asked. He reported no pre-impact mechanical malfunctions or failures with the airplane.