On May 29, 2009, approximately 1130 central daylight time, N31773, an experimental Gentry Chinook Plus 2 ultralight, sustained substantial damage when it collided with trees in a nose down attitude while preparing to land at the Sears private airstrip near Bridgeport, Texas. The certified flight instructor and the private pilot were seriously injured. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight conducted under 14 Code of Federal Regulations Part 91. The wife of the private pilot said that her husband had purchased the ultralight in 2008 and this was his first flight. He had been waiting until the Spring so he could go up with an instructor. The wife stated that after her husband and the instructor departed, they made two circuits around the private airstrip. While on the third circuit as the airplane turned onto the downwind leg, she saw the ultralight make a sudden left bank and pitch down. In a written statement, the flight instructor said that when he arrived at the private pilot's private airstrip they both conducted a preflight inspection of the ultralight. The instructor then proceeded to taxi up and down the runway before he departed on a short solo flight. During this flight, he performed basic turns and discovered that when a small amount of aileron input was applied he needed to apply a much larger input of rudder to maintain coordinated flight. After landing, the instructor informed the private pilot about the rudder/aileron relationship and that it would be too noisy for him to provide any instruction. The private pilot was "fine" with that and asked the instructor to make "one round" with him, and he agreed. The instructor said, "After take off, and while on downwind, I remember [the private pilot] turning around and trying to tell me something. I never did hear what he had to say. The next memory I have is seeing a large tree. I don't know if we were in the air or on the ground...All recollections after that were very intermittent." A witness said he was outside of a friend's home when he first observed the ultralight. He said it was 500 feet off the ground and about 800 yards away from where he was standing. He said the ultralight looked like it was going to land when it made a turn to the south and "nosed dived" into the ground. The witness said the engine sounded like it was "running good" and he did not observe anything wrong with the ultralight prior to the accident. A Federal Aviation Administration (FAA) inspector performed an on-scene examination of the ultralight. The inspector reported that the ultralight had been heavily fragmented from impact with the trees. He also noted that the fuel in the fuel tank had a foul odor. According to the pilot's wife, the private pilot had purchased aviation gasoline at the Bridgeport Airport last year when he bought he ultralight. She said that he had not purchased any fuel since. The reason for the foul odor could not be determined. Weather at Bridgeport Municipal Airport (XBP), Bridgeport, Texas, about six miles northwest of the accident site, at 1025, was reported as winds from 130 degrees at 3 knots, visibility 10 miles, clear skies, temperature 26 degrees Celsius, 16 degrees Celsius, and a barometric pressure setting of 30.11 inches.