On April 21, 2013, about 0735 eastern daylight time, a Cameron Balloons US Z-225, N65625, operated by U.S. Hot Air Balloon Team, sustained minor damage during a collision with trees and hard landing near a residence in Chester Springs, Pennsylvania. The commercial pilot and six passengers incurred minor injuries, while three passengers were seriously injured and one passenger was not injured. The local sightseeing flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the flight that departed Pottstown Municipal Airport (N47), Pottstown, Pennsylvania, about 0635. The pilot reported that he obtained a weather briefing prior to the accident flight, which departed about 30 minutes behind schedule. The departure and flight were uneventful; however, as he was preparing to land, the wind increased. The pilot attempted to land on a mowed lawn, but the balloon contacted trees just prior to the lawn. As the balloon touched down on the lawn, the gondola tipped on its side and a propane flash occurred. Several of the passengers reported that the flight departed about 30 to 60 minutes late due to a dead battery in one of the supporting ground vehicles. One passenger added that the pilot was in a hurry to takeoff as he was concerned about the increase in wind speed as the morning progressed. Two of the passengers stated that the pilot mentioned it was weird that they were the only balloon flying that morning. After flying for approximately 1 hour, the pilot wanted to land on asphalt; however, he had missed several landing spots and elected to land on grass. Just prior to landing, the pilot instructed the passengers how to brace themselves and added that the landing was going to be rough due to the wind. Passengers further stated that during the touchdown and tipping, the occupants were jostled about and out of the gondola. One passenger added that during which, something or someone fell on the burner switch, which caused a propane flash and burned three of the passengers. The other passenger injuries were described as scrapes, bruising, or muscle soreness as a result of the impact with trees and subsequent hard landing. Two of the passengers that received burns were a husband and wife, with the husband's burns more severe and to the face and head. The husband stated that during the hard landing, before the burner flash, he was yelling for someone to turn the pilot flames off. The husband and wife also reported that after the accident, the pilot asked them if they wanted him to drive them to the hospital or call 911. They both replied that they would like to be driven to the hospital. The husband later stated that he was in shock at the time and in retrospect, an ambulance would have been a better option for faster medical treatment. Several other passengers stated that once everyone was in a van, there was an approximate 5 to 10-minute delay in departing for the hospital while the pilot conferred with ground crew. One passenger stated that during that time, the pilot was pushing dirt with his feet into ground scars created by the hard landing. During a telephone interview, when asked about the wind conditions, the pilot stated that the wind was 4 to 5 knots when he launched on the accident flight and he normally would not launch if the wind was 10 to 12 knots or greater. When asked about why the pilot flames on the burners were still on during the landing, the pilot replied that the pilot flame is usually extinguished on smaller balloons prior to landing. Larger balloons, such as the accident balloon, have three burners and it takes some time to extinguish the pilot flames as it is not just a matter of moving a switch. Review of a flight manual for the accident balloon make and model revealed: "…Maximum Demonstrated Surface Wind: The maximum surface wind speed during launch and landing during FAA type certification flight tests were: For Launch 10 mph For Landing 15 mph These wind speeds are not an operating limitation..." Review of the flight manual normal procedures revealed: "…Approach to Land… Pilot light connection…shut off or popped quick release connection just before touchdown in high winds..." Review of the flight manual emergency procedures revealed: "…Preparation For a Hard Landing… Extinguish the pilot flames(s) by closing the pilot light valves(s) at the burner or by disconnecting the vapor hose quick disconnect(s) at the tanks(s)…" Heritage Field (PTW), Pottstown, Pennsylvania was located about 5 miles east of the departure point and 10 miles north of the accident site. The recorded wind at PTW, at 0554, was from 340 degrees at 7 knots. The recorded wind at 0654 was from 350 degrees at 3 knots. The recorded wind at 0754 was from 350 degrees at 9 knots, gusting to 14 knots, varying from 280 degrees to 020 degrees.