On July 24, 2018, about 1456 central daylight time (cdt), a Schmidt Vans RV7A, N20342, nosed over during landing at Princeton Municipal Airport (PNM), Princeton, Minnesota. The pilot and passenger were seriously injured, and the airplane was substantially damaged. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight originated from Mercer County Regional Airport (HZE), Hazen, North Dakota, and was destined for Wittman Regional Airport (OSH), Oshkosh Wisconsin, but diverted to PNM. The pilot and his son departed Schmidt Ranch Airport (1WN0), Northport, Washington, at 0515 Pacific daylight time, and flew to Hazen (HZE), North Dakota, and refueled. They departed HZE at 1315 cdt en route to OSH. They decided to stop in PNM for fuel. The winds were gusty. The approach to PNM was normal. When they touched down, the airplane swerved to the left, departed the runway onto soft soil, and nosed over. In his accident report, the pilot said the nose tire blew out on landing and caused the airplane to exit the runway. In an e-mail from the FAA inspector who examined the airplane, he felt that, based on ground signatures and the fact the airplane did not have a steerable nose wheel, the nose tire was flat on touchdown. He wrote: "There was a distinct long black line imprinted in the pavement from the centerline where he landed right over to the impacted runway light. The line was created by the chine that was pronounced on each side of this brand of tire. It was a gentle curve to the left off the runway with no swerving. The tire got a set in it (the sidewalls were stiffer when the flat tire was depressed with my fingers), and gentle differential braking did not affect it at all. The tire would not even roll well in the grass alongside the runway."