On June 27, 2023, at 1012 central daylight time, a Velocity XLRG airplane, N340XL, was substantially damaged when it was involved in an accident near Tahlequah, Oklahoma. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he departed from the Flying Machines Airstrip (AR08) in Eureka Springs, Arkansas, on June 24, 2023, and flew to the Lawton-Fort Sill Regional Airport (LAW) in Lawton, Oklahoma. Later that same day, he departed LAW with both fuel tanks full of fuel, and attempted to fly back to AR08; however, the engine sustained a loss of power, so the pilot landed the airplane uneventfully in a field near Chickasha, Oklahoma. A mechanic examined the airframe and engine and could not determine the reason for the loss of engine power. Three days later, on June 27th, the pilot performed an engine run-up in the field and determined the engine was running properly. He departed the field and flew northeast toward AR08. The pilot stated that one hour after departure, while cruising at 10,000 ft above ground level (AGL), the engine began to misfire. He descended to 9,500 ft AGL and tried to troubleshoot the issue by leaning and richening the mixture. Doing that did not resolve the misfire, so he turned on the electric fuel pump and checked each magneto. Turning off the left magneto did not make a difference with the misfire issue; however, turning off the right magneto resulted in the power dropping off dramatically. The pilot turned the right magneto back on and increased the manifold pressure, at which time, the power dropped off completely. He landed in a field and was seriously injured. The airplane sustained substantial damage to both wings, empennage, and fuselage. Several electronic devices were removed from the airplane for examination and retrieval of recorded flight data. The electronic devices removed from the airplane were either damaged and could not be functionally tested or did not reveal any pertinent data. A review of the airframe and engine logbooks did not reveal any discrepancies of uncorrected issues with the airframe or engine. Postaccident examination revealed that the fuel cap O-rings were cracked and slightly dry-rotted. According to the airframe manufacturer, the dry-rotted O-rings may have prevented even fuel flow from the fuel tanks due to the fuel caps being non-venting, thus requiring a tight seal for proper fuel flow. However, the pilot reported that the sump tank low fuel light never came on, and there was no evidence of blue staining on top of the wings that would have indicated improperly sealed fuel caps. Due to impact damage, the engine could not be functionally tested, and the fuel system could not be examined in its entirety. The right magneto was attached to the engine; however, the body was impact damaged, and the right magneto could not be functionally tested. The left magneto was rotated by hand and a spark was produced on all leads. The postaccident examination of the airframe and fuel-injected engine revealed no mechanical failures or malfunctions that would have precluded normal operation.