On August 15, 2019, at 1233 central daylight time, a De Havilland DHC-6-300 airplane, N322AV, impacted runway 13 during a go-around at San Marcos Regional Airport (HYI), San Marcos, Texas. The airplane sustained substantial damage. The airline transport pilot, flight instructor, and a passenger observer received minor injuries. The airplane was registered to Wells Fargo Trust CO NA Trustee and was operated by Berry Aviation, Inc. under Title 14 Code of Federal Regulations Part 91 as a company training flight that was operating on a visual flight rules flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight originated from HYI. The airline transport pilot, seated in the left seat pilot, was receiving company training and was the flying pilot during the accident flight. The left seat pilot stated they were practicing an ILS approach for landing with a full stop on runway 13. The airplane was configured with 20° of wing flaps for landing. He said the airplane was above the glidepath, and he transitioned his scan from the flight instruments to the outside visual environment. He lowered the nose when the airplane was about 100 ft above ground level and noted the airplane was slightly left of runway centerline. He attempted to align the airplane with the centerline and thought the airplane was getting fast, so he increased the airplane pitch attitude about 50 ft above ground level. The airplane was still high when it crossed over the runway numbers and the descent rate increased. He said the flight instructor called for a go-around at the same time he decided to initiate a go-around. The left seat pilot said he attempted to add airplane energy with forward control input, which cause the airplane to pitch down with not a lot of airspeed or altitude. The left seat pilot started to increase backpressure on the flight controls and add engine power but the airplane continued to descend into the ground. The airplane struck the ground in a nose down attitude and then veered off of the runway to the left, coming to rest in the grass. The left wing and fuselage sustained substantial damage. The company/operator reported there were no mechanical anomalies that would have precluded normal airplane operation.